Physics 17.1/2/3 The Life Cycle of Stars Flashcards
how do stars initially form
from nebula
what is a nebula
a cloud of dust and gas
how does the dust and gas turn into a star
gravity makes the dust and gas spiral in together to form a protostar
what happens to a protostar
it becomes denser due to gravity and temperature rises as particles inside the star speed up and collide more frequently.
what happens when the star reaches a certain temperature.
hydrogen nuclei undergo nuclear fusion to make helium nuclei. this creates huge amounts of energy, keeping the core hot.
what is a main sequence star
when a star reaches a long stable period where the outward pressure from nuclear fusion counteracts gravity.
how long does a main sequence star last
several billion years
what stage of its life cycle is our sun
main sequence
what happens after a main sequence
the hydrogen begins to run out and helium begins to fuse, forming other elements
where are elements created
elements heavier than helium (up to iron) are created in the core of a star and the rest are made in a supernova.
what happens to stars about the size of our sun when they die
It expands into a red giant (it runs out of hydrogen and cools down). It will then become unstable and eject its outer layer of dust and gas as planetary nebula, leaving a hot dense, solid core (a white dwarf). As the white dwarf cools, oit emits less and less energy, eventually becoming a black dwarf and disappearing from sight.
what happens when stars larger than our sun die
they expand into red supergiants. they expand and contract several times. This is where iron is created. eventually they run out of elements to fuse and become unstable. They explode in a supernova, throwing out the heavier elements to form new planets and stars. The stuff left behind is a very dense core called a neutron star. if it is big enough it become a black hole instead.
what is red shift
when the wavelength emitted from distant galaxies are longer and shift towards the red end of the spectrum
what does the fact that distant galaxies display red shift mean
that they are moving away from us therefore the universe is expanding. This also means that at some point they were closer to us so our universe expanded from one small point, supporting the big bang theory.
what is the big bang theory
the idea that the universe started as one tiny spot and suddenly exploded and has been expanding ever since. It exploded as all the matter was in a very small space and so was very dense and hot.
