Notes+on+origin+of+solar+system

toc =15.2 Origin of the Solar System=
 * 1) [|Stars] - balls of hot gas that emit light and other radiation
 * 2) [|Galaxy] - billions of stars (our galaxy is the [|Milky Way] with 400 billion stars)
 * 3) [|Universe] - billions of galaxies


 * [|Nebula] - area in space made from hydrogen (H) and helium (He) where stars form
 * [|Planetary systems] are stars with non-stellar objects (planets, moons, etc.) orbiting around them. The [|solar system] is a planetary system.

Formation of a solar system
1. __Star__:
 * gases come together (gravity)
 * balls of matter get so big they start to make light and radiation
 * "solar winds" from the new star blow away gases nearby away to the far reaches of a solar system

2. __Terrestrial planets__: Mercury, Venus, Earth, Mars
 * solid matter was not blown away by the solar winds
 * attract other matter to become bigger
 * terrestrial planets are cool

3. __Gas giant planets__: Jupiter, Saturn, Uranus, Neptune
 * form like stars but much cooler
 * found far away from stars

Planets and other minor objects revolving (orbiting) around a star form a [|planetary system].