Tuesday, April 29, 2008

The Intro To Astronomy Series

For those that haven't followed this blog for a long time, one of the things you may very well have missed is that back when I started, I had a series of posts about the basics of how astronomy learns what it does. It started off with a look at where the light we look at comes from, and then discussed the difficulties it has getting to us, how we detect it, and finally, how we learn things from it. I stopped added to it back in the summer of 2006 because I didn't feel there was much more to add on that really fundamental level, but I noticed today when I was planning to write up something about my current research that there are a few topics that I never explained so I intend to do a bit more on that series.

But for those that haven't seen it before, here's the list of posts in my Intro To Astronomy series. I'll keep this updated and put a link in the side bar to act as a standard reference.

Data Acquisition and Analysis
1a. What is Light?
1b. Where Does Light Come From?
2a. Reddening, Absorption, and Extinction
2b. Light Detection
2c. Image Calibration
2d. Astrophotography
3a. The H-R Diagram
3b. Main Sequence Turnoff of clusters to determine age
3c. Spectroscopy
3d. Radial Velocity
3e - 1. Photometry Basics
3e - 2. More Photometry

Stellar Evolution
The Big Picture
Evolutionary Tracks
The Effects of Convection
Variables and Asteroseismology
The Synthesis of Elements in Stars
Making Nickel
Makind Dust
Hidden Creation

Spiral Structure
The M81 group
Galactic Evolution

Tuesday, April 22, 2008

Book Review: God is Not Great

Yeah, yeah. I know God is Not Great (Christoper Hitchens) wasn't the next book on my reading list but I found an audiobook of it cheap and it's a lot easier to listen to something walking to campus and back than it is to read (unless I want to wander into oncoming traffic).

So listening to an audiobook was new to me. It's a very different experience and I'm not all together sure how much it affects the perception of I have of the book, so I'll pretend it didn't in any large way.

Anyway, contrary to what you'll probably expect, I ended up finding God is Not Great to be a pretty worthless book. Perhaps it was the experience of listening to an audiobook, but I didn't find a single passage that was noteworthy enough to quote (which if you've paid attention to my other reviews is a startling exception).

The book started off well enough. It introduced the danger religion poses: Encouraging people to do downright stupid things due to a lack of critical thought under the guise of "faith". And worse, the disasters it causes are supposed to be tolerated. The best example given was a Jew performing circumcisions followed the instructions given in the Torah which calls for the foreskin to be bitten off. In the process of doing this, the practitioner passed along herpes to the children he was circumcising. One died and another suffered brain damage. Was this in a backwater village? No. Modern day New York. And instead of protesting this act, the mayor called for it to be respected. Another of the early chapters looked at how some religious beliefs are just plain stupid. Namely, this chapter focused on the demonization of the pig of some religions.

Salman Rushdie's plight was another major point that Hitchens made that was particularly good. Rushdie, whose fiction novel, The Satanic Verses sparked outrage in the Muslim community has had death threats and even attempted assassinations leveled at him due to a fatwa issued. As with the herpes transmission before, instead of condemning this, many instead blamed the victim thinking the order to murder over a work of fiction as something that was somehow inherently worthy of respect because it was religious.

The argument against the nonsense that religion makes people behave better was addressed very well, showing that many of the figureheads of the better behaving religious weren't really all that great. For example, Ghandi may have been kindly, but tried to (and in some manners succeeded to) drag a country down into a new dark age after secular powers had worked to gain independence.

In anticipation of the reverse of that argument, Hitchens attempts to address the other side of that coin: Atheism makes bad people (a particular favorite of the trolls here), pointing the finger squarely at Stalin, Pot Pol and Lenin. Hitchens' response was not at all convincing. The short version is that those that are often pointed to have little to do with what we typically consider atheists, meaning people who stick to a material philosophy and rule out the supernatural. Rather, they built themselves and their empires into their own gods, supplanting religious ideas with nonsense like Lysenkoism. As such, they had more in common with the religious counterparts than typical atheists. What Hitchens manages to miss however, is the more fundamental point: None of them every claimed to undertake their programs because of their atheism. Thus, trying to point to that as a cause is as rational as pointing to the fact that they were all white men. The same can not be said for their religious counterparts. So it seemed to me that Hitchens fumbled a strong argument there.

