Do Black Holes really exist?
Everybody knows nothing can escape a black hole, not even light, so how can we see them? How can we say that they really exist?
Though they can be completely invisible to electromagnetic radiation, black holes have many interactions with the matter around them. So when we see one of these interactions happening we can conclude that the most likely explanation is indeed a black hole.
But let’s see what are the main phenomena caused by black holes that scientists have discovered:
A blaze of X-rays
Matter around the black hole is drawn spirally toward the hole. While it’s on the edge of the hole it heats up and reaches millions of degrees. This forms a disk of matter glowing in X-rays, which can be seen by X-ray telescopes such as Chandra, and it’s a characteristic fingerprint of a black hole.
Super-powerful jets of matter
Jets of matter are observed to be shoot out from the center of a galaxy. This jets are enormously powerful and the only known source able to produce them is a giant spinning black hole. Although how a black hole can create these jets is still unknown, they seem to originate from the outside of their event horizon.
Rapidly moving stars
The enormous gravitational field of super-massive black holes will make stars orbiting them at an incredible speed. At first glance these stars would seem to orbit “nothing”, but following their motion astronomers can deduce the location and the size of the central black hole.
Black holes was initially theoretically hypothesized in 1939 by Oppenheimer and Snyder using equations of Einstein’s general relativity. Although Einstein himself didn’t believe that a black hole could ever form, what we have seen are the main evidence known today of the their existence.