Black holes are objects which we would never want in our neighborhoods. Deadly for the much larger objects than our tiny planet, black holes are true monsters of the Universe. Although we distinguish black holes by its size such as small, supermassive and recently discovered an intermediate-mass black hole, all of them possess immense power.
Just think about it, we are dealing here with regions of space where matter is compressed so densely that the only way to escape is to be traveling faster than the speed of light. And we know that this is impossible, for now. But does we have reasons to be feared that one day we might encounter with them? According to current data, we are safe.
Black holes are hard to be detected. They are invisible and do not emit any radiation. Still, astronomers have to track them. So, how they spot them? Indirectly, through the distortion of background starlight. Thanks to it, we were able to detect our nearest holes. Besides the biggest black hole in Milky Way, Sagittarius A, which is located in the galactic center and 26,000 light-years from the Solar System, there are numerous holes in our galaxy. The nearest are:
This black hole, also known as V616 Mon is located in a binary system with a star with about half the mass of the Sun, named A0620-00. The distance is approximately 3,000 light years. Its mass is between 9-13 times the mass of the Sun. Although it is the closest known hole, it is not a threat.
One of the best known and nearest stellar black holes is the Cygnes X-1 lying in the constellation Cygnus. Discovered in 1964, it is about 8,000 light-years away. Cygnus X-1 belongs to a high-mass X-ray binary system. The tell-tale signs that a black hole is at work are the rapidly flickering X-rays that come from the super-hot material, stolen from the bright supergiant. There are some suggestions that this hole is about five million years old.
Another black hole detected in constellation Cygnus and it is also in a binary system. It is discovered in 1989, but on 15 June 2015 NASA’s Swift satellite detected the first signs of renewed activity. V404 Cygni distance is approximately 7,800 light years.
As we can see, there is a pattern of detection black holes. We only spotted them in binary systems, but that doesn’t mean they are not elsewhere too. We can only hope that future instruments will find the way for better detection and eventually warn us about unwanted neighbors.