But aside from these few highlight, the book took a serious turn for the worse. The supporting arguments tended more towards personal testimonies which were rather ineffective and not suited for the grand generalizations Hitchens often drew from them. The main argument of chapters often became hopelessly lost in the rambling narratives Hitchens digressed into. The argument that the "miracles" espoused by religion is the equivalent of parlor tricks when compared to that which science has brought forth was cute, but not especially convincing.

Overall, out of 19 chapters, only five or six were particularly interesting and even then, only in parts. After "reading" this book, it seems strange that theists should get so upset about it given that it's not even that good.

Tuesday, April 15, 2008

The Use of Nanoparticle Coated Liquid Mirrors for Astronomical Use on the Moon

ResearchBlogging.orgThe development of telescope technology has been a long process. In recent years, most large single mirrors for telescopes have been based on the traditional design of a glass base, shaped into a concave parabola, coated with a reflecting surface (typically aluminum) deposited in a evacuated vaporization chamber. The parabolic shape is often obtained by beginning with a liquid glass which is placed into a mold and spun as the glass is allowed to cool. The balance of the centrifugal and gravitational forces creates a parabola, the depth of which (and hence the focal length of the telescope) can be controlled through the rotation speed.

The major disadvantage to this design is that the glass mirror becomes excessively heavy and is unable to support its own weight well above a radius of eight to ten meters. As such, new techniques have been developed that use segmented mirrors. Another novel technique that is currently beginning to see use is that of using liquid mirrors that do not solidify. This practice has already been put into use with the Large Zenith Telescope which boasts a 6m diameter liquid mercury mirror.

Unfortunately, mercury and most other highly reflective liquids are prohibitive due to their toxic and/or unstable natures. Additionally, with the current drive to establish new locations for possible observatories, such mirrors would be required to function in new environments. One of these proposed environments would be a possible moon base. In such a case, traditional glass mirrors would be impossible, due to the high cost of transportation. Thus, a liquid mirror becomes much more practical, if an appropriate liquid can be found.

The requirements for such a moon based mirror would be that they have extremely low freezing temperatures and retain their liquid state in vacuum as well as be non-toxic and stable. Although a number of possible candidates exist, few have an intrinsically reflective nature, although Burns (2008) reports that Lithium Ammonia may be suitable. This requires that such a material be coated with a reflective surface.

Finding suitable materials that fit these criteria and attempting to coat them was the subject of a 2007 Nature paper by Borra et al. In addition to the restrictions placed on a possible telescope by the inhospitable lunar conditions, the coating process also adds additional constraints in that the coating must be smooth enough, and reflective enough to serve as a functional mirror in the desired wavelength range (infrared in this case).

Since coating of liquid surfaces had not yet been attempted, the researchers attempted to coat several different materials using a vaporization deposition resulting in films only a few nm thick. Most of these attempted coatings were unsuccessful. From this, they further refined their liquid criteria to require the liquid to have nearly zero vapor pressure and high viscosity. The ideal class of compounds they determined to be ionic liquids which are salts in liquid form at low temperatures (defined as below 373 K). The challenge was then to apply a silver coating in order to make a suitably reflective surface.

Fig 1. - Reflectivity curves for various silver coated liquids. PEG curve is shown for an attempted liquid deemed not suitable and not discussed in this post. As discussed in the paper, the most promising is the ionic liquid with an initial chromium layer (5nm) followed by a 30nm silver coating. Curves only extend to 2.2 μm due to instrumentation limitations. (Borra 2007) .

To do this, Borra et al. applied a thin film of silver nanoparticles to the surface with diameters of only a few tens of nanometers. However, the nanoparticles tended to diffuse into the liquid substrate forming a colloid, reducing reflectivity with respect to metallic silver. In order to mitigate this problem, the group first applied a chromium layer. This layer tended to bond easier and form a better surface to which the silver could then be applied. With this additional coating, Borra et al. were able to increase the reflectivity as shown in Figure 1.

Although reflectivity is as high as 80% for some wavelengths, Borra notes that this is still low for standard astronomical mirrors which often have reflectivity over 95%. In an earlier paper (Borra, 2004), it was noted that these surfaces would often begin with a higher reflectivity, which would decrease over the course of a week by ~8% and remain relatively constant thereafter. They surmise that greater stability and reflectivity may be reached with different metallic nano-coatings. Borra did not note whether or not the chromium backed silver coating had the same degradation as previously mentioned.

