Stellar EvolutionWhat is the fate of the sun

and other stars??

Formation of Stars• Begins with interstellar gas and dust called

a nebula• Collapses on self as a result of gravity• Rotates and flattens with hot condensed

object at center called a protostar

• When temperature becomes hot enough for nuclear fusion to occur Hydrogen (H) and Helium (He) are the first reaction.

Lifecycle of a Medium Star

• 10 % of a stars innermost mass react in nuclear fusion

• When H in core is gone, some left in outer layers

• Outer layers expand and cool; star becomes a Red Giant

• Red giants have low surface gravity, outer layers are driven away

• Core becomes hot enough to produce Carbon (C)

• Star contracts to normal size when helium is used up

• Carbon core left over, White dwarf remains

Lifecycle of Massive Stars• Massive stars undergo many reactions and

produce many elements• Cannot support themselves and violently

collapse on themselves

• Neutron Star – Collapse dense core of a star that forms quickly while its outer layers are falling inward

• Supernova – Massive explosion that occurs when the outer layer of a star are blown off

• Black Hole – Small, extremely dense remnant of a star whose gravity is so immense that even light can not escape its gravity field