Life cycle of stars
Stars the same size or smaller than the sun:
Nebula (cloud of dust and gas) gravity pulls dust and gas together
Protostar gets larger and larger as gravity attracts more dust and gas, gravity squeezes the protostar so it gets more dense and particles collide more often (temp also increases) leading to the beginning of nuclear fusion between hydrogen nuclei
Main sequence star Outward pressure from fusion energy is balanced by the gravity pressure leading to a long stable period until the star runs out of hydrogen. Fusion stops and inwards pressure of gravity takes over until the star contracts into a small, dense ball. WHen the ball is dense and hot enough, nuclear fusion starts again to create heavier elements (up to Iron-56), allowing the star to expand again
Red giant becomes unstable and expels outer layers to leave a hot, dense solid core called a white dwarf
White dwarf gets cooler and darker as it emits its energy until it becomes a black dwarf
Stars much larger than the sun:
Nebula (cloud of dust and gas) gravity pulls dust and gas together
Protostar gets larger and larger as gravity attracts more dust and gas, gravity squeezes the protostar so it gets more dense and particles collide more often (temp also increases) leading to the beginning of nuclear fusion between hydrogen nuclei
Main sequence star Outward pressure from fusion energy is balanced by the gravity pressure leading to a long stable period until the star runs out of hydrogen. Fusion stops and inwards pressure of gravity takes over until the star contracts into a small, dense ball. WHen the ball is dense and hot enough, nuclear fusion starts again to create heavier elements (up to Iron-56), allowing the star to expand again
Red super giant Undergoes more fusion of elements greater than iron-56
It explodes into a supernova where elements heavier than iron are ejected across the universe to form new planets and stars
If very big: condenses into a neutron star
If massive: collapses in on itself and becomes a black hole