Aside from just being able to reflect incoming light, mirrors would also be required to have a suitably smooth surface that they would produce high quality images. To analyze this, the group mapped the topographical distribution via electron microscopy, of the produced surface (with a 5nm chromium layer and a 30 nm silver coating) and found it had a peak to valley depth of 0.0373 µm which gives an excellent optical surface (see Figure 2).

Fig 2. - Three-dimensional map of a 1.25 cm2 section of the 5nm chromium/30nm silver mirror deposited on an ionic substrate. Peak to valley distribution is 0.0373 μm. (Borra 2007)

In the 2004 paper, Borra also describes the possibility that mirrors could be further shaped with the application of magnetic fields, if the mirror’s substrate was composed for ferromagnetic liquid. Although it would not be necessary in the lunar vacuum, controlled deformations have been used on telescopes to correct for atmospheric aberrations. This technique is known as adaptive optics.

However, the liquid mirror technique is not entirely without drawbacks. One of the most obvious is that the mirror must remain horizontal. Tilting the mirror’s axis would cause deformation in the topography, rendering the surface unusable for observations. In other words, the mirror must be permanently fixed on the observer’s zenith. However, telescopes such as the famous Arecibo, are also zenith based and function quite well for their particular sorts of observations. Namely, this liquid mirror telescope would be quite well suited for deep field imaging since, at large distances, a greater volume of space is shown. But to do imaging of such distant objects, exposures must be taken for a longer time. Since the telescope would be turning with the moon, this would limit the total exposure time as the object swept over the field of view. As such, several images would have to be taken and subsequently added to produce a suitably deep image. Again, on the moon, this would be less of a problem since the moon has a slow rotation rate (~28 days), allowing objects to stay in the field of view for longer times.

Although not discussed, another problem I could foresee would be a possible interruption of power. If power to the rotator would be lost, the centrifugal force would vanish, and the liquid substrate would settle back into a flattened shape. Most likely, this would result in a tearing of the nano-coating, causing the mirror to need to be entirely recoated. If the liquid were viscous enough, short power interruptions may be mitigated. Regardless, this may not be as large of a problem as it may otherwise seem, since telescope mirrors are frequently resurfaced as it is, in order to retain a fresh and dust-free surface.

Fig 2. - Reflectivity of Li(NH3)4. Measured points from McKnight and Thompson (1975) at 195 K. Theoretical curve is shown for 93 K. (Burns 2008)

Overall, the work of Borra et al. has clearly shown that there is a great deal of promise in the formation of mirrors using nano-coated ionic liquids. Even in these initial tests, they have been able to achieve surfaces which are smooth enough to make excellent surfaces. Although the surfaces are not yet reflective enough to meet the standards for astronomical instrumentation, it is likely that with further experimentation with different coatings as well as additional intermediate substrates, it is likely that this can be greatly improved. Yet while the concept has been well established, the question remains whether or not this is the most economic or feasible option for a liquid mirror. As Burns suggest, it is likely that there exist other materials that have similarly high reflectivity and would not suffer from the drawback of requiring an additional coating. For example, the liquid lithium ammonia mirror they recommend has reflectivity curves similar in quality to that of these more complicated, coated mirrors of Borra (see Figure 3).

As such, although the concept is sound, it would seem that further development and testing will be necessary before it can be determined which sort of mirror would be best for use in a lunar environment.

Borra, E.F., Seddiki, O., Angel, R., Eisenstein, D., Hickson, P., Seddon, K.R., Worden, S.P. (2007). Deposition of metal films on an ionic liquid as a basis for a lunar telescope. Nature, 447(7147), 979-981. DOI: 10.1038/nature05909

Borra, E.F., Ritcey, A.M., Bergamasco, R., Laird, P., Gingras, J., Dallaire, M., Da Silva, L., Yockell-Lelievre, H. (2004). Nanoengineered astronomical optics. Astronomy and Astrophysics, 419(2), 777-782. DOI: 10.1051/0004-6361:20034474

Burns, C.A. (2008). Is Lithium Ammonia Suitable for a Liquid Lunar Telescope?. Publications of the Astronomical Society of the Pacific, 120(864), 188-190. DOI: 10.1086/526539

McKnight, W. H., & Thompson, J. C. 1975, J. Phys. Chem., 79, 2984

Monday, April 14, 2008

Mother Murders Sleepwalking Daughter

Many times on this blog I've reported on how things that should in no way be dangerous, when combined with religious inanity, can suddenly become a life threatening situation for people involved. As Hitchens put it, "Religion poisons everything"; From exorcisms for every day behavior and illnesses, to drinking sewage, to staring at the sun.

