Back in late 2004, there was a bit of excitement over asteroid 2004 MN4, which was given the highest rating on the danger scale for hitting Earth. The reason for the high rating is that it's a pretty good sized chunk of rock (400m) and not a lot of observations had been made to predict its orbit precisely. Fortunately, an impact was ruled out, just in time for the new year.
But it seems that old rumors die hard. Dispite having been poo-poo'd almost 2 years ago, sites are still reporting the danger but for a 2039 collision. Apparently they didn't read the article saying 2004 MN4 "poses no other impact probabilities with the Earth through the rest of the 21st century."
The 2004 MN4 scare isn't the only rumor that's persisted. Back in 2003, Mars made its closest approach to Earth in recorded history, giving astronomers, both professional and amateur and unprecedented view.
At that time, an Email began circulating stating that Mars would look "as big as the moon". Common sense should tell you that this is ridiculous. But amazingly enough, people started calling planetariums to find out about this event, disappointed to find out the truth.
But come summer 2004. The Email started circulating again. Snopes.com debunks it.
Summer 2005 and the Email is back!
And it seems that now, in 2006, the three year old Email is apparently still making the rounds. This time Universe Today has tackled the myth.
It seems that some people just don't get the memo. I expect that, until 2039, there will still be people saying that 2004 MN4 is still going to destroy all life on the planet, and that Mars is going to look like the moon.
Monday, July 31, 2006
Astronomy Internship - Day 52
Today's assignment was to find the center of the cluster in terms of x and y coordinates on our frame. This task conceptually wasn't too hard but did take me awhile. My method was to break the fame up into 20 columns each 100 pixels across and then count the number of stars in each one. I could then fit a 2nd order polynomial to this, take the derivative, and figure out where the peak was. Figuring out how to get Excel to do the counting for me took me awhile, but I eventually came up with a nice little trick.
I then did the same for the y axis by making rows and repeating the procedure.
Fun stuff.
I then did the same for the y axis by making rows and repeating the procedure.
Fun stuff.
Astronomy Internship - Day 51
I spent a few hours today finishing up the star matching process and sent that off to my advisor for her to play with. Aside from that, a fair amount of blogging, and playing around the net, I haven't done anything particularly exicting today.
Astronomy Internship - Day 50
As has become usual for the weekend, I've spent most of my day playing around on the internet. Exciting eh?
Astronomy Internship - Day 49
Today I was given a new task, and a tedious one at that. In order to have information about each star in all the different filters (UBVI from our data and JHK from 2MASS), we needed to match up the stars between data sets. A few stars in each were easy to identify, so Dr. Twarog worked up a coordinate transformation based on them. From there, she used that transformation on the 2MASS data to predict where the stars should be on our frame.
My task is to look at where the stars are supposed to be and see what's there. That way we can match up all the stars. It's not too difficult. Just very tiring. There's generally only one star that matches, but because our data set had so many more stars, there's a lot to sort through to find the matching ones. And there's about 550 stars to do this for.
No way I'm getting this done today. It will have to be a weekend project.
My task is to look at where the stars are supposed to be and see what's there. That way we can match up all the stars. It's not too difficult. Just very tiring. There's generally only one star that matches, but because our data set had so many more stars, there's a lot to sort through to find the matching ones. And there's about 550 stars to do this for.
No way I'm getting this done today. It will have to be a weekend project.
Sunday, July 30, 2006
The false dichotomy of gay rights
Last spring when Star Wars, Episode III hit theaters, many conservatives were up in arms because the percieved that Anakin's turning to the dark side was reminiscant of the current state of affiars in the US (dispite the outline for the script being written more than 25 years ago).
One of the more poignant lines of Anakin's that seemed to rattle conservative nerves ("Must have hit pretty close to the mark to get her all riled up like that, huh kid?") was Anakin's statement that, "If you're not with me, then you're my enemy."
This black and white world view of false dichotomies is one that is frequently held by the reiglious right.
Currently in CA, Senate Bill 1437 has been submitted which would seek to require schools to acknowledge gays throughout history in much the same way that they now regonize women, blacks, and various religious groups. Furthermore, it would prevent schools from disparaging gays.
Nowhere does this ammendment seek to actually promote homosexuality, or praise people for the sole reason that they were gay.
But that's not what conservative groups want to think. In their black and white world, if they're not allowed to slander gays and hide them from the public square, then it's promoting of the gay agenda.
But those aren't the only underhanded literary devices opponents to this bill are wanting to try. Instead of appealing to logic and sound reasoning, they blatantly work for the pathos (appeal to emotion) by claiming the bill is a "bomb dressed up as a child-caring Easter egg." No logic behind it unless you're counting logical fallacies and bifurcations. Just sick twisted appeals to gut reactions.
Yet for all their whining about agendas, they don't seem to be shy in hiding their Christian agenda when claiming that there is "a natural family -- a father, a mother, and their children."
Their argument goes on to complain about how the language is too vague in that it calls for age-appropriate teachings but doesn't state who decides this. Amazing that the law already enacted requiring age-appropriate teachings regarding "women, black Americans, American Indians, Mexicans, Asians, Pacific Island people, and other ethnic groups" doesn't specify either. But I don't see them getting their panties in a knot over that.
They claim that it will lead to indoctrination. Yet what are these good Christian parents forcing upon their children since they day they are born? Stories of eternal damnation and men getting nailed to crosses. And that somehow doesn't qualify as indoctrination? I'm seeing a double standard here.
However, if a parent wants to do that to a child, that's perfectly fine. If they want to hide their children from the reality that gays don't exist though, well, that's their right too, but they'd better keep them indoors forever because whether or not they like it "they're queer and they're here." Recongizing that fact isn't the same thing as promoting it. False dichomoties excluded of course.
One of the more poignant lines of Anakin's that seemed to rattle conservative nerves ("Must have hit pretty close to the mark to get her all riled up like that, huh kid?") was Anakin's statement that, "If you're not with me, then you're my enemy."
This black and white world view of false dichotomies is one that is frequently held by the reiglious right.
Currently in CA, Senate Bill 1437 has been submitted which would seek to require schools to acknowledge gays throughout history in much the same way that they now regonize women, blacks, and various religious groups. Furthermore, it would prevent schools from disparaging gays.
Nowhere does this ammendment seek to actually promote homosexuality, or praise people for the sole reason that they were gay.
But that's not what conservative groups want to think. In their black and white world, if they're not allowed to slander gays and hide them from the public square, then it's promoting of the gay agenda.
The March 28 amendments to SB 1437 openly REQUIRE that California public schools teach children to accept and embrace transsexuality, bisexuality, and homosexuality.Note the deceptive emphasis on REQUIRE to draw attention away from the real key words of "accept" and "embrace". The bill does neither of these but only seeks to make children "acknowledge" that *GASP* homosexuals have been around for well over 2000 years and the world hasn't ended! In fact, many famous people throughtout history have been gay.
But those aren't the only underhanded literary devices opponents to this bill are wanting to try. Instead of appealing to logic and sound reasoning, they blatantly work for the pathos (appeal to emotion) by claiming the bill is a "bomb dressed up as a child-caring Easter egg." No logic behind it unless you're counting logical fallacies and bifurcations. Just sick twisted appeals to gut reactions.
Yet for all their whining about agendas, they don't seem to be shy in hiding their Christian agenda when claiming that there is "a natural family -- a father, a mother, and their children."
Their argument goes on to complain about how the language is too vague in that it calls for age-appropriate teachings but doesn't state who decides this. Amazing that the law already enacted requiring age-appropriate teachings regarding "women, black Americans, American Indians, Mexicans, Asians, Pacific Island people, and other ethnic groups" doesn't specify either. But I don't see them getting their panties in a knot over that.
They claim that it will lead to indoctrination. Yet what are these good Christian parents forcing upon their children since they day they are born? Stories of eternal damnation and men getting nailed to crosses. And that somehow doesn't qualify as indoctrination? I'm seeing a double standard here.
However, if a parent wants to do that to a child, that's perfectly fine. If they want to hide their children from the reality that gays don't exist though, well, that's their right too, but they'd better keep them indoors forever because whether or not they like it "they're queer and they're here." Recongizing that fact isn't the same thing as promoting it. False dichomoties excluded of course.
Bush's doublespeak
It seems Bush has decided it's time to rewrite history to represent Christian egotism yet again. This time, he's declared that "In God we Trust" is now our national motto.
The statement is humorously laced with doublspeak in which he states "our country stands strong as a beacon of religious freedom." Yet it's national motto exclusively respects the Christian God? I don't see how upholding one religion and relegating all others to second class status counts as a beacon of religious freedom. Free to be short changed perhaps?
He proclaims that this motto serves "millions of Americans, [who] recognize the blessings of the Creator." But what about the 14% of the population that don't and the millions of others that don't worship his God? Are they not important?
I suppose he's not really calling all "the people of the United States to observe this day", but instead, only the ones that he actually cares about. The rest of them can piss off.
What I want to know is what happened to "E Pluribus Unum"? It'd be nice to have a national motto that could actually pass the Lemon Test.
The statement is humorously laced with doublspeak in which he states "our country stands strong as a beacon of religious freedom." Yet it's national motto exclusively respects the Christian God? I don't see how upholding one religion and relegating all others to second class status counts as a beacon of religious freedom. Free to be short changed perhaps?
He proclaims that this motto serves "millions of Americans, [who] recognize the blessings of the Creator." But what about the 14% of the population that don't and the millions of others that don't worship his God? Are they not important?
I suppose he's not really calling all "the people of the United States to observe this day", but instead, only the ones that he actually cares about. The rest of them can piss off.
What I want to know is what happened to "E Pluribus Unum"? It'd be nice to have a national motto that could actually pass the Lemon Test.
Saturday, July 29, 2006
Upholding the Seperation of Church and Sate from the Chuch's side
For an organization, whether it be a church or a non for profit, to qualify for tax exempt status one of the requirements is that they not attempt to influence legislation as a substantial part of its activities and it may not participate at all in campaign activity for or against political candidates.
But how often do we hear about megachurches singing the praises of Bush? The requirement is rarely followed, and seldom enforced since the politicians owe their very position to the churches.
That's why it's especially refreshing to see megachurch pastor preaching to uphold this. Rev. Gregory A. Boyd of the Woodland Hills Church was irritated by the repeated requests to endorse conservative political figures and causes. In response he gave a six part sermon series in which he said the church should "steer clear of politics, give up moralizing on sexual issues, stop claiming the United States as a “Christian nation” and stop glorifying American military campaigns." He insists that many Christians have lost their focus on God and instead began worshipping the false idols of the Republican party and its platform in a sort of "idolatry".
But this is not what members wanted to hear. The church lost roughly 1/5 of its members in response. Some members left saying "You’re not doing what the church is supposed to be doing, which is supporting the Republican way."
I'd recommend reading the whole article as there's many more gems in there.
But how often do we hear about megachurches singing the praises of Bush? The requirement is rarely followed, and seldom enforced since the politicians owe their very position to the churches.
That's why it's especially refreshing to see megachurch pastor preaching to uphold this. Rev. Gregory A. Boyd of the Woodland Hills Church was irritated by the repeated requests to endorse conservative political figures and causes. In response he gave a six part sermon series in which he said the church should "steer clear of politics, give up moralizing on sexual issues, stop claiming the United States as a “Christian nation” and stop glorifying American military campaigns." He insists that many Christians have lost their focus on God and instead began worshipping the false idols of the Republican party and its platform in a sort of "idolatry".
But this is not what members wanted to hear. The church lost roughly 1/5 of its members in response. Some members left saying "You’re not doing what the church is supposed to be doing, which is supporting the Republican way."
I'd recommend reading the whole article as there's many more gems in there.
The Big Bang – Common Misconceptions
Update: Due to the popularity of this post I’ve made a few changes. The first was to remove an undeveloped definition of “explosion” which excluded some events I had not previously considered. I also added a bit more information on the CMB and the WMAP results.
Update 2: Since a few people have commented regarding my strange headings in which I switched between stating the misconception and the correct representation, I have revised all the headings so that they all state the misconception.
Recently, I’ve been hanging out on some message boards and realized that, just like with evolution, there’s a lot of really uneducated people that are being very vocal about their strawman version of the Big Bang. I began to notice that their entire argument was founded on these common misconceptions and thus, I figured it was about time to make a list of the really big ones and attempt to clear them up.
This is in no way a comprehensive list, nor is it meant to present all the evidence supporting the Big Bang, but instead, only to hit the highlights.
1) The Big Bang was an explosion
This seems to be a really big one. I’ve been told that I contradict myself because I point out that the Big Bang wasn’t an explosion so I obviously don’t know what I’m talking about. The term “Big Bang” was originally given to the theory (originally called “primeval atom”) by Fred Hoyle on a radio program in which he was mocking the theory. However, the misnomer stuck and has been causing confusion ever since.
Let’s first look at what the Big Bang theory really states: “Our universe began in a hot dense state which began, and still is expanding. In this initial event, all the matter in our universe was created with approximately 80% hydrogen and 20% helium.”
That’s my personal paraphrase, but after reviewing a great number of sources, it seems to be the most comprehensive one I can come up with. So let’s analyze it. You’ll notice that nowhere do we find the word “explosion.” Instead we find the term “expansion.”
The frequent picture people seem to have is matter flying outwards from a single point (like an explosion). However, the matter is all actually standing still while space itself expands dragging the matter with it.
The general analogy for this is having a series of paperclips on a rubber band. As the rubber band is stretched, the paperclips appear to move away from one another even though they are in fact holding still with regard to the rubber band. Similarly, galaxies hold still more or less (there are small movements due to gravitational interactions) while they are carried by the expanding universe.
So again, there was no “explosion” but instead, an expansion which is carrying all the rest of the universe away from us.
2) The Big Bang theory doesn’t explain what caused it
This is another big one I see a lot. If the Big Bang was the beginning, then what could have caused the Big Bang? You’ll notice my paraphrase above didn’t include anything about this. Pretty big hole eh?
Not really. The Big Bang theory doesn’t say anything about what caused it because, well, it doesn’t need to. Theories don’t try to explain everything, just what evidence is available and pertinent. Asking the Big Bang (and Evolution) to do more than this is a double standard. After all, the theory of Gravity doesn’t explain where mass came from. The Germ theory of disease transmission doesn’t explain where germs came from. Electro-magnetic theories don’t explain where charge comes from. Atomic theory doesn’t state where atoms come from.
So while it might seem like a piece of the puzzle is missing, as far as this single theory is concerned, it’s not really important. The origin of all these other pieces requires separate theories, with their own evidence, which are being worked on, but often times, are still in their infancy (ie, brane theory to explain the precursors to the Big Bang, Abiogenesis to explain the first life…)
Additionally, the Big Bang doesn’t go all the way back because it really can’t. As I pointed out earlier, when you start going back to far, things become fuzzy. The physical laws we’re all familiar with start to break down under such high energy densities. Really weird stuff starts to happen, like different fundamental forces ceasing to exist and merging with one another.
Thanks to work in particle accelerators, which can recreate such high energy densities for brief fractions of a second, we’re starting to get a feel for how physical laws operate under these conditions, and thus, are slowly working our way backwards. But there comes a point where we just don’t have a good enough handle on things to be able to say how things work back to pretty early (10-35 seconds), but things were happening so fast and furiously, there’s still a long ways to go before we can uncover what happened to cause the whole mess.
Perhaps as better particle accelerators come on line, we’ll be able to work back even further, but this will require new theories about how matter and energy behave when shoved that close together, including a theory which has proved difficult for nearly a century, describing how gravity fits in with the other three fundamental forces into something known as the Grand Unified Theory (GUT).
3) There’s no evidence for the Big Bang
Sadly, yes, I have actually seen this one fairly often. I have no idea where people get the idea that scientists make things up without having good evidence behind it (oh wait… we’re out to disprove God because all scientists hate God or some crap like that).
The Big Bang theory does have a good amount of evidence behind it. So we’ll take a look at the three biggies.
a) Cosmological Redshift: As I explained in my earlier post, we can use spectroscopy to determine the rate at which galaxies are moving away from us. Additionally, since it takes light time to travel, the further away we look, the further back in time we are looking.
What we find, is that all galaxies in the universe are moving away from us. The further they are, the faster they’re moving away. So if we play the whole thing in reverse, all the galaxies will come back together at a single point in time. This point in time is what we call the Big Bang.
b) The Cosmic Microwave Background (CMB): Figuring that if you played everything back in time like this that all that energy would be crammed into a smaller space, that means the temperature would go up. And also since galaxies couldn’t have formed yet, we’d expect a gaseous sort of universe early on. As I discussed earlier, hot dense gasses emit photons at a peak wavelength corresponding to their temperature. Unfortunately, since things were so dense, photons couldn’t get very far.
