What happens when the sun explodes and forms a black hole?
Our sun won't do that, don't worry.
All the stars light up using the same principle, that is fusion of hydrogen to helium and thus releasing energy.
What happens when the hydrogen supply runs off?? It again starts to fuse helium to form heavier elements, and thus this chain goes on till we reach to iron, because when iron fuses, it doesn't release energy rather consume it, this is the beginning of death of a star.
Not every star face the same fate, small star such as our sun, when run off of fuel, expands and becomes a red giant, with outer layer red and thus of lower temperature (because of iron generation). And when outer layer cools off and disappears, we are left with a white dwarf, a dense cold remain of a star. Our sun will face the same fate.(after around 4 billion years)
While bigger stars,(about 1.4 times mass of our sun, Chandrashekhar limit 1985 Nobel prize) runs low on fuel, they also expand, but as their gravitational pull is so strong, at one point its core collapse and suddenly burst releasing brilliant light that is visible in whole Galaxy. It is called supernova.( It is from a supernova that heavier elements are made, such as gold, silver, uranium, your gold ring was made in the heart of a dying star, not only this)
Our sun is not that massive to become a black hole it can become a neutron star with a supernova explosion.
If the sun were replaced by a neutron star with the same mass as the sun, every thing will remain the same as it is now, except for the fact that all the planets will freeze and we all die, not due to gravity or something, but due to cold and lack of sun's rays and photosynthesis, but mainly due to cold.
Planets will continue to orbit around as they are doing right now, but it would be all night no day, and it will be cold, and winter will come and it won't go.
But as a star will lose most of its mass in supernova explosion, then there will be a change in gravitational pull also.
So things don't look good as far as survival is concerned.
To have a quick understanding about neutron stars watch our video.
That will never be. A star needs to be more than fifteen to twenty five times heavier than the Sun to make a black hole. And more than eight times to explode.
The Sun will just puff up, go red, then fade away uneventfully.
I think previous answers on LinkedIn say our sun is not big enough to form a black hole when it goes supernova. It is predicted to to expand burning the Earth. We would be advised not to be around when that happens. In some other models our sun already has a black hole at it's core. I am not sure this idea is very well established. In any case if there was a black hole in the sun it has not consumed the rest of the sun yet. If it did it would have the same mass as it does now and Earth's orbit should be the same. What would be different is we would have no light or heat from our sun. This would be bad for us.