ASTRON 1101 Lecture Notes - Lecture 38: Cosmic Microwave Background, Planck Constant, Planck Time
6 Dec 2016
School
Department
Course
Professor
Document Summary
The sun formed more than 9 billion years (9 gyr) after the big bang. As a result, it contains recycled material (gas from an earlier generation of stars) The first stars formed < 0. 5 gyr after the big bang, and contained no recycled material. Look at the spectra of intergalactic gas clouds. When illuminated by background quasars, they produce absorption lines. Result: none of the early, pristine gas was less than 24% helium by mass (the rest is nearly all hydrogen) The first stars formed from gas that already contained helium. Where did this primordial helium come from: primordial = present before the first stars. Another result: the early gas contained trace amounts of lithium. There were about 3 grams of lithium for every 10,000 tons of hydrogen. Where did this primordial lithium come from: and why was there no beryllium or boron or carbon, etc.