However, with the available information, astronomers were able to determine at what density and time, photons would finally be able to get far enough that we could observe them. This is called the “surface of last scattering” and has a very specific temperature. So we should be able to look for photons with energy (wavelength) corresponding to that temperature.
But due to redshift, they will appear at a different wavelength. This radiation should appear from every direction. This was a prediction made by the Big Bang theory that was later confirmed by Penzias and Wilson who stumbled on it accidentally!
No other theory of the universe has ever been able to make such a profound prediction to the degree of accuracy the Big Bang did in this instance. Making such amazing predictions is one of the highlights of a good theory. None before or since have ever been able to pull off such a feat.
But the successes of the CMB prediction don’t stop there. Another important piece of the puzzle lies in that the CMB couldn’t be completely even. If it were, then galaxies couldn’t form since there would be no “seeds” with higher mass and thus a stronger gravitational pull to form around.
Thus, the Big Bang theory had to predict that the CMB would not be completely homogeneous. It should have some variations to it, and those variations would have to be of a specific size in order to get the universe we see today.
Early results for the Big Bang didn’t look too good for this prediction and threatened to sink the whole ship. However, the devices used were not actually sensitive enough to pick up these minute variations. But recently, with the Wilkinson Microwave Anisotropy Probe (WMAP), these perturbations have been discovered precisely as predicted.
Score two strong predictions for the Big Bang. Zero for any others.
c) Distribution of Elements: With the conceptual framework intact thanks to the first point, it was also possible to calculate how much of each element should be formed in the initial event. It should be obvious that, given a bunch of protons, electrons, and neutrons, hydrogen should be the easiest to form. Indeed, stick a proton and an electron in a room together and they’ll automatically hook up due to their magnetic attractions.
Additionally, with such high energies, it would be possible to fuse some of this hydrogen into helium and even a little bit of heavier elements. Since astronomers had a good handle on the energies, it was possible to calculate how much of each there should be. If that number didn’t match up with observations, the Big Bang theory would be shot.
Fortunately, the predictions do match up pretty closely. I stated a value earlier of 80% hydrogen, 20% helium, and neglected the rest since it would be statistically insignificant. In the universe today, we observe 75% hydrogen, 24% helium, and 1% everything else. This discrepancy is easily accounted for by nearly 14 billion years of stars cooking hydrogen into helium and other heavier elements.
So there’s three major pieces of evidence for the Big Bang, any one of which, if it had turned out any other way, would completely discredit the theory. Fortunately for the Big Bang, it has passed all of those tests, and not a single other theory has yet been able to adequately explain such things, or many anywhere near as profound of predictions (or any successful predictions for that matter). This is why the Big Bang stands alone as the premiere theory in cosmology today.
4) The Big Bang doesn’t leave room for God
This isn’t a scientific argument, but rather a philosophical one which is completely beside the point. However, since I see it used frequently, I’ll go ahead and address it.
The Big Bang, like all science, doesn’t have any implications either for or against God. What it may do, it place constraints on how God did things and these may run contrary to scripture. However, there’s two important questions here:
First off, is the scripture right in the first place? And, second, assuming it is, are you interpreting it correctly?
The first one is really beside the point given that it would be folly to approach such a topic, but the second is worth addressing. Many Christians have absolutely no problem interpreting scripture in a manner that’s completely compatible with scientific observations like the Big Bang and Evolution. In regards to the Big Bang, many people choose to interpret the “7 days” as a rather metaphorical statement in which days are better understood as “phases” and could have, in reality, been billions of years. Such people also note that Genesis’ account (roughly) follows the order in which science says things happened (although the order does differ on some points).
I think it’s also important to note that the Catholic Church has affirmed the Big Bang and finds no problem reconciling the theological and scientific perspectives on this point. Both Pope John Paul II and the Vatican’s official astronomer, George Coyne, have given strong support for the Big Bang theory. Additionally, the theory itself was originated by a Belgian priest named Georges LemaĆ®tre.
So we see, the Big Bang can fit well with scripture so long as one is willing to look at things from the right point of view.
I hope that clears up a few of the misconceptions people have been having, and I’m pretty sure that most people reading this blog were already familiar with all that, but perhaps this has given you a bit more detailed information that you can use next time someone throws out their strawman Big Bang.
Update 2: Since a few people have commented regarding my strange headings in which I switched between stating the misconception and the correct representation, I have revised all the headings so that they all state the misconception.
Recently, I’ve been hanging out on some message boards and realized that, just like with evolution, there’s a lot of really uneducated people that are being very vocal about their strawman version of the Big Bang. I began to notice that their entire argument was founded on these common misconceptions and thus, I figured it was about time to make a list of the really big ones and attempt to clear them up.
This is in no way a comprehensive list, nor is it meant to present all the evidence supporting the Big Bang, but instead, only to hit the highlights.
1) The Big Bang was an explosion
This seems to be a really big one. I’ve been told that I contradict myself because I point out that the Big Bang wasn’t an explosion so I obviously don’t know what I’m talking about. The term “Big Bang” was originally given to the theory (originally called “primeval atom”) by Fred Hoyle on a radio program in which he was mocking the theory. However, the misnomer stuck and has been causing confusion ever since.
Let’s first look at what the Big Bang theory really states: “Our universe began in a hot dense state which began, and still is expanding. In this initial event, all the matter in our universe was created with approximately 80% hydrogen and 20% helium.”
That’s my personal paraphrase, but after reviewing a great number of sources, it seems to be the most comprehensive one I can come up with. So let’s analyze it. You’ll notice that nowhere do we find the word “explosion.” Instead we find the term “expansion.”
The frequent picture people seem to have is matter flying outwards from a single point (like an explosion). However, the matter is all actually standing still while space itself expands dragging the matter with it.
The general analogy for this is having a series of paperclips on a rubber band. As the rubber band is stretched, the paperclips appear to move away from one another even though they are in fact holding still with regard to the rubber band. Similarly, galaxies hold still more or less (there are small movements due to gravitational interactions) while they are carried by the expanding universe.
So again, there was no “explosion” but instead, an expansion which is carrying all the rest of the universe away from us.
2) The Big Bang theory doesn’t explain what caused it
This is another big one I see a lot. If the Big Bang was the beginning, then what could have caused the Big Bang? You’ll notice my paraphrase above didn’t include anything about this. Pretty big hole eh?
Not really. The Big Bang theory doesn’t say anything about what caused it because, well, it doesn’t need to. Theories don’t try to explain everything, just what evidence is available and pertinent. Asking the Big Bang (and Evolution) to do more than this is a double standard. After all, the theory of Gravity doesn’t explain where mass came from. The Germ theory of disease transmission doesn’t explain where germs came from. Electro-magnetic theories don’t explain where charge comes from. Atomic theory doesn’t state where atoms come from.
So while it might seem like a piece of the puzzle is missing, as far as this single theory is concerned, it’s not really important. The origin of all these other pieces requires separate theories, with their own evidence, which are being worked on, but often times, are still in their infancy (ie, brane theory to explain the precursors to the Big Bang, Abiogenesis to explain the first life…)
Additionally, the Big Bang doesn’t go all the way back because it really can’t. As I pointed out earlier, when you start going back to far, things become fuzzy. The physical laws we’re all familiar with start to break down under such high energy densities. Really weird stuff starts to happen, like different fundamental forces ceasing to exist and merging with one another.
Thanks to work in particle accelerators, which can recreate such high energy densities for brief fractions of a second, we’re starting to get a feel for how physical laws operate under these conditions, and thus, are slowly working our way backwards. But there comes a point where we just don’t have a good enough handle on things to be able to say how things work back to pretty early (10-35 seconds), but things were happening so fast and furiously, there’s still a long ways to go before we can uncover what happened to cause the whole mess.
Perhaps as better particle accelerators come on line, we’ll be able to work back even further, but this will require new theories about how matter and energy behave when shoved that close together, including a theory which has proved difficult for nearly a century, describing how gravity fits in with the other three fundamental forces into something known as the Grand Unified Theory (GUT).
3) There’s no evidence for the Big Bang
Sadly, yes, I have actually seen this one fairly often. I have no idea where people get the idea that scientists make things up without having good evidence behind it (oh wait… we’re out to disprove God because all scientists hate God or some crap like that).
The Big Bang theory does have a good amount of evidence behind it. So we’ll take a look at the three biggies.
a) Cosmological Redshift: As I explained in my earlier post, we can use spectroscopy to determine the rate at which galaxies are moving away from us. Additionally, since it takes light time to travel, the further away we look, the further back in time we are looking.
What we find, is that all galaxies in the universe are moving away from us. The further they are, the faster they’re moving away. So if we play the whole thing in reverse, all the galaxies will come back together at a single point in time. This point in time is what we call the Big Bang.
b) The Cosmic Microwave Background (CMB): Figuring that if you played everything back in time like this that all that energy would be crammed into a smaller space, that means the temperature would go up. And also since galaxies couldn’t have formed yet, we’d expect a gaseous sort of universe early on. As I discussed earlier, hot dense gasses emit photons at a peak wavelength corresponding to their temperature. Unfortunately, since things were so dense, photons couldn’t get very far.
However, with the available information, astronomers were able to determine at what density and time, photons would finally be able to get far enough that we could observe them. This is called the “surface of last scattering” and has a very specific temperature. So we should be able to look for photons with energy (wavelength) corresponding to that temperature.
But due to redshift, they will appear at a different wavelength. This radiation should appear from every direction. This was a prediction made by the Big Bang theory that was later confirmed by Penzias and Wilson who stumbled on it accidentally!
No other theory of the universe has ever been able to make such a profound prediction to the degree of accuracy the Big Bang did in this instance. Making such amazing predictions is one of the highlights of a good theory. None before or since have ever been able to pull off such a feat.
But the successes of the CMB prediction don’t stop there. Another important piece of the puzzle lies in that the CMB couldn’t be completely even. If it were, then galaxies couldn’t form since there would be no “seeds” with higher mass and thus a stronger gravitational pull to form around.
Thus, the Big Bang theory had to predict that the CMB would not be completely homogeneous. It should have some variations to it, and those variations would have to be of a specific size in order to get the universe we see today.
Early results for the Big Bang didn’t look too good for this prediction and threatened to sink the whole ship. However, the devices used were not actually sensitive enough to pick up these minute variations. But recently, with the Wilkinson Microwave Anisotropy Probe (WMAP), these perturbations have been discovered precisely as predicted.
Score two strong predictions for the Big Bang. Zero for any others.
c) Distribution of Elements: With the conceptual framework intact thanks to the first point, it was also possible to calculate how much of each element should be formed in the initial event. It should be obvious that, given a bunch of protons, electrons, and neutrons, hydrogen should be the easiest to form. Indeed, stick a proton and an electron in a room together and they’ll automatically hook up due to their magnetic attractions.
Additionally, with such high energies, it would be possible to fuse some of this hydrogen into helium and even a little bit of heavier elements. Since astronomers had a good handle on the energies, it was possible to calculate how much of each there should be. If that number didn’t match up with observations, the Big Bang theory would be shot.
Fortunately, the predictions do match up pretty closely. I stated a value earlier of 80% hydrogen, 20% helium, and neglected the rest since it would be statistically insignificant. In the universe today, we observe 75% hydrogen, 24% helium, and 1% everything else. This discrepancy is easily accounted for by nearly 14 billion years of stars cooking hydrogen into helium and other heavier elements.
So there’s three major pieces of evidence for the Big Bang, any one of which, if it had turned out any other way, would completely discredit the theory. Fortunately for the Big Bang, it has passed all of those tests, and not a single other theory has yet been able to adequately explain such things, or many anywhere near as profound of predictions (or any successful predictions for that matter). This is why the Big Bang stands alone as the premiere theory in cosmology today.
4) The Big Bang doesn’t leave room for God
This isn’t a scientific argument, but rather a philosophical one which is completely beside the point. However, since I see it used frequently, I’ll go ahead and address it.
The Big Bang, like all science, doesn’t have any implications either for or against God. What it may do, it place constraints on how God did things and these may run contrary to scripture. However, there’s two important questions here:
First off, is the scripture right in the first place? And, second, assuming it is, are you interpreting it correctly?
The first one is really beside the point given that it would be folly to approach such a topic, but the second is worth addressing. Many Christians have absolutely no problem interpreting scripture in a manner that’s completely compatible with scientific observations like the Big Bang and Evolution. In regards to the Big Bang, many people choose to interpret the “7 days” as a rather metaphorical statement in which days are better understood as “phases” and could have, in reality, been billions of years. Such people also note that Genesis’ account (roughly) follows the order in which science says things happened (although the order does differ on some points).
I think it’s also important to note that the Catholic Church has affirmed the Big Bang and finds no problem reconciling the theological and scientific perspectives on this point. Both Pope John Paul II and the Vatican’s official astronomer, George Coyne, have given strong support for the Big Bang theory. Additionally, the theory itself was originated by a Belgian priest named Georges LemaĆ®tre.
So we see, the Big Bang can fit well with scripture so long as one is willing to look at things from the right point of view.
I hope that clears up a few of the misconceptions people have been having, and I’m pretty sure that most people reading this blog were already familiar with all that, but perhaps this has given you a bit more detailed information that you can use next time someone throws out their strawman Big Bang.
Friday, July 28, 2006
One expensive playhouse
In 2004, Bush announced his "Space Vision." At the time, I was in a planetary geology class and we had an assignment to review the proposal and give our opinions on it.
In short, the entire class found it pretty short sighted, mainly due to massive under funding. Sure enough, within months, experts from many places agreed that the goals were unattainable with current levels of funding. Bush did increase the funding by a good amount, but not nearly what experts predicted NASA would need to accomplish the goals.
Unless other cuts were made. But to where?
Science of course! Since then, several science missions have been shelved or scrapped all together. Many grants (including the Missouri Space Grant Consortium which one of my friends does research thanks to), were threatened. Although NASA denied it, many people thought the sudden cancellation of servicing the Hubble was in large part due to budget strains.
So while I have no problem with going back to the Moon or Mars, I would just like to see things properly funded. Perhaps not to the 1% of the national budget that it recieved during the hay day of the Apollo program, but definately to a better extent than it currently is.
This topic came up recently on one of the internet forums I frequent, and just as I posted my opinions this article comes out as if too add an exclamation point to all of my statements.
In short, NASA is considering suspending American science research on the ISS in order to save money while they finish building another module.
My question is, without science, what good is the ISS? Suddenly, it's a gigantic, $100 billion, 360km high tree house. What a waste.
In short, the entire class found it pretty short sighted, mainly due to massive under funding. Sure enough, within months, experts from many places agreed that the goals were unattainable with current levels of funding. Bush did increase the funding by a good amount, but not nearly what experts predicted NASA would need to accomplish the goals.
Unless other cuts were made. But to where?
Science of course! Since then, several science missions have been shelved or scrapped all together. Many grants (including the Missouri Space Grant Consortium which one of my friends does research thanks to), were threatened. Although NASA denied it, many people thought the sudden cancellation of servicing the Hubble was in large part due to budget strains.
So while I have no problem with going back to the Moon or Mars, I would just like to see things properly funded. Perhaps not to the 1% of the national budget that it recieved during the hay day of the Apollo program, but definately to a better extent than it currently is.
This topic came up recently on one of the internet forums I frequent, and just as I posted my opinions this article comes out as if too add an exclamation point to all of my statements.
In short, NASA is considering suspending American science research on the ISS in order to save money while they finish building another module.
My question is, without science, what good is the ISS? Suddenly, it's a gigantic, $100 billion, 360km high tree house. What a waste.
Astronomy Internship - Day 48
As predicted, I spent my day making light curves for the new canidates. Most of them don't look like anything, but there's a few that show some nice trends and should bear further investigation.
I've also noticed that the data from the second night seems to be about 1/2 a magnitude fainter than the first. If I were just looking at one star, I'd think that it was due to a variablility in the star, but it's in almost every star. The calibration should have accounted for this, so the discrepancy may be something that we'll need to look into a bit more.
I've also noticed that the data from the second night seems to be about 1/2 a magnitude fainter than the first. If I were just looking at one star, I'd think that it was due to a variablility in the star, but it's in almost every star. The calibration should have accounted for this, so the discrepancy may be something that we'll need to look into a bit more.
