Giants and Dwarfs with Barium

I’m beginning to think that a large fraction of the astronomical community is in pre-semester stars chaos. The number of press releases has radically slowed, and the journal articles just don’t seem to be flying as fast and furious as normal. Admittedly, this is a personal impression, and while I have data to support the number of press releases, it could simply be some wishful thinking that makes the number of papers seem fewer.

That said, what the papers lack it number, the make up for in titles. For instance, consider the following:

Ruthenium and hafnium abundances in giant and dwarf barium stars by D.M. Allen and G.F. Porto de Mello.

So imagine with me if you will: Before you expands a waiting room of sick dwarves and sicker giants who all happen to be movie stars. Some of them have had a bit to much Ruthi and others got into the hafnium before they all landed at the ER. Now some nice nurse has handed them a swig of barium to fill them up before they go in for testing.

This is what lept to my mind when I read that title.

All joking aside, this was a very serious paper that did some very difficult research. All very heavy elements – those heavier than lead – are produced during supernovae explosions. Some of these elements are produced by simply bombarding atomic nuclei with neutrons under extreme conditions. During a core-collapse supernova, the type created during the death of a single giant star, 10^22 neutrons per square centimeter can be emitted (that is a 1 followed by 22 zeros of neutrons flowing thru the area of a typical adult big toe toenail). With that many neutrons flowing, they will actually hit atomic nuclei at a rapid rate. When too many neutrons build up in just the right conditions, they decay into a proton, electron and neutrino.

This process can happen over and over as things build and decay at different rates as they constantly get bombarded. This process also has a slower cousin that takes place in stars that sometimes leads to low level production of heavy elements (a process that generally gets swept under the rug when discussing the creation of elements with the public).

Back in graduate school, while I spent a part of my life studying the isotopic ratios of Magnesium Hydride in stars, I had this fabulous chart that you could use to trace out the rapid neutron capture and other processes that can lead to different isotopes. It was a giant poster, and a quick google didn’t allow me to find it to share with you, but I did find this applet you can use to watch the growth and decay of elements. It lacks the excitement of a supernova blast, but it’s kind of neat none the less.

So, in making that poster I had and this applet I just shared, scientists spent countless hours calculating decays and atomic cross sections, and all sorts of crazy particle physics and quantum mechanical things. They think they’re right. We experimentalists think we can believe them, but… Well, data helps all of sleep at night. To prove them right stellar spectroscopists like Allen and de Mello have to pain stakingly measure the ratios of rare and hard to study elements in stars and test those ratios against theory. In this case, they were testing the ratios of the heavy element Ruthenium (made mostly but not entirely in the rapid process) and hafnium (which is made mostly but not entirely in the slow process). They found that while most of the time theory and experiment matched (woot!), there were several cases where these two elements where produced in stars (AGB stars to be exact) in higher levels than theory can explain.

This means the theories aren’t completely right yet, but they’re getting there. It means there are new projects for students, and new things to learn about stars and supernovae. But we’re getting there. We’re way more right than we are wrong.

This paper will never have a press release written about it. I only read it because its title made me think of sick giants and dwarves undergoing nasty medical procedures. None the less, this paper represents where the incremental advances in science are coming from. Slow and study, careful and thorough, building our understanding one isotopic abundance at a time.

One Comment

  1. chris August 17, 2007 at 12:48 am #

    The link to the applet is broken, you have a ” appended to the URL.

    Interesting post, though.

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