Black Hole Facts
Wondering what a black hole is? Well, it is basically the cold remnants of former stars – which are so dense that no matter (not even light) can escape the powerful gravitational pull. Most stars usually end up as white dwarfs or even neutron stars – but black holes are basically the last evolutionary stage in the lifetime of large stars that were at least 10 or 15 times as massive as the Sun itself. When these stars reach the final stages of their lives, they often blow up in cataclysms which are called supernovae. These explosions scatter most parts of the star into space, but sometimes a cold remnant is left behind – and on this no more fusion takes place.
Nuclear fusion creates energy in younger stars, there is a constant outward pressure which balances itself out with the inward pull of gravity which the star’s own mass causes. But when it comes to the dead remnants of the massive supernova, gravity is not opposed by any force – so the star begins to collapse in upon itself.
And since there is no force to check the pull of gravity, the budding black hole shrinks and shrinks till it reaches zero volume – and then it becomes infinitely dense. Even the light from this star cannot escape the strong gravitational pull. Thus the light becomes trapped in orbit, and this dark star, we call a black hole.
One interesting fact that you might not be aware of is that black holes pull matter and even energy into and within themselves – but not more so than other stars or even cosmic objects of similar mass. This basically means that a black hole with the mass of the sun, would not be able to suck objects into it any more than the sun does with its gravitational pull. Light, planets, and other kinds of matter must be relatively close to a black hole in order to be pulled or sucked into it. When they reach this point of no return, we say that they have reached the “Event Horizon” – from this point escape is absolutely impossible, because one would need to move faster than the speed of light.
Black holes are quite small – for instance, a million-solar-mass hole (which are believed to be at the center of some galaxies), might probably have a radius of about 2 million miles – which is about four times the size of the sun. So a black hole with a mass equal to that of the sun would have a two-mile radius. Black holes are small and distant, plus they’re also dark – this is why they cannot be observed directly. But of course they do exist – and this has been confirmed by scientists the world over. They do it by measuring mass in the sky’s region, and then looking out for areas of dark, large mass.
One can find black holes in binary star systems – these continually pull mass from the neighboring star – this makes the black hole bigger and bigger and thus the other star shrinks. Finally a point is reached when the black hole is really large and the neighboring star has vanished into nothingness. In the center of some galaxies, really large black holes can be found. Our own Milky Way is one such example. These black holes tend to have the size of at least 10 t0 100 billion suns. They grow to such big sizes because there is lots and lots of matter in the center of the galaxy for them to suck in. thus as they get so much matter into them, their mass increases, and they become even denser.
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According to Einstein’s theory of general relativity, a black hole is a place where the gravity is so high that time dilation occurs – time stops. This causes the Event Horizon – where objects fall in, or where matter is sucked in. those objects can never reappear.
Black holes have fascinated science-fiction lovers, they have captured the human imagination the world over – people nowadays talk about the concept of a “wormhole” – which is basically a theoretical tunnel which might allow rapid travel through time and space – but no evidence has been found to support the theory that this exists.