Poor in one, Rich in another

Tycho's Supernova Remnant. Credit: Spitzer, Chandra and Calar Alto Telescopes.

Just over three years ago, I wrote a blog post commemorating the 50^th anniversary of one of the most notable papers in the history of astronomy. In this paper, Burbidge, Burbidge, Fowler, and Hoyle laid out the groundwork for our understanding of how the universe builds up heavy elements.

The short version of the story is that there are two main processes identified: The slow (s) process and the rapid (r) process. The s-process is the one we often think about in which atoms are slowly bombarded with protons and neutrons, building up their atomic mass. But as the paper pointed out, this often happens too slowly to pass roadblocks to this process posed by unstable isotopes which don’t last long enough to catch another one before falling back down to lower atomic number. In this case, the r-process is needed in which the flux of nucleons is much higher in order to overcome the barrier.

The combination of these two processes has done remarkably well in matching observations of what we see in the universe at large. But astronomers can never rest easily. The universe always has its oddities. One example is stars with very odd relative amounts of the elements built up by these processes. Since the s-process is far more common, they’re what we should see primarily, but in some stars, such as SDSS J2357-0052, there exists an exceptionally high concentration of the rare r-process elements. A recent paper explores this elemental enigma.(...)
Read the rest of Poor in one, Rich in another (426 words)

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© jvois for Universe Today, 2010. | Permalink | 6 comments | Add to del.icio.us
Post tags: metals, stellar evolution, Supernovae

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