The Life Cycle of Stars

Question	Answer
1	Nebula - a cloud of gas that forms a star.
2	Protostar - a cloud of gas becomes so compressed that the heat makes it glow. It then forms a protostar.
3	Main sequence - hydrogen nuclei get close enough to undergo nuclear fusion. Star can now stay stable for billions of years.
4a- Massive stars	Red supergiants - stars run out of hydrogen. Outward pressure doesn't balance gravitational pull. The stars core collapses, outer layers expand.
5a- Massive stars	Supernova - at the end of the red supergiant's life they collapse rapidly and then explode. Outer layers of gas are thrown off while the core continues to collapse.
6aa- most massive stars	Black holes - gravity pulls the cores of massive stars together to form black holes. Black holes are so dense that light can't even escape them.
6ab- massive stars	Neutron star - if remains are not dense enough to form black holes, a small, very dense, neutron star is formed.
4b	Red giants- - stars run out of hydrogen. Outward pressure does balance gravitational pull. The stars core collapses, outer layers expand.
5b	White dwarf- when the core collapses it forms a white dwarf. No more fusion can take place, the star gradually cools over billions of years.

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	Created by 12ha2609 almost 9 years ago