Astronomy Internship - Day 47
I ended up spending a good portion of my day today trying to get things squared away for the upcoming semester: Housing, tuition payment program, figuring out things for the FAFSA. Thus, I didn't get started on my project until late this afternoon. But since my main goal for today was just identifying possible variable stars it wasn't too big of a problem. I was able to get it done and head to the beach again this evening. Our new total for variable candidates is 49. I have a feeling some can be tossed out right away for being close to the edge of the frame, but I'll probably make light curves for those anyway. It's not too hard and doesn't hurt anything.
Astronomy Internship - Day 46
Turns out that there was a good reason that star was missing from our list. It turns out that it wasn't in any list we'd produced. Apparently, Dr. Twarog's program was overzealous in its cutting of stars and trimmed our list down to around 500 when we should have had closer to 1,000.
She's fixed the problem, but it means I'm going to have to redo the calibrations for the filters to put everything on the standard system. That took me three days to do last time, but I was able to redo everything today now that I knew what I was doing.
However, it also means that we're probably going to have a bunch more stars coming up here to make light curves for. Given that we roughly doubled the number of stars, that should put our total variable candidates around 40-50. But I'll identify those tomorrow.
She's fixed the problem, but it means I'm going to have to redo the calibrations for the filters to put everything on the standard system. That took me three days to do last time, but I was able to redo everything today now that I knew what I was doing.
However, it also means that we're probably going to have a bunch more stars coming up here to make light curves for. Given that we roughly doubled the number of stars, that should put our total variable candidates around 40-50. But I'll identify those tomorrow.
Astronomy Internship - Day 45
Groggy as hell today. My sleep schedule is waaay off thanks to the con. I didn't wake up till almost 11:00 California time. And when I say "woke up" that only refers to my body. My brain stayed in that fuzzy world of half asleep-ness for the rest of the day. Thus, I wasn't terribly productive. My first task for the day was to make light curves from the 21 variable star candidates I'd picked out. However, as soon as my brain cleared enough to do this, we were kicked out of the lab because an astronomy class needed to use it.
So instead, Dr Sandquist gave a cheery little talk on the difficulties in pursuing a career in Astronomy, applying for grad school, surviving it, and then having years of post-doc before hopefully landing a perminant position somewhere. It was both terrifying yet reassuring because I have some to realize that of the 4 professors there, only one didn't have some sort of academic difficulties as an undergrad. Thus, I don't feel too discourage for my troubles.
I eventually did get the light curves made tonight. However, looking over them, none of them look like especailly good candidates based on what pieces of the light curve we have. I also noticed that our candidates don't include the variable star identified in the Crinklaw & Talbert paper. However, it looked to possibly be an eclipsing binary, so it's entirely possible we just didn't catch it at the right time.
So instead, Dr Sandquist gave a cheery little talk on the difficulties in pursuing a career in Astronomy, applying for grad school, surviving it, and then having years of post-doc before hopefully landing a perminant position somewhere. It was both terrifying yet reassuring because I have some to realize that of the 4 professors there, only one didn't have some sort of academic difficulties as an undergrad. Thus, I don't feel too discourage for my troubles.
I eventually did get the light curves made tonight. However, looking over them, none of them look like especailly good candidates based on what pieces of the light curve we have. I also noticed that our candidates don't include the variable star identified in the Crinklaw & Talbert paper. However, it looked to possibly be an eclipsing binary, so it's entirely possible we just didn't catch it at the right time.
Astronomy Intership - Day 44
Final day of Comic Con. I didn't do too much exciting today. More DDR and Pirates. I looked around to see if any of the booths were having any last minute clearances but didn't find anything. I did wind up getting all the demo materials from the Pirates booth which was a pretty sweet deal. It ended at 5:00, so I headed home and grabbed dinner.
If you want to see all the pictures (71 worth showing), go here.
If you want to see all the pictures (71 worth showing), go here.
Astronomy Internship - Day 43
Another great day at Comic Con. Today there was a "hide from the stormtroopers" game in which you could get a badge, and if a stormtrooper (or other Star Wars baddie) caught you, you had to hand it over. If you still had it at the end of the day, you would be given a raffle ticket for some pretty nice prizes drawn the next day.
So I spent most of my day at the Wizkids booth teaching kids to play Pirates and giving their reps a little bit of a break since the game has become very popular thanks to the Pirates of the Carribean movie that's just released. Poor guys couldn't keep up with all the people coming to try it out.
Most of the rest of my time was spent at the Konami booth where they had a demo of the new Dance Dance Revolution game coming out this fall. The pads they had there were pretty poor, so instead of playing for technical merits, I ended up playing freestyle the whole day (see here for a good sample of DDR freestyle).
I'd planned on going to costume masquerade tonight, but unfortunately, I got so carried away doing other things, I lost track of time and couldn't get tickets so I ended up coming home early since there wasn't any other fun night programming.
So I spent most of my day at the Wizkids booth teaching kids to play Pirates and giving their reps a little bit of a break since the game has become very popular thanks to the Pirates of the Carribean movie that's just released. Poor guys couldn't keep up with all the people coming to try it out.
Most of the rest of my time was spent at the Konami booth where they had a demo of the new Dance Dance Revolution game coming out this fall. The pads they had there were pretty poor, so instead of playing for technical merits, I ended up playing freestyle the whole day (see here for a good sample of DDR freestyle).
I'd planned on going to costume masquerade tonight, but unfortunately, I got so carried away doing other things, I lost track of time and couldn't get tickets so I ended up coming home early since there wasn't any other fun night programming.
Astronomy Internship - Day 42
My advisor was entertaining a guest back in Kansas today, so she didn't have time to prepare anything new for me and I had the day off. Back to Comic Con it was for me. I ended up doing quite a bit of shopping today. I got my girlfriend a hoodie featuring the image of Totoro from the Miazaki film "My Neighbor Totoro".
I also got signatures from Temura Morrison and David Prowse who played Jango Fett and Darth Vader, respectively, in Star Wars. Carrie Fisher (Princess Leia) was also there, but every time I walked by she was ignoring fans and talking on her cell phone. I wasn't about to pay $40 for her signature.
My other big goodie was the exclusive convention ship from the WizKids constructable strategy game Pirates. It was a very long day but very fun. Two days left!
I also got signatures from Temura Morrison and David Prowse who played Jango Fett and Darth Vader, respectively, in Star Wars. Carrie Fisher (Princess Leia) was also there, but every time I walked by she was ignoring fans and talking on her cell phone. I wasn't about to pay $40 for her signature.
My other big goodie was the exclusive convention ship from the WizKids constructable strategy game Pirates. It was a very long day but very fun. Two days left!
Wednesday, July 26, 2006
3d. Radial Velocity
As we’ve seen in previous posts, light is able to give many wonderful pieces of information such as temperature, color, brightness, age, and chemical composition. But now we’ll explore how light is able to give us a property known as radial velocity.
First off, what is radial velocity? In short, it’s the speed of an object towards or away from the observer. Whether or not you realize it, you’re already familiar with a very common use of this: Doppler radar. This device uses radar pulses which are reflected by water vapor and then their speed, towards or away from the detector, is measured.
But how?
The answer is actually right in front of your eyes. It’s due to something known as the Doppler effect. It sounds pretty exotic but again, it’s something you’re most certainly familiar with. If you’ve ever listened to a train passing as it blows its whistle, you’ve heard the Doppler effect. As the train approaches you, the pitch of the whistle seems higher but drops off as it speeds past. If you can’t picture what I’m talking about try here.
So now that we know what the Doppler effect is, what causes it? You’re probably well aware the sound is actually a wave. We’ve already had a good look at what waves are and how they’re characterized for light, so we’ll apply some of the same concepts here before moving on.
With sound, the pitch of something like a train whistle depends on the distance between successive waves, called the wavelength. If you have a long wavelength, this would be a low pitch sound. If there’s a short wavelength, this is a high pitch.
A train whistle has a single tone, so the distance between waves should be constant which means a constant pitch. If you stand by a train that’s holding still as it blows its whistle, you’ll realize this is true.
But let’s imagine that the train is now moving towards you. The crest of one wave is emitted. In the time before the next one is emitted, the train moves towards you, catching up a bit to the wave it just gave off. Thus, when it gives off the next one, it will be closer to the previous one than if the train was remaining stationary. This gives the sound that you’d hear a shorter wavelength, and thus, a higher pitch.
The opposite is true if the train is moving away from you. Since the train is moving the opposite direction of the wave that you’re hearing, each successive wave takes longer to reach you, meaning a longer wavelength, and therefore, a lower pitch.
Here’s a nice image to sum that all up:
Source
So how does that have anything to do with light?
Conveniently enough, light is also a wave and the same rules apply. If an object that’s giving off light is moving towards you, the wavelength gets shortened. With light, this means that it looks bluer. If it moves away, the opposite is true and it looks redder.
But how do we tell if that observed color is due to the actual color of the star, or if it’s due to some sort of shift? To figure this out, we’ll need a reference point that we know what the wavelength should be.
Fortunately, this isn’t too hard. In my last post concerning spectroscopy, we explored types of spectra called absorption spectra in which dark lines were taken out. These lines were due to transitions of the electrons in atoms. Since these transitions have a fixed energy, that means they have a fixed wavelength.
Unless something happens to shift that wavelength that is.
The easiest absorption lines to find generally are two prominent ones due to hydrogen, known as the HĪ± and the HĆ lines. When the source is at rest with respect to the observer (neither moving towards or away) these lines appear at 656.3 nm and 486.5 nm respectively.
So since we know where these lines should be, we can compare them to where they are. The further they’re shifted, the faster the object is moving towards or away from us. If they’re shifted to the blue, it’s moving towards us. If it’s shifted towards the red, it’s moving away.
With this, we’ve examined many of the important tools that astronomers frequently use. With these tools, we can generate a huge number of facts about our universe. However facts are actually pretty useless in science. It’s what those facts mean that is important. To get this meaning, we have to tie facts together with something that is actually useful: a theory.
Thus, in my next series of posts on this topic, I’ll show you a few ways these tools are put to use to make some of the conclusions (read: theories) that are both fundamental and exciting to astronomy.
First off, what is radial velocity? In short, it’s the speed of an object towards or away from the observer. Whether or not you realize it, you’re already familiar with a very common use of this: Doppler radar. This device uses radar pulses which are reflected by water vapor and then their speed, towards or away from the detector, is measured.
But how?
The answer is actually right in front of your eyes. It’s due to something known as the Doppler effect. It sounds pretty exotic but again, it’s something you’re most certainly familiar with. If you’ve ever listened to a train passing as it blows its whistle, you’ve heard the Doppler effect. As the train approaches you, the pitch of the whistle seems higher but drops off as it speeds past. If you can’t picture what I’m talking about try here.
So now that we know what the Doppler effect is, what causes it? You’re probably well aware the sound is actually a wave. We’ve already had a good look at what waves are and how they’re characterized for light, so we’ll apply some of the same concepts here before moving on.
With sound, the pitch of something like a train whistle depends on the distance between successive waves, called the wavelength. If you have a long wavelength, this would be a low pitch sound. If there’s a short wavelength, this is a high pitch.
A train whistle has a single tone, so the distance between waves should be constant which means a constant pitch. If you stand by a train that’s holding still as it blows its whistle, you’ll realize this is true.
But let’s imagine that the train is now moving towards you. The crest of one wave is emitted. In the time before the next one is emitted, the train moves towards you, catching up a bit to the wave it just gave off. Thus, when it gives off the next one, it will be closer to the previous one than if the train was remaining stationary. This gives the sound that you’d hear a shorter wavelength, and thus, a higher pitch.
The opposite is true if the train is moving away from you. Since the train is moving the opposite direction of the wave that you’re hearing, each successive wave takes longer to reach you, meaning a longer wavelength, and therefore, a lower pitch.
Here’s a nice image to sum that all up:
Source
So how does that have anything to do with light?
Conveniently enough, light is also a wave and the same rules apply. If an object that’s giving off light is moving towards you, the wavelength gets shortened. With light, this means that it looks bluer. If it moves away, the opposite is true and it looks redder.
But how do we tell if that observed color is due to the actual color of the star, or if it’s due to some sort of shift? To figure this out, we’ll need a reference point that we know what the wavelength should be.
Fortunately, this isn’t too hard. In my last post concerning spectroscopy, we explored types of spectra called absorption spectra in which dark lines were taken out. These lines were due to transitions of the electrons in atoms. Since these transitions have a fixed energy, that means they have a fixed wavelength.
Unless something happens to shift that wavelength that is.
The easiest absorption lines to find generally are two prominent ones due to hydrogen, known as the HĪ± and the HĆ lines. When the source is at rest with respect to the observer (neither moving towards or away) these lines appear at 656.3 nm and 486.5 nm respectively.
So since we know where these lines should be, we can compare them to where they are. The further they’re shifted, the faster the object is moving towards or away from us. If they’re shifted to the blue, it’s moving towards us. If it’s shifted towards the red, it’s moving away.
With this, we’ve examined many of the important tools that astronomers frequently use. With these tools, we can generate a huge number of facts about our universe. However facts are actually pretty useless in science. It’s what those facts mean that is important. To get this meaning, we have to tie facts together with something that is actually useful: a theory.
Thus, in my next series of posts on this topic, I’ll show you a few ways these tools are put to use to make some of the conclusions (read: theories) that are both fundamental and exciting to astronomy.
Monday, July 24, 2006
Sin against nature?
In Terry Pratchet's novel, Monstrous Regmient, Pratchet discribes his fictional country in which the God, Nuggan, has died but echoes remain, handing down new abominations to the priests. But these abominations keep getting more and more senseless, oysters, rocks, and the color blue (thus devout Nugganites avoid looking at the sky).
But sometimes truth is stranger than fiction. Earlier I posted Brother Jed's 10 commandments, the majority of which were senseless. But it's easy to brush Brother Jed off as a bit deranged.
However, it's another thing when a major church does it. We can understand the biblical 10 commandments as being pretty solid but perhaps no so solid is the insistance that birth control is a no-no to some religious sects, as is the restriction of gay marriage based on a single sentence from the bible. But it seems that God's given a notice to bishop Richard Chartres of the Church of England saying that taking planes for holiday travel is "a sin" against nature. I'm all for cutting down on pollution, and support the idea of this, but it sounds to me that bishop Chartres is taking this a little too far. Perhaps he forgot that commandment about not worshiping false idols (like nature).
But sometimes truth is stranger than fiction. Earlier I posted Brother Jed's 10 commandments, the majority of which were senseless. But it's easy to brush Brother Jed off as a bit deranged.
However, it's another thing when a major church does it. We can understand the biblical 10 commandments as being pretty solid but perhaps no so solid is the insistance that birth control is a no-no to some religious sects, as is the restriction of gay marriage based on a single sentence from the bible. But it seems that God's given a notice to bishop Richard Chartres of the Church of England saying that taking planes for holiday travel is "a sin" against nature. I'm all for cutting down on pollution, and support the idea of this, but it sounds to me that bishop Chartres is taking this a little too far. Perhaps he forgot that commandment about not worshiping false idols (like nature).
Saturday, July 22, 2006
Astronomy Internship - Day 41
I was actually pretty productive today. We've gotten our reddening estimate from the IR data as well as a preliminary distance modulus that agrees moderately well with values in the literature. There's still more work to do on accounting for various things, but we're coming along. The next step will be to use this information to give us insight into the UBVI data we'd previously gathered to help refine that, which is were our ultimate final answers will come from.
After work I headed off to Comic Con for day 1 of 4. It was a blast. The big event I hit tonight was the Star Wars Fan Film awards. I used to be fairly active on theforce.net's fan film message boards on which I virtually "met" several of the people winning awards and thus, got some priority in seating (was one of the first hundred in out of 3,000-4,000) and then got to chat with everyone afterwards. Among them was Steve Sansweet, the head of fan relations for Lucasfilm:
The highlight of the ceremony was the world premiere of the long anticipated "Return of Pink 5: Volume 2". The Pink 5 series has been a fan favourite for a few years now (See the original here, as well as Pink 5 Strikes Back and Return of Pink 5: Vol 1 here)
Unfortunately for everyone except those lucky few thousand, Volume 2 isn't going to be released for another few months. However, I also got to meet the lead actress, Amy Earhart.
Thus, I have secured bragging rights in nerd circles for years to come. The whole thing was a huge blast and a ton of laughs. I encourage anyone interested and needs a few laughs to get away from the oppressing insanity of the anti-science crowd to check out all the winners, as well as all the other entries here.
I'll be going back tomorrow for a lot more fun since my advisor gave me the day off to figure out exactly how we want to proceed from here.
