1. Stars

2. The Sun
1 A.U. (Astronomical Unit) = average distance from the sun to Earth.
The sun is a medium sized star called a yellow dwarf.
The sun contains 99% of the solar systems mass.

4. Why do stars shine?
Stars begin as enormous gas (hydrogen) and dust clouds (Nebula) that gravity condenses into a sphere.
Gravity crushes the gas in the center of the star causing a nuclear explosion. (fusion)
Greater mass = greater gravity.

6. A star’s life Stars fuse hydrogen into helium.
The explosion outwards is balanced by the inward pull of gravity. (equilibrium)
This state remains until all of the Hydrogen is used for fusion. (Main sequence star)

7. Stable stars (main sequence stars):
Very massive stars: very hot, glow white or blue, short life
Sun types stars – glow yellow or orange, long life

8. Stellar Life Cycle