Black holes are sharks of the universe. People suffer from unjustified fear of them, although you really need to try to get close to at least one of them. Space is vast, and black holes, distant from our planet for thousands of light years, are nothing more than small islands in the vast ocean of the universe. And so those who want to look at them will need a large telescope.
Sagittarius a
When it comes to black holes in the Milky Way galaxy, the first that any astronomer would mention would be Sagittarius A (Sagittarius A). It lies at the very core of the Milky Way. Sagittarius A weighs 4 million times more than our Sun, but it’s only 6,000 times that. But this is not the closest black hole to Earth. It is 26 thousand light-years from our planet, therefore, in fact, it cannot be called our neighbor.
It is mentioned more often than others due to the fact that Sagittarius A is the nearest black hole to the Earth among supermassive stars, and besides, it is one of a kind within the Milky Way galaxy. Among all the other black holes in our galaxy, there is not one that would be heavier than the Sun more than 15 times.
V616 Monocerotis
The closest black hole to Earth is V616 Monocerotis. It is located at a distance of 3 thousand light years from Earth, its mass is approximately 9-13 times greater than the mass of the Sun. The second closest to us is the Cygnus X-1. It is located 6 thousand light years from Earth, its mass is 15 times the mass of the Sun. In third place is GRO J0422 +32. He separates us from her 7800 light years, and besides, she is the smallest black hole of all discovered at the moment.
These three space monsters have something else in common besides the fact that these are the three closest black holes to Earth. All three have satellites. It was thanks to the satellites that they were discovered. The black hole, attracting the planet harder and harder, gradually begins to absorb it, but before the victim plunges beyond the horizon of events, it heats up and begins to emit x-rays. X-ray tracking is the most effective way to search for black holes. Telescopes like NASA Chandra are the best black hole hunters. It was Chandra who first found the V616 Monocerotis - the closest black hole to Earth.
Difficulty finding
Black holes, as their name implies, are completely black. The gravitational field of a black hole is so powerful that it attracts and draws even light into itself. Given the general blackness of the cosmos, this factor becomes a significant obstacle in the search for sharks in the universe.
They distort space and time, therefore, ideally, one could search for them by the microlensing effect - subtle deviations in the light of distant stars. But the chances of success are practically nil. This method will work only if the distant star and the black hole line up.
How many black holes exist?
Currently, we can estimate the number of black holes based on the number of supernovae. According to researchers, over the past millions of years, about 20 thousand star explosions have occurred on the Milky Way. If no tangible changes have occurred in the number of stellar explosions over the past 12 billion years, tens of millions of black holes should be hidden in the Milky Way.
The Milky Way takes 100 thousand light-years long and 1 thousand light-years wide. This is approximately 7.86 trillion cubic light years. If we assume that there are only 1 million black holes in our galaxy, this means that for every 125 light-years there is one shark in the universe. Obviously, this is a very crude assumption. In addition, black holes are not so evenly distributed in space.
Nevertheless, there are a huge number of still not discovered black stars. They will not be found in one night, but nevertheless, new surprising observations will undoubtedly give us the opportunity to find out many interesting facts related to black holes. It is possible that in the near future V616 Monocerotis will cede its title of the closest black hole to Earth to some other terrible giant.