AST101H1 Chapter 1: AST101 - Chapter 1 Study Notes

• School: UTSG
• Department: Astronomy & Astrophysics
• Course: AST101H1
• Professor: Michael Reid

Document Summary

Average distance between galaxies are increasing, but individual galaxies (and planets and stars) occupy regions where gravity has won out against the overall expansion and do not expand. Point where expansion began (the big bang 14 billion years ago, estimated by rate of expansion) Massive stars die in titanic explosions called supernovae. Early universe contained only the simplest chemical elements: hydrogen and helium (and a trace of lithium) 2% may sound small, but it made the small rocky planets of our solar system, including earth. Star: a large, glowing ball of gas that generates heat and light through nuclear fusion in its core. Planet: a moderately large object that orbits a star and shines primarily by reflecting light from its star. An object can be considered a planet only if it: orbits a star is large enough for its own gravity to make it round, has cleared most other objects from its orbital path.