After work I headed off to Comic Con for day 1 of 4. It was a blast. The big event I hit tonight was the Star Wars Fan Film awards. I used to be fairly active on theforce.net's fan film message boards on which I virtually "met" several of the people winning awards and thus, got some priority in seating (was one of the first hundred in out of 3,000-4,000) and then got to chat with everyone afterwards. Among them was Steve Sansweet, the head of fan relations for Lucasfilm:
The highlight of the ceremony was the world premiere of the long anticipated "Return of Pink 5: Volume 2". The Pink 5 series has been a fan favourite for a few years now (See the original here, as well as Pink 5 Strikes Back and Return of Pink 5: Vol 1 here)
Unfortunately for everyone except those lucky few thousand, Volume 2 isn't going to be released for another few months. However, I also got to meet the lead actress, Amy Earhart.
Thus, I have secured bragging rights in nerd circles for years to come. The whole thing was a huge blast and a ton of laughs. I encourage anyone interested and needs a few laughs to get away from the oppressing insanity of the anti-science crowd to check out all the winners, as well as all the other entries here.
I'll be going back tomorrow for a lot more fun since my advisor gave me the day off to figure out exactly how we want to proceed from here.
Thursday, July 20, 2006
Patterns from the.... Alligator?
Last week, I took a look at the way people seem to find patterns in the strangest of places. Perhaps a bit off cue, but God is now wanting to appear in Florida. On an alligator of all places.
Perhaps I just can't see the holiness, but I don't see GOD written anywhere on there. What do I see?
G U Ī
But don't let that stop you from using your imagination to validate your mythology.
Perhaps I just can't see the holiness, but I don't see GOD written anywhere on there. What do I see?
G U Ī
But don't let that stop you from using your imagination to validate your mythology.
Wednesday, July 19, 2006
Astronomy Internship - Day 40
Wow... 40 days already. Just a little over 3 weeks left in this internship.
I ended up being relatively productive today. I finally caught up on my sleep. It hasn't fixed all my problems (headache, dizziness, etc...), but at least I'm not feeling like I'm about to pass out all the time.
When I got to the lab today, I called my instructor back at KU and finally got a good grasp on where were going from here. What I hadn't caught from the paper I was given was that the key feature we're looking for is the "Red Giant Clump". This feature has a very distinct absolute magnitude (ie, a brightness from a specified distance of 10 pc) and a known color (temperature).
Thus, if we can identify this on our HR diagrams, we'll be able to (presumably) figure out what the distance is to the cluster as well as how much interference there is thanks to the dust. So today, I went through about 30 stars looking to make sure they were all actually the same color, and then we compared a few of their radial velocities to make sure that they were actually all in the cluster and not stars that are just in the same field of view.
So now we have to take those stars and use them to get the distance and redenning and we'll be moving right along.
I don't know how much I'll be blogging the next few days (not that I've been blogging much since I've been ill). I'm going to be headed to Comic Con here in San Diego in my free time starting tomorrow through Sunday.
I ended up being relatively productive today. I finally caught up on my sleep. It hasn't fixed all my problems (headache, dizziness, etc...), but at least I'm not feeling like I'm about to pass out all the time.
When I got to the lab today, I called my instructor back at KU and finally got a good grasp on where were going from here. What I hadn't caught from the paper I was given was that the key feature we're looking for is the "Red Giant Clump". This feature has a very distinct absolute magnitude (ie, a brightness from a specified distance of 10 pc) and a known color (temperature).
Thus, if we can identify this on our HR diagrams, we'll be able to (presumably) figure out what the distance is to the cluster as well as how much interference there is thanks to the dust. So today, I went through about 30 stars looking to make sure they were all actually the same color, and then we compared a few of their radial velocities to make sure that they were actually all in the cluster and not stars that are just in the same field of view.
So now we have to take those stars and use them to get the distance and redenning and we'll be moving right along.
I don't know how much I'll be blogging the next few days (not that I've been blogging much since I've been ill). I'm going to be headed to Comic Con here in San Diego in my free time starting tomorrow through Sunday.
Astronomy Internship - Day 39
Dr. Twarog is still working on taking a closer look at the variable candidates. I think we've been able to pick out the red giant clump now, all 2-3 stars in it...
What we're trying to do is isolate the red giant stars because it's been demonstrated that the slope of that branch is directly related to the metallicity of a star (ie, the amount of material heavier than helium).
I've also put together a few other HR diagrams from the data using different color indicies to see if that would help anything stand out. It seems that the J, J-K diagram works best but only marginally.
I haven't been getting much done because I've been pretty off in my sleep schedule for some reason. The past two nights I've woken up at 6am shaking and with very strange dreams that start as soon as I try to get back to sleep so I never really get back into a restful stage of sleep. Thus, I'm very far off on sleep right now.
What we're trying to do is isolate the red giant stars because it's been demonstrated that the slope of that branch is directly related to the metallicity of a star (ie, the amount of material heavier than helium).
I've also put together a few other HR diagrams from the data using different color indicies to see if that would help anything stand out. It seems that the J, J-K diagram works best but only marginally.
I haven't been getting much done because I've been pretty off in my sleep schedule for some reason. The past two nights I've woken up at 6am shaking and with very strange dreams that start as soon as I try to get back to sleep so I never really get back into a restful stage of sleep. Thus, I'm very far off on sleep right now.
Astronomy Internship - Day 38
Things are moving pretty slowly now. I've put together HR diagrams from the 2MASS data now, but they're very sketchy. The turnoff point is fairly clearly defined, but the main sequence continues on past it which is confusing. The red giant branch is also pretty wide which makes things harder. I'm also supposed to be finding the red giant clump, but it's not sticking out at all.
I did end up going through the list of all the stars and pull out about 20 that are good candidates for variable stars and have sent those on to Dr. Twarog to take a closer look at. Seven or eight of them probably had large errors due to being close to the edge of the frame where the CCD sensitivity isn't always consistent. But aside from that, there's a good possibility that we'll be adding to the number of known variable stars in NGC 7142 (currently 1).
I did end up going through the list of all the stars and pull out about 20 that are good candidates for variable stars and have sent those on to Dr. Twarog to take a closer look at. Seven or eight of them probably had large errors due to being close to the edge of the frame where the CCD sensitivity isn't always consistent. But aside from that, there's a good possibility that we'll be adding to the number of known variable stars in NGC 7142 (currently 1).
Astronomy Internship - Day 38
Things are moving pretty slowly now. I've put together HR diagrams from the 2MASS data now, but they're very sketchy. The turnoff point is fairly clearly defined, but the main sequence continues on past it which is confusing. The red giant branch is also pretty wide which makes things harder. I'm also supposed to be finding the red giant clump, but it's not sticking out at all.
I did end up going through the list of all the stars and pull out about 20 that are good candidates for variable stars and have sent those on to Dr. Twarog to take a closer look at. Seven or eight of them probably had large errors due to being close to the edge of the frame where the CCD sensitivity isn't always consistent. But aside from that, there's a good possibility that we'll be adding to the number of known variable stars in NGC 7142 (currently 1).
I did end up going through the list of all the stars and pull out about 20 that are good candidates for variable stars and have sent those on to Dr. Twarog to take a closer look at. Seven or eight of them probably had large errors due to being close to the edge of the frame where the CCD sensitivity isn't always consistent. But aside from that, there's a good possibility that we'll be adding to the number of known variable stars in NGC 7142 (currently 1).
Monday, July 17, 2006
Astronomy Internship - Day 37
I did absolutely nothing productive today.
I spent the entire day on my computer at the gaia online forums defending the big bang and taking a 400 question survey.
It was wonderful.
I spent the entire day on my computer at the gaia online forums defending the big bang and taking a 400 question survey.
It was wonderful.
Astronomy Internship - Day 36
Somehow I think I managed to spend the majority of my day trying to figure out how to spend my day. I've been wanting to get my haircut, but it doesn't seem there's any location close by. I then tried to figure out what to do for lunch and finally decided to get pizza. I knew I didn't want chain pizza so I spent an hour playing on Google trying to find a smaller place within walking distance.
I ended up finding a pretty good one only a few miles away. More sausage and artichoke pizza. Mmmmm.
From there, I worked on the Astronomical Data post and played on some internet forums the rest of the day.
I ended up finding a pretty good one only a few miles away. More sausage and artichoke pizza. Mmmmm.
From there, I worked on the Astronomical Data post and played on some internet forums the rest of the day.
Saturday, July 15, 2006
Astronomical Data – 3c. Spectroscopy
In today’s post, we’ll be exploring another astronomical technique known as spectroscopy in which astronomers can use light to determine chemical composition.
If you’ve forgotten where light comes from, you might want to go back and reread my earlier post on where light comes from since we’ll be referring back to that quite a bit in this post. Assuming you do remember, let’s take an expanded look at all that.
You should recall that we can get the entire continuous spectrum of light (ie, the entire rainbow including what lies beyond just the visible part) due to electrons falling into orbitals from outside the atom. Since they can fall any distance, that’s what makes it possible to have every wavelength thus making the spectrum complete.
However, in this scenario I made a few assumptions that you may or may not have caught.
The first is that there are slots for the electrons to fall into. If the electron is already neutral (ie, has as many electrons as there are protons in the nucleus) then the atom won’t readily accept any more.
The second is that, if an atom is needing an electron to become neutral, that there’s actually some nearby to fall in.
On the surface of stars, this isn’t a bad assumption. The heat causes atoms to become ionized (lose their electrons) and since the star is relatively dense, those electrons are right nearby to fall into another atom, give off a photon, and then get ionized again.
But in case you haven’t noticed, stars aren’t the only thing in the galaxy. So, as you might be anticipating, continuous spectrums aren’t the only kind.
Let’s consider another case in which we have a low density gas that’s warm but not warm enough to actually ionize the atom (for the time being, stick with the hydrogen model in your mind since it’s easiest). In this, since the atom will be imparted with some energy, but not enough to ionize it, the electrons will jump up orbitals and fall back down, emitting a photon.
But since, as I discussed in the previous post, the orbitals have discreet energies, the photons emitted will be confined to those energies as well, and thus, only certain wavelengths. So for hydrogen, here’s what that looks like in the visible part of the spectrum:
Since hydrogen is the most plentiful element in the universe, we see this pattern popping up almost everywhere. However, what happens if we have other gasses in the same condition?
In that case, we get different lines being emitted due to different atomic configuration. Here’s a few more:
As you can see each element has a unique configuration of lines. I generally compare this to a barcode that’s unique to each different element. Thus, if astronomers can put the light from one of these low density, warm clouds through a spectrum and see a pattern that conforms to one of these, they’ll know what element is present. This isn’t always as easy as it sounds for many reasons. One of the major reasons is that there’s frequently more than one element present in what we’re wanting to look at, so sorting things out can get difficult. Another (which we’ll explore later) is that such lines aren’t always where they’re supposed to be due to a few different reasons.
But assuming that things can be sorted out, an accurate determination of chemical makeup can be determined! This type of spectra, one with distinct lines, is called an emission spectra.
So keeping all that in mind, let’s take a look at another scenario.
In this one, let’s allow the cloud of gas to be nice and cold heat isn’t causing any electrons to jump up into higher orbitals. In this case, density is unimportant since the atoms already have their lower energy levels filled and aren’t accepting electrons.
But now let’s imagine that we put a source that emits a continuous spectrum behind it so this cloud is in the way. In this scenario, light from the continuous spectrum source will have to pass through the cold cloud. Here’s where something special happens.
If a photon happens hit an atom of the cold gas, it can get absorbed. But only if it’s of one of the specific energies that corresponds to one of those jumps between orbitals. If that happens, and the photon is absorbed, then the electron will take that energy and hop up.
Of course, since that’s a higher energy level, it will fall back down, emitting a photon of the exact same energy as the one it absorbed.
So what? Photon absorbed and given right back off. What’s the big deal?
The trick here is that, the photon that is given off can be given off in any direction. The chance that it will happen to go straight towards the observer is pretty slim. Thus, the observer no longer sees light at the wavelength that corresponds to that energy!
So now instead of having a continuous spectrum, the observer will see one that has lines subtracted from it at the same wavelengths that the gas the light was passing through would emit if it were hot.
Where do we see this? The major place is in stars.
Yeah yeah, I know I said stars have continuous spectrums earlier. And they would. If it weren’t for the fact that they don’t have solid surfaces and just slowly fade into a sort of extended atmosphere. That atmosphere is (relatively) cool, and thus, will absorb pieces of the continuous spectrum generated lower in the star.
So what’s this called? As you might expect, it’s called an absorption spectra.
Let’s take a look at one.
Want to take a guess what star this is?
It’s the Sun! And wow is that a lot of absorption lines! Some of the most prominent ones are caused by hydrogen and helium. Some of the other, fainter ones are caused by trace gasses in the Sun’s atmosphere, but most are caused by our own atmosphere.
As a brief aside, you’ll also notice that the spectrum is brightest in that yellow green area as I pointed out in a few other posts.
Incidentally, the late mid 1800’s was the first time the solar spectrum was examined. At that time, astronomers first determined that the sun was made mostly of hydrogen and were able to pick out many other elements. However, some prominent lines couldn’t be explained. Thus, the presence of a yet undiscovered element was inferred. This element was named Helium after the Greek word for sun, Helios. Helium was later discovered on Earth.
So let’s do some recapping before we go any further:
We’ve now looked at three types of spectra: continuous, emission, and absorption.
With a continuous spectrum or absorption spectra, we’ll be able to find the wavelength where the most light is given off (as I pointed out in my last post), which can give us the temperature of the star.
Emission spectra and absorption spectra are useful because the pattern of lines tell us what chemicals are present.
Continuous spectra come from hot, high density gasses.
Emission spectra come from low density, warm gas.
Absorption spectra come from continuous spectra passing through cool gas.
But the fun doesn’t end there!
Let’s take another look at that absorption spectra. But this time, let’s do it in a graphical form:
The blue line here is what the continuous spectrum would look like for this star if there weren’t the deep absorption lines present. Those very deep ones at ~430, ~480, ~520, and ~655 nm are those caused by hydrogen we looked at earlier.
You’ll notice they’re pretty damned deep. However, the other ones aren’t so deep. The reason has to do with the abundance of each element in that star’s atmosphere. Since there’s a lot of hydrogen in stars, it makes sense that the hydrogen lines be the deepest.
So by looking at how deep each line is astronomers can figure out the ratio of elements which is a pretty nifty trick.
These absorption lines can also be used in other ways. Another use is that they reveal the presence of magnetic fields thanks to an effect known as the Zeeman effect which causes the spectral lines to split into two if there’s a magnetic field present.
If you recall the solar telescope at Mt. Wilson I talked about, it looks for this spectral line splitting at thousands of different points on the face of the sun, which allows the astronomers working on that project to essentially map the magnetic field.
So that’s it for this post. In my next post, we’ll look at some other uses of these lines to determine other quantities, but since it will require another bout of background explanation, I’ll save that for the next post.
If you’ve forgotten where light comes from, you might want to go back and reread my earlier post on where light comes from since we’ll be referring back to that quite a bit in this post. Assuming you do remember, let’s take an expanded look at all that.
You should recall that we can get the entire continuous spectrum of light (ie, the entire rainbow including what lies beyond just the visible part) due to electrons falling into orbitals from outside the atom. Since they can fall any distance, that’s what makes it possible to have every wavelength thus making the spectrum complete.
However, in this scenario I made a few assumptions that you may or may not have caught.
The first is that there are slots for the electrons to fall into. If the electron is already neutral (ie, has as many electrons as there are protons in the nucleus) then the atom won’t readily accept any more.
The second is that, if an atom is needing an electron to become neutral, that there’s actually some nearby to fall in.
On the surface of stars, this isn’t a bad assumption. The heat causes atoms to become ionized (lose their electrons) and since the star is relatively dense, those electrons are right nearby to fall into another atom, give off a photon, and then get ionized again.
But in case you haven’t noticed, stars aren’t the only thing in the galaxy. So, as you might be anticipating, continuous spectrums aren’t the only kind.
Let’s consider another case in which we have a low density gas that’s warm but not warm enough to actually ionize the atom (for the time being, stick with the hydrogen model in your mind since it’s easiest). In this, since the atom will be imparted with some energy, but not enough to ionize it, the electrons will jump up orbitals and fall back down, emitting a photon.
But since, as I discussed in the previous post, the orbitals have discreet energies, the photons emitted will be confined to those energies as well, and thus, only certain wavelengths. So for hydrogen, here’s what that looks like in the visible part of the spectrum:
Since hydrogen is the most plentiful element in the universe, we see this pattern popping up almost everywhere. However, what happens if we have other gasses in the same condition?
