If you’ve read or watched any science fiction the odds are good that at some point you have come across the concept of a black hole. These are scattered across science fiction stories and while sometimes there is a cursory explanation of what they are more often than not you only get hints. The reason that science fiction authors uses these odd occurrences in nature so often is that they are one of the most interesting ideas in modern astrophysics.
A black hole is, at its most basic, a star which is so massive that even light can not escape from it. The black hole is formed at the end of the stars life as it condenses in on itself. This is called Gravitational Collapse and creates a black hole. At the center of a black hole is a singularity where the laws of physics are so dominated by gravity as to be completely different.
Although the name of the black hole is new, the idea was first written of in 1783 in a letter written by John Michell, but there was no real evidence that this was possible until Einstein discovered general relatively and proved that gravity could influence light.
The difficulty of detecting black holes is self evident. The problem is that by definition a black hole does not emit light and since most of our knowledge of the stars are by looking at their light new ways have to be discovered to examine black holes.
Nearly all evidence of black holes is through indirect observation, and there are a few ways to do this. The first of these is by watching the matter that is being drawn into a black hole. They form distinctive disk like structures. The second is similar to the way that Pluto was discovered. A black hole has an effect on stars around it and by watching their movements it is possible to determine that there are black holes nearby and even where they are likely to be.
Although black holes were once assumed to be rare if they existed at all it has become more clear that they do exist and may be reasonably common in the universe. In fact there are some scientists who believe that there may be super massive black holes in the center of many if not most of the galaxies of our universe and can account for much of the dark matter in the universe.
