Download Star Life Cycles

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What percentage of stars you can see in the nighttime sky are located in our solar system?
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What percentage of stars you can see in the nighttime sky are located in our galaxy?
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All stars follow a very specific life cycle.
All stars begin in the same way.
The size of the star determines how the star will “die.”
All stars begin their lives in a stellar nebula as cool clouds of gas and dust.
Once the cloud of gas and dust begins collapsing in on itself, it becomes a protostar.
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The next stage of a star’s life is called Main
Sequence
Main sequence stars are stars, like our Sun, that fuse
hydrogen atoms together to make helium atoms in
their cores.
Since stars have a limited supply of hydrogen in their
cores, they have a limited lifetime as main sequence
stars.
The amount of mass and the luminosity, or brightness
of stars, determines the length of their lives.
It is at this point that stars will take different paths.
ƒ The amount of mass in stars determines what they will become after their death.
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Stars the size of our sun or smaller become red giants.
As hydrogen in the core is consumed, the core of the star loses gravity.
Eventually, the outer parts of the star expand away from the core and its decreased gravity.
Red giants eventually become planetary nebula where the outer layers of the star are blown away leaving only the hot, dense core
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After becoming a planetary nebula, the remains of the core of the star become a white dwarf.
A white dwarf is a star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size; such a star is near its final stage of life. White dwarfs eventually become black dwarfs, which is a white dwarf that has cooled down enough that it no longer emits light. Interesting Fact: The universe is not old enough to have any black dwarf stars yet.
Stars that are more massive than our Sun can become Red Supergiants.
ƒ Red Supergiants can be 100 times larger than the sun.
ƒ Betelgeuse, located in the constellation Orion, is the most well‐known example of a Red SuperGiant.
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Eventually Red Super Giants will explode in something called a Supernova.
A supernova occurs when a star with
many times the mass of the Sun runs out
of usable nuclear fuel.
The Crab Nebula is an example of the
remnants of supernova.
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Neutron stars are the collapsed cores of some massive stars. They pack roughly the mass of our Sun into a region the size of a city.
Black Holes form from the most massive of stars.
Black holes have such strong gravity that nothing, not even light, can escape their grip.
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protostar
Note: This graphic does not show protostars or black dwarves.
Where would they go in this diagram?
Read pages 40‐45
Draw a star life cycle flow chart in your notebook. (similar to previous slide) Include all stages discussed in class.
ƒ Pay particular attention to the H‐R diagram information on pages42‐43. You MUST understand the information this diagram presents.
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