And yet again, we have another story of a parent murdering their child because of religion. As sad as this is, I have long since lost surprise at the amazing things people will do when their minds have been corrupted by religion to the point that rational thinking is no longer possible.

In this case, a mother stabbed her daughter. Eleven times.

The mother originally claimed this was in "self defense" when her daughter came at her with a knife. But it's quite apparent that even after disarming the six year old the mother then proceeded to attack her, going far beyond what can be considered self defense.

The real cause? The daughter was sleepwalking. After conferring with a superstitious relative, the mother decided the child was possessed by a demon.

Sunday, April 13, 2008

MARAC 2008 Review

Well, the MARAC meeting is over. There's some highlights, some low lights, and since several talks were done with no lights (aside from the projector) there was some nap time too.

Unfortunately, I had to miss the first two sessions due to my Nanotechnology class, which is a shame, because some of the talks seemed pretty interesting. Josh Tartar from Mizzou, laid out the background for the larger framework which he, his adviser (Angela Speck) and another grad student (Adrian Corman) have been working on involving some really interesting stars. These stars do the typical thing that most post main sequence stars do as they die; They puff up and slowly shed their outer layers in soft puffs of material.

But the thing that's really cool about these stars is that they're at the very end of this asymptotic giant branch phase and doing some serious dredgins up of the carbon interior and losing the very last layers at a frenzied pace. The effect of this is that over a relatively short amount of time (tens of thousands of years short), the entire star becomes enveloped in shell of it's own making so optically thick (due to dust grains and heavy molecules forming out of the fresh material) that the star itself is no longer visible! The work that these guys are doing (which I got to catch up on through the later talks and chatting with Josh at dinner). Essentially, they're taking the spectra from these shells, and using a program to try to recreate the observed spectra.

This is a lot harder than it sounds because there's a lot of variables: composition, size, temperature, optical depth... Some of those can be observed somewhat and fixed, but there's too many to completely say so it takes a lot of playing around with. And to make things worse, the solutions can become degenerate. In other words, two sets of parameters may return the same spectra. Sometimes they can be ruled out as possible (such as one which returns the temperature as higher than is realistically possible), but other times, it's harder to do. Regardless, it's an interesting project and Angela had purple and black hair with a hot accent so all the more fun there.

Another talk I missed came from James Roe of the Astronomical Society of Eastern Missouri letting everyone know that they have their new observatory up and running that has the equipment to do some basic photometry and they're willing to do some of the routine monitoring for others whenever possible.

The first talk I saw from someone at KU was one from John Ralston. The only time I've really had to deal with him here was when he subbed in my Quantum class one day while the normal professor was at a conference. Essentially he told us to ignore everything we'd learned because none of it was pretty in theory and h-har equals 1. Ralston is a theorist.

Anyway, he has a tendency to make his slides using the Mac equivalent of Paint, so they're brightly colored to the point of being garish, and impossible to read. Since I'm not a theory person I tuned out for most of the talk, but the main message was that Dark Energy doesn't appear to be uniformly distributed.

The next talk was by another KU professor: Danny Marfatia. I didn't intentionally tune out on this talk, but he has a tendency to start off his sentences in a nice strong voice and trail off into mumbling, so I didn't really follow much of what he was going for. Only that the fine structure constant, α, may be varying over the history of the universe, but if so, then only very weakly and not in any terribly important way (sorry to get your hopes up Creationists).

The first talk of Saturday was from Steve Black from Washburn University and was probably one of the worst talks I've ever seen given. The entire talk was about being able to observe stars as they were occulted by the moon. Typically, if you want to do good photometry, you need to do this when the moon is still pretty new so the glow from the moon doesn't wash out the star. But by observing in the IR, you can do observations until first quarter.

