Transcript Lives of Stars PPT

Lives of Stars
Section 3
Nebula
• Large cloud of gas and dust spread out in an
immense volume
• All stars are born in a nebula, large cloud of
gas and dust.
Protostar
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Gas and dust begin to collect due to
gravity.
Once enough material has formed
together, a protostar is created.
This is the beginnings of what will
become a star. A star is born when nuclear
fusion begins.
Lifetimes of Stars
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Like automobiles burning through their
gas, the length a star lives depends on its
mass.
Larger, more massive stars live shorter
while less massive stars live longer.
Deaths of Stars
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As the star runs out of fuel, its core
shrinks and gets hotter.
As it does so, it heats the gases
surrounding it which causes the outer
layers to expand.
The star will then become a black dwarf
or black hole dependent upon its starting
mass.
Less Massive Stars
Nebula
Protostar
Low-mass or medium-mass star
Red Giant
Planetary Nebula
White Dwarf
Black Dwarf
Medium Sized Stars
• Medium sized stars are the most common in
the universe. An example is our sun.
Medium size stars are 10 times more
massive than a red dwarf
Red Giant
• 10-100 times the size of our sun. It shines
red and it is about 3000oC.
Planetary Nebula
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After the red giant, the star will create a
planetary nebula, which is the glowing gas
of the outer layers as they expand away
from the core.
White Dwarf
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The only thing that remains after is the
core of the star, a very hot dense, white
dwarf. After billions of years this will
eventually cool to become a black dwarf.
Greater Mass Stars
• Nebula
Protostar
High-mass star
Supernova
Supergiant
Neutron Star
Black Hole
Red Supergiant
• High mass stars quickly evolve into brilliant
supergiants.
Supernova
• All massive stars will explode in a
supernova.
Supernova Images
Neutron Stars
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The lower mass high mass stars will
instead become neutron stars.
Neutron stars spin rapidly and emit radio
waves.
Black Holes
• However, only the most massive will become
black holes.
• Remains of a supernova which contains enough
gravity that light cannot escape
• After a very massive star dies in a supernova
explosion, more than 5 times the mass of the sun
may be left
• The gravity of this mass is so strong that the gas is
pulled inward, packing the gas into smaller and
smaller space.
Black Holes
• Not able to detect a black hole directly because no
light, no radio waves, or any other form of
radiation can ever get out of a black hole
• Detect black hole indirectly
• Gas near a black hole is pulled so strongly that it
revolves faster and faster around the black hole
• Friction heats the gas up
• Astronomers can detect X-rays coming from the
hot gas and infer that a black hole is present
Reminders
• Only stars with more than 40 times the mass
of the sun form black holes when they die
• Other high mass stars become neutron stars
when they die
• When a star begins to run out of hydrogen,
it can become a red giant or supergiant
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