Describe the life and death of stars?
It’s a large question… stars form when clouds of hydrogen (and other light elements) are pulled together because of gravity. As more & more material clump together, it creates pressure and heat at the core. When *enough* material is present to create the heat & pressure needed, the star begins fusing the hydrogen into helium.
A core of helium material begins to build in the center of star. If the star is massive (more than 3 to 8 times as much as our sun), then inside this helium core, a *second* fusion process starts – fusing helium into lithium. If the star is massive enough, then again – another fusion process starts.
Small stars, our sun included, aren’t heavy enough to have multiple cores, and it’ll burn steady for billions of years longer than the most massive stars, that burn their fuel much quicker.
The death of stars… if a star is fairly small, when it’s out of hydrogen, it’ll begin to swell, sloughing off it’s outer layers in a few hundred thousand years… our sun will swell until Earth is essentially swallowed. When the material has been blown off, what’s left is the super-hot core, which no longer fuses material, and it’ll cool from a white dwarf to a black dwarf over millions of years.
Larger stars will have a much stronger reaction – a supernova. When a large star runs out of material to fuse, the reaction that has kept the star ‘inflated’ to it’s size stops – and there’s no outward force to counter the immense gravity. The star collapses onto it’s core – and a huge explosion occurs. The explosion happens just outside the inner core – blowing off huge amounts of material, and compressing the core.
Depending on the mass of the core and the force of the supernova, the core can be compressed so much that the electrons and protons of all it’s atoms are crushed together to form a mass of nothing but neutrons – a neutron star. It’s usually about 8 to 20 miles in diameter, and super dense.
If there’s ENOUGH mass, then compression doesn’t stop at the neutron star stage – it keeps collapsing until space can no longer support it – it becomes a black hole. A black hole is essentially a dimensionless point in space; the only indication to how massive it is will be the size of it’s Event Horizon. They’re usually 6-12 miles across for newly formed black holes, but they grow as more & more material falls in.