What happens to a star when it and life ends?

Answer 1

What happens at the "end" of a star's life depends almost entirely on the original mass of the star. It will become a white dwarf star, a neutron star or a black hole.

Small red dwarf stars will fade into white dwarf and (eventually) black dwarf stars. They fuse hydrogen into helium, but don't have enough mass to ever fuse helium into heavier elements, so as their fuel is exhausted, they will shine more and more dimly. Of course, red dwarf stars aren't very bright to begin with; the closest star to our Sun is the red dwarf Proxima Centauri, at 4.2 light years distance, and it is so dim that it cannot be seen without a telescope. Some Red dwarf stars could, for all practical purposes, last forever. Some will become become white dwarfs.

Stars like our Sun burn hydrogen, but in another 4 billion years or so, the hydrogen will be substantially depleted, and an "ash" of helium will impede the hydrogen fusion. The Sun will shine less brightly, and there won't be enough heat to keep the star from collapsing, so it will begin to collapse. This will increase the heat and pressure in the core, and at some point the Sun will begin to fuse helium into heavier elements, GREATLY increasing its energy supply. The Sun will expand into a red giant, which will certainly consume the planets Mercury and Venus, and probably the Earth itself (if we haven't moved it elsewhere for safely). But the Sun doesn't have enough mass to go "supernova" and explode, so it will settle into a long decline into, probably, a whitedwarf star.

Stars of mass greater than about 8 times the Sun's mass will eventually go supernova and explode, throwing some of their mass back into space and contributing to the next generation of stars and planets. (Our solar system is probably third generation; some of our mass has already been through a supernova.) The end result of a supernova would probably be a neutronstar or a blackhole.

It's also important to know that the more massive the star, the faster it burns and the more quickly it will die. Our Sun will likely be about 10 billion years old when it expands into a red giant. A red dwarf would probably last 100 billion years or more. And a massive star will explode quickly. For example, the giant star Betelgeuse, at the shoulder of the constellation Orion, is only a few hundred million years old - and will probably go supernova within the next 50,000 years.