Summary I
The Universe around us
- Our sun and solar system is a small part of the Milky Way
- Milky Way: A spiral galaxy of ~ 200,000,000,000 stars (2 x 1011)
- Almost all the stars we see are in the Milky Way
- Billions and billions of other galaxies visible with telescopes
Galaxies and stars form from gases (mainly H) pulled together by gravity
- Stars produce energy from Nuclear fuel
Death of a star
- Supernova! Release more energy than a galaxy (for months) All heavy elements formed in supernova!
- Remnant of Collapse:
- Small stars becomes brown dwarfs
- Larger (like our sun) become white dwarfs
- Mass > 1.3 sum mass: neutron star (pulsar)
- Mass > 1.5 sun mass: black hole