In that case, we get different lines being emitted due to different atomic configuration. Here’s a few more:
As you can see each element has a unique configuration of lines. I generally compare this to a barcode that’s unique to each different element. Thus, if astronomers can put the light from one of these low density, warm clouds through a spectrum and see a pattern that conforms to one of these, they’ll know what element is present. This isn’t always as easy as it sounds for many reasons. One of the major reasons is that there’s frequently more than one element present in what we’re wanting to look at, so sorting things out can get difficult. Another (which we’ll explore later) is that such lines aren’t always where they’re supposed to be due to a few different reasons.
But assuming that things can be sorted out, an accurate determination of chemical makeup can be determined! This type of spectra, one with distinct lines, is called an emission spectra.
So keeping all that in mind, let’s take a look at another scenario.
In this one, let’s allow the cloud of gas to be nice and cold heat isn’t causing any electrons to jump up into higher orbitals. In this case, density is unimportant since the atoms already have their lower energy levels filled and aren’t accepting electrons.
But now let’s imagine that we put a source that emits a continuous spectrum behind it so this cloud is in the way. In this scenario, light from the continuous spectrum source will have to pass through the cold cloud. Here’s where something special happens.
If a photon happens hit an atom of the cold gas, it can get absorbed. But only if it’s of one of the specific energies that corresponds to one of those jumps between orbitals. If that happens, and the photon is absorbed, then the electron will take that energy and hop up.
Of course, since that’s a higher energy level, it will fall back down, emitting a photon of the exact same energy as the one it absorbed.
So what? Photon absorbed and given right back off. What’s the big deal?
The trick here is that, the photon that is given off can be given off in any direction. The chance that it will happen to go straight towards the observer is pretty slim. Thus, the observer no longer sees light at the wavelength that corresponds to that energy!
So now instead of having a continuous spectrum, the observer will see one that has lines subtracted from it at the same wavelengths that the gas the light was passing through would emit if it were hot.
Where do we see this? The major place is in stars.
Yeah yeah, I know I said stars have continuous spectrums earlier. And they would. If it weren’t for the fact that they don’t have solid surfaces and just slowly fade into a sort of extended atmosphere. That atmosphere is (relatively) cool, and thus, will absorb pieces of the continuous spectrum generated lower in the star.
So what’s this called? As you might expect, it’s called an absorption spectra.
Let’s take a look at one.
Want to take a guess what star this is?
It’s the Sun! And wow is that a lot of absorption lines! Some of the most prominent ones are caused by hydrogen and helium. Some of the other, fainter ones are caused by trace gasses in the Sun’s atmosphere, but most are caused by our own atmosphere.
As a brief aside, you’ll also notice that the spectrum is brightest in that yellow green area as I pointed out in a few other posts.
Incidentally, the late mid 1800’s was the first time the solar spectrum was examined. At that time, astronomers first determined that the sun was made mostly of hydrogen and were able to pick out many other elements. However, some prominent lines couldn’t be explained. Thus, the presence of a yet undiscovered element was inferred. This element was named Helium after the Greek word for sun, Helios. Helium was later discovered on Earth.
So let’s do some recapping before we go any further:
We’ve now looked at three types of spectra: continuous, emission, and absorption.
With a continuous spectrum or absorption spectra, we’ll be able to find the wavelength where the most light is given off (as I pointed out in my last post), which can give us the temperature of the star.
Emission spectra and absorption spectra are useful because the pattern of lines tell us what chemicals are present.
Continuous spectra come from hot, high density gasses.
Emission spectra come from low density, warm gas.
Absorption spectra come from continuous spectra passing through cool gas.
But the fun doesn’t end there!
Let’s take another look at that absorption spectra. But this time, let’s do it in a graphical form:
The blue line here is what the continuous spectrum would look like for this star if there weren’t the deep absorption lines present. Those very deep ones at ~430, ~480, ~520, and ~655 nm are those caused by hydrogen we looked at earlier.
You’ll notice they’re pretty damned deep. However, the other ones aren’t so deep. The reason has to do with the abundance of each element in that star’s atmosphere. Since there’s a lot of hydrogen in stars, it makes sense that the hydrogen lines be the deepest.
So by looking at how deep each line is astronomers can figure out the ratio of elements which is a pretty nifty trick.
These absorption lines can also be used in other ways. Another use is that they reveal the presence of magnetic fields thanks to an effect known as the Zeeman effect which causes the spectral lines to split into two if there’s a magnetic field present.
If you recall the solar telescope at Mt. Wilson I talked about, it looks for this spectral line splitting at thousands of different points on the face of the sun, which allows the astronomers working on that project to essentially map the magnetic field.
So that’s it for this post. In my next post, we’ll look at some other uses of these lines to determine other quantities, but since it will require another bout of background explanation, I’ll save that for the next post.
Astronomical Data 3b. – Main sequence turnoff
In my last Astronomical Data post, I discussed a wonderfully important tool in astronomy known as the HR diagram. We saw how it gave a wonderful relationship between temperature (or color, or mass) and the luminosity of the star. Additionally, it could also help determine the radius of a star.
So all in all, it’s a pretty nifty little tool. But at the end of my post, I pointed out that, if a HR diagram was composed for a cluster instead of for a number of random, unrelated stars, it gave could also give us the age!
To explain this, I’ll start off by giving away the underlying reason: Massive stars evolve faster. This runs a bit counter to what one might expect.
Most people are aware that stars convert hydrogen to helium in their cores. So you’d expect with more massive stars, there should be a lot more hydrogen to have to use up and those little bitty red stars down in the bottom right hand corner of the HR diagram should burn out pretty quickly.
However, the opposite is actually true. Massive stars are the rock legends of astronomy: live fast, die young, and go out in a blaze. Meanwhile, their diminutive little brothers will putter along for billions of years.
So what causes massive stars to die out so quickly?
The reason is that fusion occurs more rapidly at higher temperatures and at higher densities. Massive stars have both of these quantities in excess. Their mass squeezes the core to immense pressures and temperatures.
If you think about it, this should make sense now. If fusion is caused by two hydrogen nuclei ramming into one another fast enough to stick (ie, fuse) then there’s going to be a hell of a lot more collisions in a tightly packed stellar nuclei. Additionally, when it’s really hot, atoms bounce around a lot more and with greater momentum.
Taking these two together, it’s not a huge challenge to see why massive stars burn their fuel and die faster.
But what does that have to do with the HR diagram?
If you remember in the last post, I pointed out that very special place called the “main sequence” on which stars spend the vast majority of their life. As stars begin to exhaust their fuel, they swell up and become giants.
So take a look at that HR diagram I posted before and see exactly what’s going on here. We can see the main sequence running from the upper left to the lower right across the diagram. The giants appear in the upper right. As the star swells up, it moves across the diagram heading up and to the right.
But remember that more massive stars do this before less massive ones.
Keep that in mind for a minute, as we’ll come back to it. For now, we need to discuss the other half of the situation: the cluster.
Clusters are very special little things. They’re accumulations of stars that are all gravitationally bound. They’re like a mini galaxy in a way. However, they have some very special properties which is what makes them special: They all formed from the same cloud at the same time.
That means for all intents and purposes, the stars will all be the same except for one property: Their mass.
When a cluster forms, there will be some of those massive stars we discussed earlier, and some medium ones, and some runts of the litter. Thus, if it’s a nice young cluster, all stars should be on the main sequence but scattered along the whole thing.
But give that cluster a million years and things start happening. Those giant massive stars will expend all their fuel and start drifting off the main sequence. But remember where massive stars are on the HR diagram? They’re to the upper left.
What this means is that, as stars swell up to giants, it will start at the upper left of the main sequence and slowly work its way down to the less massive stars.
Thus, by seeing where stars are turning off the main sequence, we can determine age!
This method is commonly referred to as “main sequence turnoff” and is one of the few indicators of age available in astronomy. It’s certainly the most reliable.
At this point, I’m thinking spectroscopy sounds like a very good next topic. There’s a number of other topics I’d like to discuss and don’t technically require an understanding of spectroscopy, but since spectroscopy predates many of them, I think it will help put things in a historical context which can be a good thing.
So all in all, it’s a pretty nifty little tool. But at the end of my post, I pointed out that, if a HR diagram was composed for a cluster instead of for a number of random, unrelated stars, it gave could also give us the age!
To explain this, I’ll start off by giving away the underlying reason: Massive stars evolve faster. This runs a bit counter to what one might expect.
Most people are aware that stars convert hydrogen to helium in their cores. So you’d expect with more massive stars, there should be a lot more hydrogen to have to use up and those little bitty red stars down in the bottom right hand corner of the HR diagram should burn out pretty quickly.
However, the opposite is actually true. Massive stars are the rock legends of astronomy: live fast, die young, and go out in a blaze. Meanwhile, their diminutive little brothers will putter along for billions of years.
So what causes massive stars to die out so quickly?
The reason is that fusion occurs more rapidly at higher temperatures and at higher densities. Massive stars have both of these quantities in excess. Their mass squeezes the core to immense pressures and temperatures.
If you think about it, this should make sense now. If fusion is caused by two hydrogen nuclei ramming into one another fast enough to stick (ie, fuse) then there’s going to be a hell of a lot more collisions in a tightly packed stellar nuclei. Additionally, when it’s really hot, atoms bounce around a lot more and with greater momentum.
Taking these two together, it’s not a huge challenge to see why massive stars burn their fuel and die faster.
But what does that have to do with the HR diagram?
If you remember in the last post, I pointed out that very special place called the “main sequence” on which stars spend the vast majority of their life. As stars begin to exhaust their fuel, they swell up and become giants.
So take a look at that HR diagram I posted before and see exactly what’s going on here. We can see the main sequence running from the upper left to the lower right across the diagram. The giants appear in the upper right. As the star swells up, it moves across the diagram heading up and to the right.
But remember that more massive stars do this before less massive ones.
Keep that in mind for a minute, as we’ll come back to it. For now, we need to discuss the other half of the situation: the cluster.
Clusters are very special little things. They’re accumulations of stars that are all gravitationally bound. They’re like a mini galaxy in a way. However, they have some very special properties which is what makes them special: They all formed from the same cloud at the same time.
That means for all intents and purposes, the stars will all be the same except for one property: Their mass.
When a cluster forms, there will be some of those massive stars we discussed earlier, and some medium ones, and some runts of the litter. Thus, if it’s a nice young cluster, all stars should be on the main sequence but scattered along the whole thing.
But give that cluster a million years and things start happening. Those giant massive stars will expend all their fuel and start drifting off the main sequence. But remember where massive stars are on the HR diagram? They’re to the upper left.
What this means is that, as stars swell up to giants, it will start at the upper left of the main sequence and slowly work its way down to the less massive stars.
Thus, by seeing where stars are turning off the main sequence, we can determine age!
This method is commonly referred to as “main sequence turnoff” and is one of the few indicators of age available in astronomy. It’s certainly the most reliable.
At this point, I’m thinking spectroscopy sounds like a very good next topic. There’s a number of other topics I’d like to discuss and don’t technically require an understanding of spectroscopy, but since spectroscopy predates many of them, I think it will help put things in a historical context which can be a good thing.
Friday, July 14, 2006
Astronomy Internship - Day 35
SCIENCE AT LAST!
After finally going through all of the tedious photometry, my advisor has sent me some of the preliminary results. One of the things that we're looking to do, is create a color-magnitude diagram (CMD), essentially an HR Diagram, for NGC 7142. Last night, she put together one from the first round of subtraction (before I went back and with the second routine to get the remaining stars).
So here's an inside look at what's going on! First off, the CMD:
Sketched in here, is the main sequence (yellow) and the red giant branch (red). Keep in mind that this is still a very rough piece because there's still a good amount of calibration to be going through. The cluster will need to be dereddened (ie, the effects of the interstellar cloud accounted for and subtracted) which should help a lot of the scatter along the main sequence.
Additionally, this is instrumental magnitude, meaning how bright it appeared to our instruments. But since each instrument is different, it will eventually have to be brought to a standard system. That's another adventure to look forward to.
Both of these corrections (as well as possible others) will help make things look much prettier.
But that's not all I got today! I also got a plot of the error vs the instrumental magnitude in the V filter:
You'll notice there's a definate trend here in which the uncertainty goes up significantly the fainter the star is (fainter --> higher magnitude number --> further right).
But you'll notice there's a good number of stars on there in the bluish area I put in, that don't really fall on this trend. There's several reasons for this. One is that those stars could have been on the edge of the frame and cut off differently in different exposures, thus making them seem brighter when more was present, and dimmer when most was cut off. That variation between frames drives up the uncertainty.
Perhaps more excitingly, it's possible that those stars in the blue region aren't having a large variation due to problems with our instruments, but because they're actual variable stars. I've already mentioned that there was already one known variable star, but that study was rather incomplete in comparison to the one we're conducting, and it's quite possible that we'll uncover more variable stars.
So now that we've located potential variable stars, we'll have to go back, make sure that the variation isn't caused by something else, and if they do turn out to be true variables, produce as much of a light curve as we can with our limited date in hopes that we can identify the type.
That's my story for the day. Tomrrow I'll probably be spending some time producing more CMDs from the 2MASS data we've obtained.
After finally going through all of the tedious photometry, my advisor has sent me some of the preliminary results. One of the things that we're looking to do, is create a color-magnitude diagram (CMD), essentially an HR Diagram, for NGC 7142. Last night, she put together one from the first round of subtraction (before I went back and with the second routine to get the remaining stars).
So here's an inside look at what's going on! First off, the CMD:
Sketched in here, is the main sequence (yellow) and the red giant branch (red). Keep in mind that this is still a very rough piece because there's still a good amount of calibration to be going through. The cluster will need to be dereddened (ie, the effects of the interstellar cloud accounted for and subtracted) which should help a lot of the scatter along the main sequence.
Additionally, this is instrumental magnitude, meaning how bright it appeared to our instruments. But since each instrument is different, it will eventually have to be brought to a standard system. That's another adventure to look forward to.
Both of these corrections (as well as possible others) will help make things look much prettier.
But that's not all I got today! I also got a plot of the error vs the instrumental magnitude in the V filter:
You'll notice there's a definate trend here in which the uncertainty goes up significantly the fainter the star is (fainter --> higher magnitude number --> further right).
But you'll notice there's a good number of stars on there in the bluish area I put in, that don't really fall on this trend. There's several reasons for this. One is that those stars could have been on the edge of the frame and cut off differently in different exposures, thus making them seem brighter when more was present, and dimmer when most was cut off. That variation between frames drives up the uncertainty.
Perhaps more excitingly, it's possible that those stars in the blue region aren't having a large variation due to problems with our instruments, but because they're actual variable stars. I've already mentioned that there was already one known variable star, but that study was rather incomplete in comparison to the one we're conducting, and it's quite possible that we'll uncover more variable stars.
So now that we've located potential variable stars, we'll have to go back, make sure that the variation isn't caused by something else, and if they do turn out to be true variables, produce as much of a light curve as we can with our limited date in hopes that we can identify the type.
That's my story for the day. Tomrrow I'll probably be spending some time producing more CMDs from the 2MASS data we've obtained.
Astronomical Pack Rats
A recent Universe Today article discussed the Discovery crew delivering supplies while taking out the trash. But take a look at the image and see what's lurking in the background.
That's right. It's the balloons I mentioned last month.
My question is, how have they managed to keep nylon balloons from deflating and will those be going out with the rest of the trash?
That's right. It's the balloons I mentioned last month.
My question is, how have they managed to keep nylon balloons from deflating and will those be going out with the rest of the trash?
South Dakota republicans don't even bother hiding it
The South Dakota Republicans have been hard at work drafting up their 2006 Resolutions.
The first 15 are rather typical of the Republican, involving the standard ass kissing of superiors, support of their own candidates (didn't see that coming...), gloating over holding all constitutional offices except one, ass kissing of the voters, restating positions loaded with logical fallacies, ignoring the seperation of church and state, homophobic tendencies, and the like, #16 stands out:
The next part in which they state it's taught as fact is a less used tactic, but wrong nonetheless. The fact that they don't understand that it's taught as a theory just goes to further the evidence that they didn't bother paying much attention in class or read their textbooks. Reviews of the most commonly textbook explicitly label evolution as a theory, not a fact. We honestly wonder if they've ever picked up a textbook (and no, that doesn't include the bible).
Furthermore, the claim that there are other "competing" theories again shows the deliberate misuse of the term "theory". There are no other scientific theories. But perhaps if they just keep pretending there are, God will answer their prayers.
