ASTR 1102 Lecture : Lecture23
Document Summary
Core collapse is so rapid it bounces back out a bit. This sends out shock-wave (like sonic boom) This may drive off outer envelope of star in supernova. At shock, densities and temperatures high enough to fuse iron to heavier elements (absorbs energy from shock) Everything heavier than iron produced in supernovae - copper, lead, gold . Heavier elements all have more mass per nuclear particle. This does not fade as fast as it should. After a few weeks, energy is provided by radioactivity. Many are unstable (radioactive) and decay by nuclear fission. Keeps supernova bright for about a year. Envelope of star ejected at 1000"s of km/s. Expands out, and collides with previous ejecta or interstellar medium. Collisions heat gas to extreme temperatures (millions of degrees) Supernova remnants visible in x-rays (very hot gas) Also optical emission lines (hot, thin, transparent gas) Discovered by yang wei-t"e, imperial astronomer of the chinese court.
