Stars
Stars form when dust and gas are pulled by gravity and clump together.
As they clump together, they get hot, they form a start when they are hot enough for nuclear fusion to start which releases energy and keep the star hot.
A star is stable because the forces are balanced. Outward pressure from expanding gasses are balanced by the force of the star's gravity.
When hydrogen has been used up it starts to fuse larger nuclei and it expands to become a red giant
When the nuclear reactions are over as the star can no longer fuse larger nuclei, they may begin to contract from the pull of gravity. It forms a white dwarf which fades and cools.
For a start with more mass, they will keep making nuclear reactions, expands and get hotter until it explodes as a supernova and throws dust + gases away. It collapses into a black hole or a neutron star.
Planets are formed when gravity pulls smaller amount of dust and gas together
Life cycles of star
Protostar > Main sequence star (Our sun)
Red giant > White dwarf > Black Dwarf (Path of Our sun)
Red super giant star> Supernova > Neutron star / Black hole.
Temperatures and pressures inside a star is great enough for nuclear fusion to happen.
Stars have enough hydrogen to maintain their energy output for million of years.
Hydrogen nuclei fuse together to form helium nuclei.
In a red giant star, the start fuse heavier elements from helium to iron.
Elements heavier than iron are formed in supernovas.
Heavy elements are found in suns and stars which suggest the solar system are formed from remains of supernovas
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