That's all and good, but what does that tell us? Protip: If you want to have people care about your talk, tell them what's important about it.

The next talk was on dynamic bar mode instabilities in neutron stars by Karen Camarda from Washburn as well. I'd heard this talk a week or two back so I took a nap for this one, but the idea is that, as neutron stars rotate, the instabilities can cause the star to collapse, not to a point, but into a bar. At least temporarily. Not terribly exciting in and of itself, but these quick collapses would make strong distortions in space time and should be able to generate the highly sought after gravitational waves. Since neutron stars are more common and closer than many other things that could do this, this may be our best bet at detecting gravitational waves.

The single best talk came from Todd Boroson, the interim director of the National Optical Astronomy Observatory. Recently, the NSF (which funds NOAO) did a review of the program trying to look at how effective they were being. The result was that the NOAO was "moving too fast". Too much investment was being made on large telescopes and not enough on smaller, workhorse ones. Unfortunately, there's a bit of a catch 22 with that. The NOAO hasn't been spending money on these telescopes because astronomers haven't been applying for time on them (the 2.1m was underbooked recently). Astronomers haven't been applying for time on them because the equipment isn't up to par because the NOAO hasn't been spending money on them.

So they've launched a new program called Renewing Small Telesopes for Astronomical Research (ReSTAR). Of course, they also intend to keep working on getting more time on major observatories like Keck and Gemini as well as investing in new projects. Additionally, they're looking at starting classes which would teach observational techniques at these nationally funded observatories to allow students to get experience they couldn't get at smaller universities that don't have strong research programs.

Brenda Culbertson gave a talk on the use of the planetarium at her school. It wasn't all that novel or exciting. It essentially amounted to "Planetariums are cool and kids say it helps them understand things better." Duh.

Christoper Sidell and Kevin Lee from University of Nebraska gave two talks on some new classroom software they've been working on. The first was a new lab on variable star photometry. I really liked this and wish I could use it in my lab. Unfortunately, it's a bit over the heads of my students since it doesn't really cut many corners. It simplifies a few things, but it really shows all the steps you have to go through in real astronomical data processing: From correcting images for noise, to aligning them, to getting the data.... An excellent lab that I probably will try to water down a bit and use for my classes sometime in the future.

Their other program is called Class Action and is an in class teaching program that covers major topics in astronomy. It's designed to allow for real time feedback in the classroom. It features quizzes that can be approached from several different angles so it's not quite so routine, and in case the students get stuck, it also has tools with some really fun animations and tools to help explain the topic.

Paul Temple from one of the local astronomy groups gave a quick talk on the possibility of using RGB cameras (essentially expensive webcams) for actual astronomical research. The filter systems aren't all that close, so standardization would be shot, but it's not too far off in the green (V/G) filter. At the very least, they can allow for eclipse timing. Paul was going to report on how close he could get on standard stars, but due to a hard drive crash, was unable to put that together in time.

The next invited talk was from Eric Linton of Benedictine College talking about using Cerenkov radiation for use in observing extremely high energy gamma rays. Since gamma rays can't make it through our atmospheres and space based telescopes are expensive, astronomers need another way to observe this spectral regime. As gamma rays enter out atmosphere, they suddenly find themselves traveling faster than the speed of light in the local medium and make a shower of all sorts of crazy particles. By detecting these particles, you can start to reconstruct the image presented by the actual gamma rays.

According to Brian Thomas from Washburn, the famous supernova to be, Eta Carine, isn't a threat to us. Even if it were as bright as the superluminous 2006gy, it's still too far away to be felt much. Even increasing it by 1000 times that, it still would barely dent our atmosphere. The novel bit of this research was asking what the effect would be on our endocrine system. The endocrine system is partly our internal clock, so if Eta Carine blew and suddenly it was bright all night too, that might screw with things a bit. And since the endocrine system also controls the immune system, that's a bit worrysome. But the predictions say that at that distance with the expected size of supernova Eta Car will produce (which will be damn big) it still won't be much more than -7 apparent magnitude. Bright enough to see during the day, but still far fainter than the full moon. So nothing to worry about.

