How did the stars became a black hole?

Answer 1

Although it's not entirely known at the time, this is what is suspected:

When a super-massive star implodes to create a supernova, the power of the stars gravity becomes so strong that it warps the very fabric of space and time to create a "hole" that not even light can escape, ie a "Black Hole".

Please pay attention to the fact that only very large stars (at least 10 times the size of our sun), so the chances of a black hole forming is relatively low.

Answer 2

a sun is a mass of helium and hydrogen. when a sun gets too old, the gravity of itself gradually pulls the star into itself, making it infinitely small. the gravity gets stronger, pulling in every thing, even light, and sucking it into nothingness.

Answer 3

Not all stars become black holes. Some become white dwarf stars, and some become neutron stars. The answer to 'why' is rooted in Einstein's field equations, but we'll try to avoid the math and quantum physics. :)

Remember that any object with mass has a gravitational field that acts upon any other object with mass. The amount of mass of each object, and the distance between them, determines the gravitational pull that each object experiences. The closer the objects are together, the stronger the pull is. This is why astronauts float in space while we stand firm on the ground.

Gravity acts on every object with mass, including individual atoms. Every single atom on Earth pulls on every other atom. The reason that our planet is the nice oblate spheroid we've come to know, and love, is that all of those atoms pull on each other, but aren't strong enough to overcome the natural repulsive forces. Think of it like a big spring. The harder you push on one end of the spring, the closer you get to the other. If you can only press hard enough to compress the spring half way, that's as far as you get.

Black holes happen when the collection of objects with mass, in a given space, proves to be large enough that the combined gravitational field overcomes the natural repulsive forces.

Now let me take a short detour into the life of a star. Stars are big masses of gas that started burning because the combined mass of the gas was sufficient to pull the atoms very close together. Remember the spring analogy? You might not notice, but when you compress a spring it generates a bit of heat. Similarly, compress lots and lots of matter and you can generate enough heat to cause two atoms to fuse together. This fusion process emits energy in every direction, pushing other atoms away. Thus, a star is really a big mass of gas that is constantly trying to collapse, and constantly trying to explode from the released energy of the fusing atoms.

It takes a lot of energy to force two atoms to fuse together, and the amount of energy is proportional to the size of the atoms. Hydrogen takes less energy than Iron, for example. Thus, most of the fusion in a young star involves Hydrogen fusion. Over time, the star slowly runs low on hydrogen, and the fusion process starts using heavier and heavier elements. Eventually, the star reaches a point where something has to give. The outer layers of the star get blown away, leaving a hot, dense inner core. The initial size of the star determines just what happens from here.

The dense inner core is no longer able to sustain fusion and it slowly ceases. The matter that was always trying to collapse down is now unopposed. In smaller stars (like ours), the end result is a white dwarf. A bit bigger and you end up with a neutron star. Start big enough, and you get a black hole.

Lets return to the spring analogy. If you can push hard enough, the spring compresses down until all of the metal touches. At this point, it looks like a bumpy cylinder. If you could push even harder, you could compress it down into a ball of metal. What if you cold push harder still? Nobody knows. That's kind of like what happens with stars. We know that black holes can happen, but we don't really know what happens at the core of one. There are a lot of very interesting theories, though!