LIFE CYCLE OF A STAR Flashcards
how do stars originally form?
stars initially fork from a cloud of dust and gas called a nebula
what is the second stage of the life cycle of a star and how is it formed?
protostar
gravity pulls the dust and gas together to form a protostar
the temperature rises as the star gets denser and more particles collide
as it gets hot enough hydrogen nuclei undergo nuclear fusion to form helium nuclei
this gives our huge amounts of energy which keeps the core of stars hot
what is the 3rd stage of the life cycle of a star and describe what happens at this stage:
main sequence star
the star enters a long stable period where the outward pressure causes by nuclear fusion balances the force of gravity trying to pull everything together
lasts around 7 billion years
what happens to a main sequence star about the size of our sun after it’s main sequence?
red giant
eventually the hydrogen begins to run out therefore the surface becomes red as it cools
fusion of helium and other elements occur
heavier elements up to iron are created in the core of the star
what happens to the star after it becomes a red giant?
becomes a white dwarf
it becomes unstable and ejects the outer layer of dust and gas
leaving behind a dense solid core called a white dwarf
what happens to a white dwarf as it cools down?
it emits less and less energy
when it no longer emits a significant amount it is called a black dwarf
what happens to a main sequence star much bigger than our sun after it’s main sequence?
the star swells into a red super giant
because the surface cools down
fusion of helium and other elements occur
heavy elements up to iron are created here
what happens after a red super giant?
start to glow brightly again
as they undergo more fusion and expand and contract many times
they form heavy elements such as iron in various nuclear reactions which eventually makes them explode into a supernova.
the explosion called a supernova forms elements heavier than iron and eject them into the universe forming new planets and stars
what happens after a supernova explosion?
the exploding supernova throws the outer layers of gas and dust into space leaving a very dense core behind called a neutron star
if the star is massive enough it can form a black hole instead
what is a black hole?
a super dense point in space that not even light can escape
