If our sun dies, will it become another black hole
Our Sun is too small to be a black hole.
As it exhausts its hydrogen fuel, our Sun will begin to burn helium, swell in size and briefly become a red giant (massive in size, though not in mass), possibly the size of the orbit of Venus or will be more.
However, once the helium fuel is exhausted, the Sun will shrink into a white dwarf, which is still luminous because of the tremendous amount of heat trapped inside, but no longer burning any fuel.
Thus begins a long cooling process, which represents the final stage for a star like our Sun.
Large stars can have enough mass to create the pressure and temperature needed inside their cores to fuse heavier elements, e.g., oxygen and carbon.
But our Sun is too small for that, so no such fusion will happen.
The end of life for those very massive stars can be very violent: as they run out of fuel, they reach a threshold when their cores rapidly collapse, releasing enormous amounts of energy that are left behind by the rest blows up the stars.
This is a so-called core collapse supernova. Remnants can turn into a dwarf star; Or if it is heavy enough (currently at least 50% heavier than our Sun) it could further collapse into a neutron star.
Finally, if the remnant is at least three times as massive as our Sun, the collapse will not stop there either, but will continue, and become a black hole.
But not in our Sun. As I said, our Sun is too lightweight for these dramatic events.
In nut-shell
As stated earlier, hydrogen dissolves into helium which settles in the center of the core.
Now the helium is fusing into the carbon which is now again settling at the core and the carbon requires a temperature of 600 million degrees Kelvin to initiate fusion.
A star the same mass as the Sun would not have enough carbon at the core.
You need a lot of carbon atoms to compress enough to produce 600 million degrees Kelvin.
Smaller mass stars simply do not have enough mass and it all starts with the amount of hydrogen at the time of the stars’ birth.
Why do most massive stars end up as black holes instead of neutron stars. Massive stars have enough initial hydrogen and these giant stars will initially go through the same fusion cycle as the Sun, hydrogen to helium and helium to carbon, but now there is enough matter that the star can continue the fusion cycle from hydrogen- helium- carbon-neon-oxygen-magnesium-silicon and sulfur and finally iron.
All of the above fusion cycles generate energy (pressure) and will maintain some degree of hydra-static equilibrium, although at increasing degrees of instability,
but once the star runs out of silicon, the star cannot fuse to iron. Do this because the star needs energy and the star cannot borrow this energy from a friend.
In a split second the star becomes trapped under extreme gravity.
That would happen and about 15% of the speed of light. The energy generated by this explosion is of such intensity that the star had never experienced it before.
This energy explodes outward and collides with the explosion of incoming matter at 15% of the speed of light resulting in a supernova.
The remnants of this supernova will either end up as a neutron star or a black hole.
Things that will change
Of course, without light from the Sun, life on Earth would be in serious trouble.
The Earth would start to cool and the carbon cycle would be disrupted without photosynthesis, which would break down CO to produce O2.
Plants will start dying due to lack of photosynthesis and animals will start dying due to the decreasing amount of plants and gradually decreasing O2 content of the atmosphere.
We will all eventually die from exposure to the cold as well.
Not sure about the timing of these various problems, so I can’t say what will hit us first, but the outcome is certain.
We will all die. Its passing would be comparatively peaceful (though it would still scorch, perhaps even be consumed when Earth dies).
