What percentage of stars will become black holes?
Roughly one out of every thousand stars that form is massive enough to become a black hole. Therefore, our galaxy must harbor some 100 million stellar-mass black holes. Most of these are invisible to us, and only about a dozen have been identified.
Some smaller stars are big enough to go supernova, but too small to become black holes — they'll collapse into super-dense structures called neutron stars after exploding as a supernova.
— When the most massive stars die, they collapse under their own gravity and leave behind black holes; when stars that are a bit less massive than this die, they explode and leave behind dense, dead remnants of stars called neutron stars.
When stars die, they become either black holes, neutron stars, or white dwarfs.
This process could take a million years or more depending on how quickly it accretes the material, but once the neutron star is over the limit, which is about 3 solar masses, the collapse to a black hole occurs in less than a second.
The large stars are most likely to form the black holes. This is because the black holes form from the remnants of a larger star that dies in the explosion of the supernova. Neutron stars can form a black hole.
So-called direct-collapse black holes wouldn't need to wait for a star to die to form them. Instead, clusters of early galaxies could influence each other. If you have two or more early galaxies near each other, one may undergo rapid star formation.
Above that mass, stars are so massive that they likely collapse into a black hole directly, without becoming a supernova. Extremely massive stars, on the order of 150 solar masses or more, might explode as a hypernova.
No. Stars like the Sun just aren't massive enough to become black holes. Instead, in several billion years, the Sun will cast off its outer layers, and its core will form a white dwarf - a dense ball of carbon and oxygen that no longer produces nuclear energy, but that shines because it is very hot.
In general, stars with final masses in the range 2 to 3 solar masses are believed to ultimately collapse to a black hole.
What's worse than a black hole?
There are no classes of object in our Universe more extreme than black holes. With so much mass present in such a tiny volume of space, they create a region around them where the curvature of space is so strong that nothing — not even light — can escape from its gravity once a certain boundary is crossed.
The short answer, unfortunately, is no. White holes are really just something scientists have imagined — they could exist, but we've never seen one, or even seen clues that one may exist. For now, they are an idea. To put it simply, you can imagine a white hole as being a black hole in reverse.
Even if we see the universe from a point very close to the apparent event horizon, the time dilates to such an extent that the time of the locations away from tne universe will be much faster (say 1 second for the observer near blak hole will be 100000 years for an observer on earth).
So planets could potentially form around black holes, but that's no guarantee that they offer a life-friendly environment. On Earth, living things are hugely dependent on the light and warmth from the Sun to survive. Without the glow of a star, life around a black hole would likely need an alternative source of energy.
In theory, any mass can be compressed sufficiently to form a black hole. The only requirement is that its physical size is less than the Schwarzschild radius. For example, our Sun would become a black hole if its mass was contained within a sphere about 2.5 km across.
Astronomers think nearly every galaxy hosts a giant black hole in its core. And while those black holes truly are massive — weighing millions, or even billions, of solar masses — they are tiny compared with their home galaxies, reaching less than 1% of the mass of a typical galaxy and a volume a billion times smaller.
there will be very strong pressure gradients which oppose the star gravitational collapse. For massive stars, radiation pressure much exceeds gas pressure, while the reverse occurs in low mass stars like the Sun, because of its low luminosity of course.
Two supermassive black holes have been spotted feasting on cosmic materials as two galaxies in distant space merge — and are the closest to colliding black holes astronomers have ever observed.
Astronomers estimate that 100 million black holes roam among the stars in our Milky Way galaxy, but they have never conclusively identified an isolated black hole.
A black hole at the heart of the dwarf galaxy Henize 2-10 is creating stars rather than gobbling them up. The black hole is apparently contributing to the firestorm of new star formation taking place in the galaxy. The dwarf galaxy lies 30 million light-years away, in the southern constellation Pyxis.
Do all stars eventually explode?
Luckily for us, not all stars explode and then die. When stars age, they change from a dwarf star (our Sun is actually currently a dwarf star) into a giant star. If a star is big enough it can then explode in what we call a “core-collapse supernova”.