Knowing Our Cosmic Sperm Donor

In perusing the recent articles in the ApJ, one of the ones that caught my eye this week was one entitled, “²⁶Al and the Formation of the Solar System from a Molecular Cloud Contaminated by Wolf Rayet Winds”. Quite the mouthful to be sure, but it's an interesting paper.

The idea is that a number of unstable elements (specifically ²⁶Al) are present in the oldest of meteoritic materials in higher concentrations than would be expected if our solar system had simply formed from the gravitational collapse of the local interstellar cloud. Their presence indicates that some sort of event happened near our solar system which injected these elements as the cloud underwent its collapse.

In general, heavy elements like aluminum are cooked up in stars. In fact, the ratios of elements observed in these remnants suggest it wasn't just any star, but a massive star. But once those elements are cooked up, the next trick is transporting them to our fledgling solar system. But how?

One obvious answer is to blow up the star that's making the elements in a supernova and spread them all over the place. Another possibility was that the elements were blown here in a gentler manner from a type of star known as a Wolf Rayet star. These stars are massive stars that are so hot, they blow off their outer layers.

The trick is to determine which of these possibilities was the real deal. Again, the ratios tend to rule out supernovae as a possibility due to the fact that such an occurrence “invariably over-predict the abundance of ⁵³Mn”. To get the right abundances, the scenario that fit was that a nearby cluster of stars released the necessary elements as our solar system was forming, but while it was still dispersed enough to be vapor.

This paper really highlights one of the things I really love about astronomy and science in general; Small details, like the overabundances of rare materials in this case, can give hints at very grand questions, like where we came from. I find it amazing that we are capable of determining what our fore bearers must have been like even though they are no longer around just by looking at that which we carry inside our own solar systems and bodies.

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Gaidos, E., Krot, A., Williams, J., & Raymond, S. (2009).
Al AND THE FORMATION OF THE SOLAR SYSTEM FROM A MOLECULAR CLOUD CONTAMINATED BY WOLF-RAYET WINDS
The Astrophysical Journal, 696 (2), 1854-1863 DOI: 10.1088/0004-637X/696/2/1854