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Stellar Evolution
What 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.
• A star is born.
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