And to further that claim, they state that Creationism is one of those "theories". Who cares that the Supreme Court ruled nearly 20 years ago that biblical Creationism is unconstitutional. Yet that's what they want topreach teach!
The first 15 are rather typical of the Republican, involving the standard ass kissing of superiors, support of their own candidates (didn't see that coming...), gloating over holding all constitutional offices except one, ass kissing of the voters, restating positions loaded with logical fallacies, ignoring the seperation of church and state, homophobic tendencies, and the like, #16 stands out:
Resolution 16:This statement is loaded with the typical intentional misuses of terminology, inappropriate blending of science and theology, and misunderstandings of how the educational system works. Let's examine it a bit closer:
WHEREAS, education on species origin is a vital aspect in the understanding of nature and the purpose of human life; and,
WHEREAS, evolution is a theory that is taught in public schools as fact and at the exclusion of all other theories; and
WHEREAS, the South Dakota Republican Party believes there are other plausible theories, including creationism;
THEREFORE, BE IT RESOLVED, the South Dakota Republican Party supports efforts to expand beyond evolution the knowledge, scope, and debate in public education on the theories of species origin.
education on species origin is a vital aspect in the understanding of nature and the purpose of human lifeThe resolution immediately begins by conveniently ignoring the fact that the origins discussions in classrooms are scientific in nature. They have to leave out of course, since bothering to recall that this is a scientific discussion would mean that things like the "purpose of human life" are irrelevant. But since when has honesty ever stopped them?
evolution is a theory that is taught in public schools as fact and at the exclusion of all other theoriesDid you catch it? The whole "evolution is a theory" bit? These guys really need some new tricks.
The next part in which they state it's taught as fact is a less used tactic, but wrong nonetheless. The fact that they don't understand that it's taught as a theory just goes to further the evidence that they didn't bother paying much attention in class or read their textbooks. Reviews of the most commonly textbook explicitly label evolution as a theory, not a fact. We honestly wonder if they've ever picked up a textbook (and no, that doesn't include the bible).
Furthermore, the claim that there are other "competing" theories again shows the deliberate misuse of the term "theory". There are no other scientific theories. But perhaps if they just keep pretending there are, God will answer their prayers.
the South Dakota Republican Party believes there are other plausible theories, including creationismAt least they're being honest, dispite being intentionally misleading. The use of the word "believe" explicitly shows that it's a matter of faith to them and has nothing to do with actual evidence or science.
And to further that claim, they state that Creationism is one of those "theories". Who cares that the Supreme Court ruled nearly 20 years ago that biblical Creationism is unconstitutional. Yet that's what they want to
the South Dakota Republican Party supports efforts to expand beyond evolution the knowledge, scope, and debate in public education on the theories of species originTranslation: Screw the scientific method, we want to be just like Kansas and include the supernatural!
And they were doing so well....
In the past, I've praised the Catholics for their support for good science. But it seems that they're still not there.
It seems that Cardinal Alfonso LĆ³pez Trujillo is wanting to excommunicate any catholic that is involved in stem cell research: "Excommunication will be applied to the women, doctors and researchers who eliminate embryos [and to the] politicians that approve the law."
I think the last quote of the article is one of the best I've ever read though:
It seems that Cardinal Alfonso LĆ³pez Trujillo is wanting to excommunicate any catholic that is involved in stem cell research: "Excommunication will be applied to the women, doctors and researchers who eliminate embryos [and to the] politicians that approve the law."
I think the last quote of the article is one of the best I've ever read though:
"This amounts to religious persecution of scientists," says Julian Savulescu, an ethicist at the University of Oxford. "Presumably God will be the one to judge the scientists, not Church leaders."
Evolution of Darwin's Finches
Historical legend posits that Darwin based his theory of evolution on observation of finches on the Galapagos islands. He was actually introduced to the idea by professor John Henslow while studying at Cambridge who had developed the basis while studying beatles and plants.
Dispite this bit of historical innacuracy, the finches have long been a staple of the story. And for the first time, scientists have observed real time changes in their beaks.
Due to the invasion of a new larger species that ate all the larger seeds, a new sub species with smaller beaks arose and flourished while the larger species almost perished due to lack of resources.
However, the article does have one false statement:
Dispite this bit of historical innacuracy, the finches have long been a staple of the story. And for the first time, scientists have observed real time changes in their beaks.
Due to the invasion of a new larger species that ate all the larger seeds, a new sub species with smaller beaks arose and flourished while the larger species almost perished due to lack of resources.
However, the article does have one false statement:
For the first time scientists have observed in real-time evolutionary changes in one species driven by competition for resources from anotherSuch evolutionary processes are frequently seen, but this one is only noteable for its novelty.
Thursday, July 13, 2006
Voting Rights
I don't blog too much on political issues, but every once in a while, I find something that some politican has been doing that leaves me wondering about the intellegence of my fellow humans (moreso than usual that is).
Fortunately, for the most part, this post is not one of those cases. The issue is that of voting rights. It seems that recently, the Voting Rights act of 1965 was up for renewal. The act prohibited discriminatory practices in allowing US citizens to vote. Such things would include sex, race, literacy, and other lines.
The act was upheld by the House with strong bipartisan support(390-33). However, there was some dissent. By who?
Southern conservatives of course.
Lynn Westmoreland of Georgia said, "By passing this rewrite of the Voting Rights Act, Congress is declaring from on high that states with voting problems 40 years ago can simply never be forgiven."
That's a cute interpretation, but is Mr. Westmoreland so naieve as to think that discrimination is something that ended 40 years ago? And do he and the other 32 that voted against the renewal forget all the incidents in southern states like Florida in which voters were illegally prevented from reaching the polling places? Yet somehow Florida didn't make it on the list of states that might need some federal oversight.
Fortunately, for the most part, this post is not one of those cases. The issue is that of voting rights. It seems that recently, the Voting Rights act of 1965 was up for renewal. The act prohibited discriminatory practices in allowing US citizens to vote. Such things would include sex, race, literacy, and other lines.
The act was upheld by the House with strong bipartisan support(390-33). However, there was some dissent. By who?
Southern conservatives of course.
Lynn Westmoreland of Georgia said, "By passing this rewrite of the Voting Rights Act, Congress is declaring from on high that states with voting problems 40 years ago can simply never be forgiven."
That's a cute interpretation, but is Mr. Westmoreland so naieve as to think that discrimination is something that ended 40 years ago? And do he and the other 32 that voted against the renewal forget all the incidents in southern states like Florida in which voters were illegally prevented from reaching the polling places? Yet somehow Florida didn't make it on the list of states that might need some federal oversight.
Gravity: "Just a theory"
One of the favourite claims of the ID/creationist crowd is that evolution and the big bang are "just theories" and that since theories have historically been replaced many times, there's no reaons to give any special credence to these inconsequential bits of short lived belief.
Fundamentally, this shows an enormous understanding of what constitutes a scientific theory. One of the most frequent ways that I respond when debating these pseudo-scientists is to remind them that "gravity is just a theory too."
Inevatibly, I get one of two responses. Either they deny that gravity is a theory, or claim that the evidence for it is overwhelming (which ironically, it is for evolution and the big bang as well) and thus, it's the best theory ever and some how not comparable to the other two.
But how sure are we about gravity?
The first major understanding of Gravity came in the Philosophiae Naturalis Principia Mathematica, written in 1687 by Isaac Newton. While people before then were assuredly familiary with gravity, Newtons workings were the first mathematical and scientific treatment of the topic.
Newton's work was a huge success in that it successfully explained a huge number of occurances. But perhaps most excitingly (at least to me) was it's ability to predict things that were far beyond the everyday understanding.
In the 1840's astronomers had been conducting careful observations of Uranus' orbit and noticed that it wasn't quite right. This meant that either Newton was wrong, or there was something strange going on. After careful analysis, two scientists, John Adams and Urbain Leverrier, independantly realized that the oddities could be explained by another, yet undiscovered planet. Additionally, they were able to predict where this planet should lie. Sure enough, Neptune was discovered!
(This is good science folks: Predictions made and verified!)
However, by the early 1900's, it was clear that Newton's theory had some problems. One of the main reasons was that the orbit of Mercury didn't "wobble" like it should.
Enter Einstein! In his most famous work, Einstein completely overhauled gravitational theory and fixed all the problems of the time by postulating that it was a curvature of space time. Several experiments later, Einstein was, like Newton, was vindicated, and the theory accepted.
However, 100 years later, it seems there may yet be room for revision!
Another favourite tactic of ID supporters is the "teach the controversy" mantra. However, in the scientific field, there is no statistically significant debate. But the same cannot be said for gravity. Currently there are several models working to append or supplant Einstein's work.
One of the major realizations is that, under extremely high energy densities (like what occured right after the big bang and today in particle accelerators), the four fundamnetal forces known (the strong and weak nuclear force, electromagnetism, and gravity) should all become a single unified force. However, while theories have been developed that relate the first three, gravity has been the odd man out and hasn't quite fit in.
In fact, while the other three forces are all similar in strength, gravity seems to be strangely "weak". Why gravity isn't as strong as the others is currently one of the unknowns. Thus, the newest theories working on fitting gravity into the bigger picture have suggested things like other dimentions which we cannot percieve that gravity can "leak" into.
So there's one major addtion to gravitational theory that's being reviewed.
But is it the only one? Not at all! Perhaps you've heard of something called Dark Matter? If not, it's a theory that states that ~3/4 of all matter in the universe is invisible and not interact with light for some reason. That means we can't see it giving off light, or absorbing light. So how do we know it's there?
That's where it relates to gravity. The first realization came by studying the orbit of stars around spiral galaxies. Under all current gravitational theories, it should work pretty much like the solar system: Stars close in orbit quickly whereas stars further out move slowly.
But observations say otherwise. Strangely enough, stars further out move almost as quickly as those further in. This has generally been interpreted to mean that there must be some more mass hidden somewhere.
However, that assumes that the gravitational models are correct. It's also possible that gravity may behave differently on such a scale. Thus, a modification to gravity has been proposed known as Modified Newtonian Dynamics (MOND). This hypothesis adds an extra term to Newton's equation for gravity that takes scale into account. Depending on how it's done, it can completely eliminate the need for dark matter, and possibly the even more enigmatic dark energy.
So as you can see, even the most universally accepted theory isn't immune to scrutiny when presented with evidence that runs contrary to the model. Meanwhile, evolutionary theory has yet to have a serious scientific challange levied agaisnt it.
Various unified models of gravity (espcially string theory) and MOND have a fair share of support in the scientific community. Surely far more than Intelligent Design, yet we don't ever see the ID crowd clamoring for an actual scientific controversy to be taught, only their own pet hypothesis. So much for intellectual honesty on their part.
Fundamentally, this shows an enormous understanding of what constitutes a scientific theory. One of the most frequent ways that I respond when debating these pseudo-scientists is to remind them that "gravity is just a theory too."
Inevatibly, I get one of two responses. Either they deny that gravity is a theory, or claim that the evidence for it is overwhelming (which ironically, it is for evolution and the big bang as well) and thus, it's the best theory ever and some how not comparable to the other two.
But how sure are we about gravity?
The first major understanding of Gravity came in the Philosophiae Naturalis Principia Mathematica, written in 1687 by Isaac Newton. While people before then were assuredly familiary with gravity, Newtons workings were the first mathematical and scientific treatment of the topic.
Newton's work was a huge success in that it successfully explained a huge number of occurances. But perhaps most excitingly (at least to me) was it's ability to predict things that were far beyond the everyday understanding.
In the 1840's astronomers had been conducting careful observations of Uranus' orbit and noticed that it wasn't quite right. This meant that either Newton was wrong, or there was something strange going on. After careful analysis, two scientists, John Adams and Urbain Leverrier, independantly realized that the oddities could be explained by another, yet undiscovered planet. Additionally, they were able to predict where this planet should lie. Sure enough, Neptune was discovered!
(This is good science folks: Predictions made and verified!)
However, by the early 1900's, it was clear that Newton's theory had some problems. One of the main reasons was that the orbit of Mercury didn't "wobble" like it should.
Enter Einstein! In his most famous work, Einstein completely overhauled gravitational theory and fixed all the problems of the time by postulating that it was a curvature of space time. Several experiments later, Einstein was, like Newton, was vindicated, and the theory accepted.
However, 100 years later, it seems there may yet be room for revision!
Another favourite tactic of ID supporters is the "teach the controversy" mantra. However, in the scientific field, there is no statistically significant debate. But the same cannot be said for gravity. Currently there are several models working to append or supplant Einstein's work.
One of the major realizations is that, under extremely high energy densities (like what occured right after the big bang and today in particle accelerators), the four fundamnetal forces known (the strong and weak nuclear force, electromagnetism, and gravity) should all become a single unified force. However, while theories have been developed that relate the first three, gravity has been the odd man out and hasn't quite fit in.
In fact, while the other three forces are all similar in strength, gravity seems to be strangely "weak". Why gravity isn't as strong as the others is currently one of the unknowns. Thus, the newest theories working on fitting gravity into the bigger picture have suggested things like other dimentions which we cannot percieve that gravity can "leak" into.
So there's one major addtion to gravitational theory that's being reviewed.
But is it the only one? Not at all! Perhaps you've heard of something called Dark Matter? If not, it's a theory that states that ~3/4 of all matter in the universe is invisible and not interact with light for some reason. That means we can't see it giving off light, or absorbing light. So how do we know it's there?
That's where it relates to gravity. The first realization came by studying the orbit of stars around spiral galaxies. Under all current gravitational theories, it should work pretty much like the solar system: Stars close in orbit quickly whereas stars further out move slowly.
But observations say otherwise. Strangely enough, stars further out move almost as quickly as those further in. This has generally been interpreted to mean that there must be some more mass hidden somewhere.
However, that assumes that the gravitational models are correct. It's also possible that gravity may behave differently on such a scale. Thus, a modification to gravity has been proposed known as Modified Newtonian Dynamics (MOND). This hypothesis adds an extra term to Newton's equation for gravity that takes scale into account. Depending on how it's done, it can completely eliminate the need for dark matter, and possibly the even more enigmatic dark energy.
So as you can see, even the most universally accepted theory isn't immune to scrutiny when presented with evidence that runs contrary to the model. Meanwhile, evolutionary theory has yet to have a serious scientific challange levied agaisnt it.
Various unified models of gravity (espcially string theory) and MOND have a fair share of support in the scientific community. Surely far more than Intelligent Design, yet we don't ever see the ID crowd clamoring for an actual scientific controversy to be taught, only their own pet hypothesis. So much for intellectual honesty on their part.
Patterns from the Void
In an effort to find things to discuss on this blog, I'm frequently looking through many sites. Recently, I've been doing this while waiting for the computer to finish running a script (which takes a few minutes), so instead of writing up a full post right then and there, I generally Email myself links to remind myself of potential topics. It's also nice in that it gives me some time to compose my thoughts.
Today I noticed that a number of the links I'd sent myself all seem to have a common theme, namely that people like to attribute meaning to imagined patterns in something that is completely random. Given that this ability is so frequent, I'll have to ask forgivness if I start sounding a bit ranty.
A number of the sources I look at recently have been reporting about an egg that was laid that bears the name "Allah" in Arabic. Being the skeptic that I am, I wanted to see just how clearly this was written out. Unfortunately, Reuters (the site on which I found the story) didn't have a picture. So I did some digging and here's what I found:
To me, no distinguishable pattern jumps out at me. But then again, I wasn't sure what "Allah" looks like in Arabic. Fortunately, google was able to provide answers. "Allah" looks like this:
So now I know what I'm looking for. Looking back at the egg, I'm still not seeing it. Not discouraged, I went to seek out a website on which someone had betterimagination eyes than I and would point it out.
Back to google it was! Sadly, I wasn't able to find a single website that could point it out to me. But what I did find was a website that found squiggly double u's all over the place! Perhaps I should rethink this whole atheism thing and convert to Islam.
But wait. What about all those occurances of Christian symbols I mentioned at the beginning of my post?! Surely that must be a sign that Christianity is the one true religion!
So the hunt to see which religion can claim the most vaguely reminiscant religious iconography was on!
Back to google, I searched for "Jesus appears in" and to see how our good friendly loving Christians were doing.
Apparently he doesn't have anything to do besides appear in wardrobes (ooh naughty), a spit take, dental x-rays, car winshields, a rock for sale on Ebay, a plant, a waterstain in someone's shower, and a whole bunch of trees.
But let's not forget that Jesus isn't the only Christian figure that's prone to popping up in unexpected places. I'd heard of the Virgin Mary showing up occiasionally, so I did a quick search for "Mary appears in". Seems she has been known to frequent window glares, mirrors, and like her son, water stains.