Baker University's Ran Sivron talked about modeling the accretion disks of black holes and how energy propagates through it as a means to determine (or at least place constraints on) the mass of the central object. It looks like some of these black holes may be 3x less massive than previously thought. But what was really cool about this project is that it was, in large part, done by high school seniors! Way to show 'em how cool astronomy is!

Jeff Wilkerson from Luther College talked about looking for short-period variable in open clusters. Jeff had talked about the same topic at MARAC last year. His program is really just a gigantic crap ton of data collecting. On any night when it's clear, he and his students head to the meager observatory his school has, and just shoot image after image of the clusters he's observing. In the past decade, he's collected nearly half a million images. The trick is sorting through all this mess, trying to find the interesting stars out of the hundreds or thousands in each cluster. That was the focus of this talk, in which he described how to try to find these stars using how much they had to be normalized to get each frame to have the same standard system.

The last talk was given by Scott Baird from Benedictine in which he described the effect of reddening on metalicity estimates in the Small Magellenic Cloud. The short version was that, even using some fairly significant different reddening amounts, the metalicity didn't change enough to be outside the error in it that comes from the inherent error in photometry. In other words, it's not that important at this level.

So that's the MARAC conference. Now excuse me while I get back to writing the three different talks I have to give in a week.

Friday, April 11, 2008

MARAC 2008

I'm off to the 2008 MARAC meeting in KC! Yay astrophysics!

Hopefully there will be some fun talks this year I'll have something to say about.

Tuesday, April 08, 2008

Gratz to the Jayhaws Basetball Team

I'm not much of a sports fan, but since it's a rather big deal around here, congrats to the Jayhawks basketball team which won 75-68 against Memphis in overtime last night, to get their first national championship since 1988.

Rock Chalk, Jayhawk, KU!"


In Philly, Salem, and now Britain, psychics are having a hard time.

In a new British Law, it will now be the job of "the medium, to prove they did not mislead, coerce or take advantage of any 'vulnerable' consumers." The law will require them to add disclaimers noting that their trade isn't guaranteed to work (Duh!).

Predictably, psychics are whining about having to actually take responsibility for what they sell. According to the article,
Carole McEntee-Taylor, a spiritualist healer in Essex, said having to stand up and describe the invoking of spirits as an [scientific] 'experiment' was forcing spiritualists to 'lie and deny our beliefs'. She added: 'No other religion has to do that.'
Well Carole, what other religions sell themselves offering phony and useless services (oh yeah, besides these frauds)?

But I will agree with them that it's not a scientific experiment when you refuse to look at the results and see just how poorly you do.

Monday, April 07, 2008

Flare Research: Onwards!

I've previously mentioned that my project into super flares on solar type stars was at a bit of a temporary dead end because my first and main approach to the topic (to see if planets had any effect on their stars chromospheres) had already been answered and the other direct approach (looking for planets around these stars) is being done by someone else.

So what's next?

The next obvious question is whether or not any of these systems with known close-in planets have flared. But unlike everything else I've been doing so far, this isn't just a case of trying to go through the literature and see what comes up. Instead, we'll be doing the data analysis ourselves.

Which means we need data.

The first source for lots of data would be from some of the big sky surveys. Only trouble with that is that, since it takes deep exposures, many brighter stars, namely the ones that are likely to have planets found around them, will be overexposed for those stars, and we can't really do any honest data analysis on them. But even for the stars that might work, I still need to get a tutorial on how to use IRAF's aperture photometry mode as opposed to the profile-fit that I did in San Diego.

So that means we may need to be taking our own data. Which means writing proposals for telescope time. Exciting, huh?

FSM statue graces courhouse lawn

In an amazing rarity, a courthouse in Cumberland, TN has created a free speech zone on its lawn in which members of the community can file to have statues and monuments erected on its lawn. Obviously, there's the typical Christian references with a chainsaw carving of Jesus carrying a cross, but amazingly enough, this town actually does allow for other monuments, and has allowed a Flying Spaghetti Monster one to be put up as well!

Of course, what would be it without some politician acting butthurt over the whole thing,
I feel the Flying Spaghetti Monster is an effort on the part of non-Christians to try and minimize Christianity and the images that have been placed there. I'll go as far as to say that I think it's an attempt to minimize and ridicule the good intentions of Christians in Cumberland County...
That's right... The FSM is out to minimize your monopoly.

He's coming for you....