The life cycle of a star

what is nuclear fusion

when two smaller nuclei fuse together to create a larger nucleus, releasing a large amount of energy

why can nuclear fusion occur on the sun but not earth

because there isnt access to enough energy on earth to overcome the repulsion of two nuclei to fuse

what are stars made of

hydrogen

where does all the matter stars have come from

the big bang

what does nuclear fusion of two hydrogen nuclei make?

a helium nucleus

what is the first stage of a star’s life and what is it?

nebula, a cloud of dust and particles in space that came from the start of the universe and other dead stars

what is the second stage of a star’s life

protostar, the gravitational energy of the particles cause them to gather together and the kinetic energy causes nuclear fusion of hydrogen

what is the main part of a star’s life called

main phase

how long do stars stay in its main phase?

billions of years

what causes a star to start dying

when it starts to run out of hydrogen to keep

what keeps a star stable and equilibrium?

the amount of energy going in, keeping the star together (due to gravity) is equal to the amount of energy being released (due to nuclear fusion)

why were earlier stars thought to have been bigger than the Sun?

there was a lot of matter that hadn’t been distributed and no planets had formed yet because there were no heavier metals

how are planets made?

gravitational energy brings particles together but there is not enough energy to start new fusion reactions