And then I found this site and quit. That sight has enough images to hands down report that Christians are the mostgullable likely group to recieve miracles. Thus, I'm officially declaring myself Christian. After all, none of the images could possibly be hoaxes or simply reading too much into things. Right?
That'd be a nice thing to believe, but sadly, the evidence suggests otherwise. Not too long ago there was a Jesus pancake that appeared for sale on Ebay. True believers jumped all over it, driving the auction to nearly $15,000 before Ebay closed it. So where did the image come from? The trusty Jesus Pan of course.
So it's entirely possible to be taken in by scams. But this doesn't eliminate every sighting out there. However, the ability to see paterns in randomness and assign meaning is astounding. It's why people can find dragons in clouds, or inappropriate gestures in nebulae. It's the ability to assign meaning to nonsense that allows people like Richard Hoagland to "discover" pyramids on mars and other bizzare things. It's this ability that allowed the ancient civilizationt to discern patterns amidst the stars giving us constellations. There's thousands of examples of people assigning meaning to that which has none. But the track record being against them has never stopped someone who really wants to see what isn't there. Reality be damned. It's more fun to believe.
I even had a personal experience with a disturbing sign recently that I thought I'd share. Given the horrendous nature of the dorm food here, I've been frequenting Jack in the Box as of late. But to my surpise, my large Ultimate Cheesburger combo with curly fries gave me an ominous total: $6.66. And did I forget to mention it's the #6 combo? Perhaps God is telling me that I need to lay off the fast food and eat some veggies?
Today I noticed that a number of the links I'd sent myself all seem to have a common theme, namely that people like to attribute meaning to imagined patterns in something that is completely random. Given that this ability is so frequent, I'll have to ask forgivness if I start sounding a bit ranty.
A number of the sources I look at recently have been reporting about an egg that was laid that bears the name "Allah" in Arabic. Being the skeptic that I am, I wanted to see just how clearly this was written out. Unfortunately, Reuters (the site on which I found the story) didn't have a picture. So I did some digging and here's what I found:
To me, no distinguishable pattern jumps out at me. But then again, I wasn't sure what "Allah" looks like in Arabic. Fortunately, google was able to provide answers. "Allah" looks like this:
So now I know what I'm looking for. Looking back at the egg, I'm still not seeing it. Not discouraged, I went to seek out a website on which someone had better
Back to google it was! Sadly, I wasn't able to find a single website that could point it out to me. But what I did find was a website that found squiggly double u's all over the place! Perhaps I should rethink this whole atheism thing and convert to Islam.
But wait. What about all those occurances of Christian symbols I mentioned at the beginning of my post?! Surely that must be a sign that Christianity is the one true religion!
So the hunt to see which religion can claim the most vaguely reminiscant religious iconography was on!
Back to google, I searched for "Jesus appears in" and to see how our good friendly loving Christians were doing.
Apparently he doesn't have anything to do besides appear in wardrobes (ooh naughty), a spit take, dental x-rays, car winshields, a rock for sale on Ebay, a plant, a waterstain in someone's shower, and a whole bunch of trees.
But let's not forget that Jesus isn't the only Christian figure that's prone to popping up in unexpected places. I'd heard of the Virgin Mary showing up occiasionally, so I did a quick search for "Mary appears in". Seems she has been known to frequent window glares, mirrors, and like her son, water stains.
And then I found this site and quit. That sight has enough images to hands down report that Christians are the most
That'd be a nice thing to believe, but sadly, the evidence suggests otherwise. Not too long ago there was a Jesus pancake that appeared for sale on Ebay. True believers jumped all over it, driving the auction to nearly $15,000 before Ebay closed it. So where did the image come from? The trusty Jesus Pan of course.
So it's entirely possible to be taken in by scams. But this doesn't eliminate every sighting out there. However, the ability to see paterns in randomness and assign meaning is astounding. It's why people can find dragons in clouds, or inappropriate gestures in nebulae. It's the ability to assign meaning to nonsense that allows people like Richard Hoagland to "discover" pyramids on mars and other bizzare things. It's this ability that allowed the ancient civilizationt to discern patterns amidst the stars giving us constellations. There's thousands of examples of people assigning meaning to that which has none. But the track record being against them has never stopped someone who really wants to see what isn't there. Reality be damned. It's more fun to believe.
I even had a personal experience with a disturbing sign recently that I thought I'd share. Given the horrendous nature of the dorm food here, I've been frequenting Jack in the Box as of late. But to my surpise, my large Ultimate Cheesburger combo with curly fries gave me an ominous total: $6.66. And did I forget to mention it's the #6 combo? Perhaps God is telling me that I need to lay off the fast food and eat some veggies?
Astronomy Internship - Day 34
I finished checking the subtractions today and they all look pretty good. With the exception of the B filters again. Thus, I proceeded with the next step which was to run through the process again, catching stars that were too close to others to get the first time around. I got through 12 of the images this afternoon, and should be finished with them tomorrow morning.
With that, I should be able to start actually producing some graphs and analyzing the structure of the color magnitude diagram (essentially a HR diagram). So after a month of work, it looks like I'm finally about to get some real science out of all this.
Meanwhile, I've been reading over a paper regarding my other project and looking at how we're going to be treating the data from the 2MASS survey in order to study the cluster in the JHK bands (infrared filters). The paper is slowly starting to make sense, but I'm sure when I actually start working with the data and seeing what they're doing, it will become even more clear. That's generally how things work for me.
With that, I should be able to start actually producing some graphs and analyzing the structure of the color magnitude diagram (essentially a HR diagram). So after a month of work, it looks like I'm finally about to get some real science out of all this.
Meanwhile, I've been reading over a paper regarding my other project and looking at how we're going to be treating the data from the 2MASS survey in order to study the cluster in the JHK bands (infrared filters). The paper is slowly starting to make sense, but I'm sure when I actually start working with the data and seeing what they're doing, it will become even more clear. That's generally how things work for me.
Astronomy Internship - Day 33
Being finished with the first step of data reduction, I'm now going back through each image and looking to see how good of a job the routines did of subtracting all the stars. When I first started playing with these programs, it was catching about 96% of the light from the stars, which means that there would be a 4% systematic error in the results. Not good. Most good astronomy is done at or below the 1% level, which is why I spent so much time tinkering with the program at the outset.
But it seems now that things worked pretty well. In all of the frames, the bottom 1/3 of the image is not well focused, which means that the fitting routine doesn't do as well. For most images, we still have that <1% residual, but a few are larger. In particular, the images taken in the B filter are the worst. Unfortunately, it doesn't look like much can be done about this.
To do this error checking, I have to take the image, and look at the intensity of the star before and after the subtraction. Ideally it should go to zero. Sometimes it doesn't quite get everything, and other times, it overestimates how bright the star was and subtracts too much. To get a real good feeling, I divide the images into 9 pieces mentally (a 3x3 grid) and pick the brightest star from each one to check.
At some point, I'll try to go through the concept behind the process of what I've been doing thus far. Conceptually it's not too hard, but it would be best explained with some pretty images.
I only ended up making it through about half of the 21 images to check. Then we headed to the beach again. Waves were much better, but I couldn't borrow a boogie board and ended up body surfing (which is fun nonetheless).
But it seems now that things worked pretty well. In all of the frames, the bottom 1/3 of the image is not well focused, which means that the fitting routine doesn't do as well. For most images, we still have that <1% residual, but a few are larger. In particular, the images taken in the B filter are the worst. Unfortunately, it doesn't look like much can be done about this.
To do this error checking, I have to take the image, and look at the intensity of the star before and after the subtraction. Ideally it should go to zero. Sometimes it doesn't quite get everything, and other times, it overestimates how bright the star was and subtracts too much. To get a real good feeling, I divide the images into 9 pieces mentally (a 3x3 grid) and pick the brightest star from each one to check.
At some point, I'll try to go through the concept behind the process of what I've been doing thus far. Conceptually it's not too hard, but it would be best explained with some pretty images.
I only ended up making it through about half of the 21 images to check. Then we headed to the beach again. Waves were much better, but I couldn't borrow a boogie board and ended up body surfing (which is fun nonetheless).
Astronomy Internship - Day 32
I'm FINALLY finished with the first stage of reduction of these images! As a reward, I gave myself the rest of the day off since I was pushing myself to get 4 images done a day instead of my normal two. Being able to set my own schedule is wonderful.
After working, some of the group and I headed to the beach again. The waves were disappointing as I'm a fan of boogy-boarding and am looking to learn how to surf here eventually.
And for those that look forward to these updates on what goes on in the life of an astronomer, I apologize for them going up late occasionally. I typically write them throughout the day as I'm doing things, save them, and frequently forget to finish and post them at night. Then a few days later I'll remember that I still haven't posted some, hence the sudden post rush of three days all at once.
After working, some of the group and I headed to the beach again. The waves were disappointing as I'm a fan of boogy-boarding and am looking to learn how to surf here eventually.
And for those that look forward to these updates on what goes on in the life of an astronomer, I apologize for them going up late occasionally. I typically write them throughout the day as I'm doing things, save them, and frequently forget to finish and post them at night. Then a few days later I'll remember that I still haven't posted some, hence the sudden post rush of three days all at once.
Tuesday, July 11, 2006
Spiritual experiences akin to hallucination
According to The Independant a group of researchers have shown that hallucinogenic drugs can cause expeiences identical to experiences that a frequently considered "spiritual" when not induced by drugs.
I would say that this is a "no duh" experiment since the use of drugs to cause spiritual journeys has long been practice of many groups. Historically it was has been used by Native American tribes, but has also been in the news recently for a Supreme Court battle over whether or not hallucinognic teas should be allowed for a Brazillian church, and a lesser court battle over a church worshiping their god through use of marijuana.
However, the study also goes on to note that many of those that used the drugs had improved moods and well being for as long as two months. I wonder how scientologists will spin this to their "drugs are bad mmkay" agenda.
Meanwhile, the reasearchers say they have no interest in the debate on whether or not God exists, and that their research "can't and won't go there." I agree that it can't answer that question, but it is yet another piece of evidence that mystical experiences can be fully explained without having to invoke the supernatural.
I would say that this is a "no duh" experiment since the use of drugs to cause spiritual journeys has long been practice of many groups. Historically it was has been used by Native American tribes, but has also been in the news recently for a Supreme Court battle over whether or not hallucinognic teas should be allowed for a Brazillian church, and a lesser court battle over a church worshiping their god through use of marijuana.
However, the study also goes on to note that many of those that used the drugs had improved moods and well being for as long as two months. I wonder how scientologists will spin this to their "drugs are bad mmkay" agenda.
Meanwhile, the reasearchers say they have no interest in the debate on whether or not God exists, and that their research "can't and won't go there." I agree that it can't answer that question, but it is yet another piece of evidence that mystical experiences can be fully explained without having to invoke the supernatural.
Monday, July 10, 2006
Astronomy Internship - Day 31
I ended up getting another 3 images finished today. That leaves me with 5 to go so I should be done Wednesday and ready to move onto the next step.
I also found out that I'm going to be working on another project here with NGC 7142. Instead of looking at the cluster in the standard UBV filter system, we're going to use data from the 2 Micron All Sky Survey (2MASS) and try to get a better understanding of the cluster.
The advantage in using the infrared is that it's less affected by the interstellar cloud lying in front of the cluster.
What we're primarily looking to do is fit this cluster's HR diagram with the theoretical one. The reddening caused by the interstellar cloud shifts things right because it makes objects appear redder. It also shifts things down because it makes things appear dimmer.
So we'll be trying to figure out how to properly move thigns back up and to the left on that diagram.
But with using the infrared, there's another problem we'll be facing. Since the majority of stars in the galaxy are low mass, red stars (as much as 90% of all stars are this), looking at things in the infrared will bring out a lot more. That's good for looking at the cluster, but since the cluster lies in Cepheus, which is near the plane of the milky way, it's a crowded star field, and thus, more stars are going to be popping out that aren't necessarily assosciated with the cluster and will contaminate the results.
My advisor and I are currently working on trying to figure out how to avoid this.
What we're really looking for is the location of the Red Giant Branch (RGB) which, as I'll explain in my next post on astronomical data and analysis, will be able to help us determine the age of the cluster.
I also found out that I'm going to be working on another project here with NGC 7142. Instead of looking at the cluster in the standard UBV filter system, we're going to use data from the 2 Micron All Sky Survey (2MASS) and try to get a better understanding of the cluster.
The advantage in using the infrared is that it's less affected by the interstellar cloud lying in front of the cluster.
What we're primarily looking to do is fit this cluster's HR diagram with the theoretical one. The reddening caused by the interstellar cloud shifts things right because it makes objects appear redder. It also shifts things down because it makes things appear dimmer.
So we'll be trying to figure out how to properly move thigns back up and to the left on that diagram.
But with using the infrared, there's another problem we'll be facing. Since the majority of stars in the galaxy are low mass, red stars (as much as 90% of all stars are this), looking at things in the infrared will bring out a lot more. That's good for looking at the cluster, but since the cluster lies in Cepheus, which is near the plane of the milky way, it's a crowded star field, and thus, more stars are going to be popping out that aren't necessarily assosciated with the cluster and will contaminate the results.
My advisor and I are currently working on trying to figure out how to avoid this.
What we're really looking for is the location of the Red Giant Branch (RGB) which, as I'll explain in my next post on astronomical data and analysis, will be able to help us determine the age of the cluster.
Astronomy Internship - Day 30
Today I didn't really do much exciting. Most of my day was spent working on the post regarding the HR diagram. Other than that, nothing fun.
Sunday, July 09, 2006
In the cookie jar again
The other day I posted about how, dispite their claims to the contrary, Christians have a history of viscously persecuting those that disagree with them. It may no longer be a full scale crusade, but the tradition continues.
I first mentioned Joann Bell's case in which she and her children were assaulted and her house was eventually burned.
I then posted about a Jewish family who was forced to flee their town due to fear of reprisal for a lawsuit to uphold the constitution.
But these aren't the only cases. In Oklahoma, another case has been brewing over two years in which a girl was kicked off a sports team at her high school for refusing to participate in a state sponsored prayer.
Her father went to talk to the principal and a scuffle ensued. The man then told he could leave the town (where he could no longer file charges against the school for his daughter's removal from the team), or face charges himself for battery.
He chose to face the gauntlet and was charged with a felony count of battery. Eventually he was found not guilty on all counts but the process to get such a verdict in a town full of "loving" (read: bloodthirsty) Christians was a difficult one.
He describes lawyers refusing to properly represent him or give him pertinant legal information, threats, and brush fires suspiciously starting upwind of his home.
So if you have some time, read over his testimony. It's not the most coherent piece of prose, but then again, how focused would you really be after a two year ordeal in which your family's lives were on the line, simply because you were an atheist and wished to uphold the constitution?
I first mentioned Joann Bell's case in which she and her children were assaulted and her house was eventually burned.
I then posted about a Jewish family who was forced to flee their town due to fear of reprisal for a lawsuit to uphold the constitution.
But these aren't the only cases. In Oklahoma, another case has been brewing over two years in which a girl was kicked off a sports team at her high school for refusing to participate in a state sponsored prayer.
Her father went to talk to the principal and a scuffle ensued. The man then told he could leave the town (where he could no longer file charges against the school for his daughter's removal from the team), or face charges himself for battery.
He chose to face the gauntlet and was charged with a felony count of battery. Eventually he was found not guilty on all counts but the process to get such a verdict in a town full of "loving" (read: bloodthirsty) Christians was a difficult one.
He describes lawyers refusing to properly represent him or give him pertinant legal information, threats, and brush fires suspiciously starting upwind of his home.
So if you have some time, read over his testimony. It's not the most coherent piece of prose, but then again, how focused would you really be after a two year ordeal in which your family's lives were on the line, simply because you were an atheist and wished to uphold the constitution?
Astronomical Data 3a. – The H-R Diagram
Now that we’ve taken a look at what light is, where it comes from, how we detect it, and how we calibrate things, we’ve finally set enough groundwork to begin to say what we can learn and how?
In astronomy almost all of the information comes from light, so you can probably guess there’s a lot we can learn. Using nothing but the properties of the light, astronomers can measure the velocity of objects towards us or away from us, magnetic fields, chemical composition, temperature, and more.
So in this next series of posts, we’ll explore how light yields all these secrets.
The first topic that I feel should be discussed, is one that I mentioned in my post yesterday about Mt. Wilson observatory. This is the Hertzsprung Russell Diagram (HR Diagram) which, as I mentioned, is fundamental to the understanding of all stellar evolution.
