September 22nd, 2022

Big Bang to Humankind

  • The stars that create elements are off the main sequence (the ones on the main sequence are making helium).
  • A galaxy with blue stars is actively forming new stars, because they’re hotter and newer.
  • Oxygen is the most abundant element in the Earth.
  • How planets form:
    • A supernova forms lots of cloud and dust
    • Planets pick up mass like a snowball
    • Solar winds (of gasses) blow away other dust
  • The solar system is 74% hydrogen, 24% helium, and 2% everything else.
  • Densities of common objects:
    • Iron: 7.9 g/cm^3
    • Water: 1 g/cm^3
    • Ice: 0.9 g/cm^3
    • Rocks: ~3 g/cm^3
  • Terrestrial worlds:worlds we can stand on (like the 4 inner planets).
  • Frost line: 3 AU
    • Inside the frost line, planets form out of only rock and iron (water vaporizes)
    • Outside the frost line, planets form out of rock, iron, and ice
  • Denser things vaporize and condense at higher temperatures