NS: Supernovae don't make the biggest atoms

Find out the latest thinking about our universe.
Post Reply
User avatar
bystander
Apathetic Retiree
Posts: 21571
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

NS: Supernovae don't make the biggest atoms

Post by bystander » Sat Jul 03, 2010 4:48 am

Supernovae don't make the biggest atoms
New Scientist | Physics & Math | 02 July 2010
THEY are the brightest of stars, but supernovae may not forge the heaviest elements. That's the suggestion arising from analysis of a new model of the particle winds that rush from the cores of supernovae.

The only two elements formed in abundance shortly after the big bang were hydrogen and helium. All the heavier ones must have been forged by fusing these smaller nuclei together. The high pressures and temperatures inside ordinary stars can account for elements up to a certain size, but making elements bigger than iron, which has a nucleus containing 26 protons, requires some other mechanism.

That's where supernovae come in. These exploding stars blast neutrinos from their cores to their surface at close to the speed of light, kicking protons and neutrons out of other atoms as they go. This creates a "wind" within which neutrons and protons fuse to form the nuclei of small atoms. Further protons, neutrons and atoms join in to make larger ones.

But atoms larger than nickel, with 28 protons, won't accept new protons as the mutual repulsion of so many positively charged particles becomes too strong. To make these atoms, neutrons must enter the nucleus and then transform into protons once inside, a process known as rapid neutron capture or r-process.

It was assumed that all the heavy elements could be made in this way. Now Thomas Janka of the Max Planck Institute for Astrophysics in Garching, Germany, and colleagues say the composition of the neutrino-driven wind means it won't work for the largest elements.
Neutrino Signal of Electron-Capture Supernovae from Core Collapse to Cooling

Post Reply