In its simplest form, an HR diagram is simply a plot of a number of stars with their brightness on the y-axis, and their temperature on the x-axis. Thus, to really discuss it, I’ll have to speak about both of these properties, so this post will be a two for one deal.
Before I get started at giving away the answers, and if you don’t already know them, try to take a bit of time to figure out what an HR diagram should look like and why it should look that way.
Where will stars lie? Will they all be clumped? Will there be a trend line? Or will stars be evenly distributed everywhere?
What properties of the star will determine its position? Size? Magnetic fields? Rotation? Age? Chemical composition?
Once you’ve outlined your hypothesis, keep it in mind as we go.
So let’s get started on figuring out how to build an HR diagram from observations. The first thing we must do is to choose which stars to observe. This is more important than you’d think at first, because we have to choose stars that we either know the distance to so that we can correct for the light becoming dimmer due to distance, or choose stars that are all at the same distance so we don’t have to worry about corrections.
It’s possible to do either. The best way to do the former (stars for which we know the distance accurately) is to look at the closest stars. For these the distance is known extremely accurately because it’s possible to use a technique known as astronomical parallax to determine their distance.
Effectively this technique is the same as holding a finger up at arms length and then closing each eye. By observing the apparent change in position in relation to extremely distant objects and knowing the separation between your to observing points (in this case your eyes), you can determine the distance to the object in question because you’ve just formed a very nice little triangle. From that, you can make a right triangle and we should all know about those guys from high school.
The same thing works in astronomy, except, instead of using our baseline as the distance between our eyes, we use one that’s 186,000,000 miles: the diameter of Earth’s orbit.
As you can see, we’ll observe a star with relation to background objects at one point, wait 6 months, and do it again. The lower part of the image demonstrates that the star will move. The amount it moves gives the “parallax angle” which can be used to determine the distance. Obviously, the further away a star is, the less it will seem to move, which makes the angle harder to measure.
With the launch of the Hipparcos satellite there are roughly 100,000 stars for which we have precise parallax measurements for. That’s a pretty damn good sample of stars for which we can to make our HR diagram!
The other option is to choose a grouping of stars that all have the same distance so we don’t have to worry about some being more dimmed than others due to distance. Fortunately clusters have lots of stars that are all at the same distance.
So now that we’ve figured out which stars to choose, it’s time to measure their brightness. Before the advent of CCDs, this was quite tricky using photographic film, or quite slow using photomultipliers (which can only do one star at a time).
But fortunately CCDs allow us to determine brightnesses of a whole field of stars at once! All we have to do is count up how many photons hit the CCD and we get its apparent magnitude. We can then take the apparent magnitude and put it on a standard scale which fixes all stars for the same distance (in the former case) which is it’s absolute magnitude (the magnitude of a star viewed from a distance of 10 parsecs).
If we’re looking at one of those clusters, then we don’t have to worry about correcting for distance and are finished with figuring out what we need for the y-axis.
The next trick is to figure out the temperature of the star. Fortunately, this isn’t hard either.
If you remember back to my post on where light comes from, it’s caused by electrons in higher orbitals falling down.
What I didn’t tell you is what determines how electrons get in those higher orbitals. There’s two primary ways: The electron can get excited by getting hit by another photon, or it can get bumped up in a collision with another atom.
Both of those two cases are directly related to what we need: Temperature.
For a given temperature electrons are most commonly bumped up to a single orbital, although not always. Thus, when you look at how much light is given off at every wavelength, there will be one at which it peaks.
So if we can find this peak, we can determine the temperature. There’s a few different methods for doing this, which I’ll go into in detail in a later post.
So now we’ve been able to get both temperature and brightness. We’re ready to construct our HR diagram!
Before I show you the image, think back to what your hypothesis was and see if you were right.
Before I go any further, I feel it’s important to point out that the x-axis runs backwards. Higher temperatures are to the left. The reason for this has to do with a convention on another property I’ll discuss later that is actually interchangeable with temperature.
This image is from the ESO, and I suspect it’s a plot of the nearest stars. Ones for clusters have a distinct difference which I’ll discuss in my next post on this topic.
Looking at this very quickly, you can tell that the stars do indeed fall along a main line running diagonally from the upper left to the lower right. This line is known as the main sequence and is where stars spend 90% of their lives while they quietly burn hydrogen into helium in their cores. The other clumps I’ll go into at a later time.
But let’s explore what this graph is telling us before going any further. Stars to the left are the hottest. To the right they are the coolest. Towards the top they are brighter than at the bottom. Thus, a star in the upper left hand corner, is a very hot, bright star.
Hotter stars are obviously going to be brighter. But why then, do we see some cool stars that are almost as bright that are very cool (towards the upper right)? If temperature isn’t causing them to be brighter, what is?
The answer is that these stars are just larger than the average star. Since they’re larger, that means that they have more surface area to give off light, which is why they seem brighter. So stars in the upper right are giants, while stars in the lower left are dwarf.
So what else can we figure out from this diagram? Another thing that we can plot on this graph is the color of the star. Yes, stars do have color. Our eyes aren’t terribly sensitive to these colors, but if you really pay attention, you’ll see it. The bright star Sirius (which is up for those of us in the Northern hemisphere tonight, just to the southwest of the extremely bright Jupiter) is a blue star. Meanwhile, the star straight up from Orion’s belt (visible in fall and winter), Betelgeuse, is a dingy red.
Since Wein’s Law I mentioned earlier tells us that the peak wavelength is dependant on temperature, color and temperature can be used rather interchangeably. Hot stars have their peak wavelength at shorter wavelengths (ie, blue) since their photons should understandably have more energy. The opposite is also true with cool stars being red (long wavelength). The Sun is actually somewhere in the middle, with its peak wavelength being a sort of lime green.
Incidentally, this is the precise wavelength to which our eyes have evolved to be most sensitive at. Since your eyes are extra sensitive to that wavelength of light, newer fire trucks are being panted that color so they’ll stand out. Awful color, but it sure is noticeable.
You may have heard terms like “Red Dwarf” before. Now you should be able to get an idea of where these come from. They’re positions on this diagram. A red dwarf would be a red star towards the lower right. “White Dwarves” would be ones that were closer to the blue end, but still very small.
So let’s take another look at the HR diagram with those features plotted as well.
Again, pay no attention to the x-axis where it speaks of Spectral Class. I’ll explain that when I start getting into chemical composition and the spectra of stars.
But here we can see more clearly how size and color progress, as well as how a few popular stars like Betelgeuse, Sirius, Vega, and others stack up.
But not pictured on here, and still not discussed is one more important feature that we can plot: Mass.
To figure out how that would figure in, let’s stop to consider why stars are, well, stars. Even without taking a hunch of courses in astronomy, you’re probably well aware that stars are accumulations of (mostly) hydrogen gas that’s hot enough to undergo nuclear fusion in its core. But why are they so hot?
The reason has to do with where they come from. Stars (and their respective solar systems) start off as giant clouds of gas, lightyears across. Eventually, the cloud collapses under its own gravity. Bur remember how I discussed gravitational potential energy when talking about electron orbitals? The cloud has a net potential energy as well.
As everything collapses from something light years across to only a few million miles, there is a huge release of that potential energy. It is converted (at least in part) to heat.
So where does mass factor in to all of this? The answer is that the more mass there is, the more gravitational potential energy it has. Thus, more mass leads to more energy converted to heat, which means higher temperature! Cutting out the middle steps, and reversing it, hot stars are more massive.
I couldn’t find an image with this plotted on it, so I’ll just let you use your imagination.
So that’s an introduction to the HR diagram. By finding a star’s temperature (which is synonymous with color and something called spectral class), and its luminosity, we can figure out the mass and the size!
Suddenly this two for one post deal became a 4 for 1. Not bad.
Since the HR diagram we looked at today was generated by the closest stars, next time I post on the topic of how we learn things in astronomy, I’ll talk about a difference in these for when we look at stars in clusters. This difference gives us another important feature of the stars in that cluster: Age.
I’ll probably get that up in a few days since tomorrow’s Monday and I’ll be heading back to work on research, meaning I won’t have as much free time.
In astronomy almost all of the information comes from light, so you can probably guess there’s a lot we can learn. Using nothing but the properties of the light, astronomers can measure the velocity of objects towards us or away from us, magnetic fields, chemical composition, temperature, and more.
So in this next series of posts, we’ll explore how light yields all these secrets.
The first topic that I feel should be discussed, is one that I mentioned in my post yesterday about Mt. Wilson observatory. This is the Hertzsprung Russell Diagram (HR Diagram) which, as I mentioned, is fundamental to the understanding of all stellar evolution.
In its simplest form, an HR diagram is simply a plot of a number of stars with their brightness on the y-axis, and their temperature on the x-axis. Thus, to really discuss it, I’ll have to speak about both of these properties, so this post will be a two for one deal.
Before I get started at giving away the answers, and if you don’t already know them, try to take a bit of time to figure out what an HR diagram should look like and why it should look that way.
Where will stars lie? Will they all be clumped? Will there be a trend line? Or will stars be evenly distributed everywhere?
What properties of the star will determine its position? Size? Magnetic fields? Rotation? Age? Chemical composition?
Once you’ve outlined your hypothesis, keep it in mind as we go.
So let’s get started on figuring out how to build an HR diagram from observations. The first thing we must do is to choose which stars to observe. This is more important than you’d think at first, because we have to choose stars that we either know the distance to so that we can correct for the light becoming dimmer due to distance, or choose stars that are all at the same distance so we don’t have to worry about corrections.
It’s possible to do either. The best way to do the former (stars for which we know the distance accurately) is to look at the closest stars. For these the distance is known extremely accurately because it’s possible to use a technique known as astronomical parallax to determine their distance.
Effectively this technique is the same as holding a finger up at arms length and then closing each eye. By observing the apparent change in position in relation to extremely distant objects and knowing the separation between your to observing points (in this case your eyes), you can determine the distance to the object in question because you’ve just formed a very nice little triangle. From that, you can make a right triangle and we should all know about those guys from high school.
The same thing works in astronomy, except, instead of using our baseline as the distance between our eyes, we use one that’s 186,000,000 miles: the diameter of Earth’s orbit.
As you can see, we’ll observe a star with relation to background objects at one point, wait 6 months, and do it again. The lower part of the image demonstrates that the star will move. The amount it moves gives the “parallax angle” which can be used to determine the distance. Obviously, the further away a star is, the less it will seem to move, which makes the angle harder to measure.
With the launch of the Hipparcos satellite there are roughly 100,000 stars for which we have precise parallax measurements for. That’s a pretty damn good sample of stars for which we can to make our HR diagram!
The other option is to choose a grouping of stars that all have the same distance so we don’t have to worry about some being more dimmed than others due to distance. Fortunately clusters have lots of stars that are all at the same distance.
So now that we’ve figured out which stars to choose, it’s time to measure their brightness. Before the advent of CCDs, this was quite tricky using photographic film, or quite slow using photomultipliers (which can only do one star at a time).
But fortunately CCDs allow us to determine brightnesses of a whole field of stars at once! All we have to do is count up how many photons hit the CCD and we get its apparent magnitude. We can then take the apparent magnitude and put it on a standard scale which fixes all stars for the same distance (in the former case) which is it’s absolute magnitude (the magnitude of a star viewed from a distance of 10 parsecs).
If we’re looking at one of those clusters, then we don’t have to worry about correcting for distance and are finished with figuring out what we need for the y-axis.
The next trick is to figure out the temperature of the star. Fortunately, this isn’t hard either.
If you remember back to my post on where light comes from, it’s caused by electrons in higher orbitals falling down.
What I didn’t tell you is what determines how electrons get in those higher orbitals. There’s two primary ways: The electron can get excited by getting hit by another photon, or it can get bumped up in a collision with another atom.
Both of those two cases are directly related to what we need: Temperature.
For a given temperature electrons are most commonly bumped up to a single orbital, although not always. Thus, when you look at how much light is given off at every wavelength, there will be one at which it peaks.
So if we can find this peak, we can determine the temperature. There’s a few different methods for doing this, which I’ll go into in detail in a later post.
So now we’ve been able to get both temperature and brightness. We’re ready to construct our HR diagram!
Before I show you the image, think back to what your hypothesis was and see if you were right.
Before I go any further, I feel it’s important to point out that the x-axis runs backwards. Higher temperatures are to the left. The reason for this has to do with a convention on another property I’ll discuss later that is actually interchangeable with temperature.
This image is from the ESO, and I suspect it’s a plot of the nearest stars. Ones for clusters have a distinct difference which I’ll discuss in my next post on this topic.
Looking at this very quickly, you can tell that the stars do indeed fall along a main line running diagonally from the upper left to the lower right. This line is known as the main sequence and is where stars spend 90% of their lives while they quietly burn hydrogen into helium in their cores. The other clumps I’ll go into at a later time.
But let’s explore what this graph is telling us before going any further. Stars to the left are the hottest. To the right they are the coolest. Towards the top they are brighter than at the bottom. Thus, a star in the upper left hand corner, is a very hot, bright star.
Hotter stars are obviously going to be brighter. But why then, do we see some cool stars that are almost as bright that are very cool (towards the upper right)? If temperature isn’t causing them to be brighter, what is?
The answer is that these stars are just larger than the average star. Since they’re larger, that means that they have more surface area to give off light, which is why they seem brighter. So stars in the upper right are giants, while stars in the lower left are dwarf.
So what else can we figure out from this diagram? Another thing that we can plot on this graph is the color of the star. Yes, stars do have color. Our eyes aren’t terribly sensitive to these colors, but if you really pay attention, you’ll see it. The bright star Sirius (which is up for those of us in the Northern hemisphere tonight, just to the southwest of the extremely bright Jupiter) is a blue star. Meanwhile, the star straight up from Orion’s belt (visible in fall and winter), Betelgeuse, is a dingy red.
Since Wein’s Law I mentioned earlier tells us that the peak wavelength is dependant on temperature, color and temperature can be used rather interchangeably. Hot stars have their peak wavelength at shorter wavelengths (ie, blue) since their photons should understandably have more energy. The opposite is also true with cool stars being red (long wavelength). The Sun is actually somewhere in the middle, with its peak wavelength being a sort of lime green.
Incidentally, this is the precise wavelength to which our eyes have evolved to be most sensitive at. Since your eyes are extra sensitive to that wavelength of light, newer fire trucks are being panted that color so they’ll stand out. Awful color, but it sure is noticeable.
You may have heard terms like “Red Dwarf” before. Now you should be able to get an idea of where these come from. They’re positions on this diagram. A red dwarf would be a red star towards the lower right. “White Dwarves” would be ones that were closer to the blue end, but still very small.
So let’s take another look at the HR diagram with those features plotted as well.
Again, pay no attention to the x-axis where it speaks of Spectral Class. I’ll explain that when I start getting into chemical composition and the spectra of stars.
But here we can see more clearly how size and color progress, as well as how a few popular stars like Betelgeuse, Sirius, Vega, and others stack up.
But not pictured on here, and still not discussed is one more important feature that we can plot: Mass.
To figure out how that would figure in, let’s stop to consider why stars are, well, stars. Even without taking a hunch of courses in astronomy, you’re probably well aware that stars are accumulations of (mostly) hydrogen gas that’s hot enough to undergo nuclear fusion in its core. But why are they so hot?
The reason has to do with where they come from. Stars (and their respective solar systems) start off as giant clouds of gas, lightyears across. Eventually, the cloud collapses under its own gravity. Bur remember how I discussed gravitational potential energy when talking about electron orbitals? The cloud has a net potential energy as well.
As everything collapses from something light years across to only a few million miles, there is a huge release of that potential energy. It is converted (at least in part) to heat.
So where does mass factor in to all of this? The answer is that the more mass there is, the more gravitational potential energy it has. Thus, more mass leads to more energy converted to heat, which means higher temperature! Cutting out the middle steps, and reversing it, hot stars are more massive.
I couldn’t find an image with this plotted on it, so I’ll just let you use your imagination.
So that’s an introduction to the HR diagram. By finding a star’s temperature (which is synonymous with color and something called spectral class), and its luminosity, we can figure out the mass and the size!
Suddenly this two for one post deal became a 4 for 1. Not bad.
Since the HR diagram we looked at today was generated by the closest stars, next time I post on the topic of how we learn things in astronomy, I’ll talk about a difference in these for when we look at stars in clusters. This difference gives us another important feature of the stars in that cluster: Age.
I’ll probably get that up in a few days since tomorrow’s Monday and I’ll be heading back to work on research, meaning I won’t have as much free time.
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