The Evolution of Stars - stars evolve in stages over billions of years 1.Nebula -interstellar clouds of gas and dust undergo gravitational collapse and rotate forming a protostar -increased pressure causes the temperature of the gas to rise and become plasma -process of nuclear fusion takes place at 10,000,000 o C forming a star

Nebula

The Evolution of Stars 2.Main Sequence Stars -the stage of life where a star is fusing hydrogen into helium in its core -approximately 95% of all known stars (including our Sun) are in this stage

The Evolution of Stars 3.Red Giants and Supergiants -form once stars have fused all the hydrogen in their cores into helium -helium then fuses into heavier elements such as carbon and oxygen -it then expands and cools to become over 100 times the size of our Sun

The Evolution of Stars 4.The final stage in the life of a star is dependant on its birth mass: Below five solar masses White Dwarf: remaining matter into a hot, dense core surrounded by a planetary nebula

The Evolution of Stars Above five solar masses Supernova: violent explosion forming either a black hole (a region of space where gravity is so dense that even light cannot be emitted) or a neutron star