Black holes facts

• The massive black hole at the center of the Milky Way galaxy is more than 4 million solar masses.
• It is now widely accepted that the center of every or at least nearly every galaxy contains a supermassive black hole.
• A black hole is the result of the deformation of spacetime caused by a very compact mass.
• It is called "black" because it absorbs all the light that hits it, reflecting nothing, just like a perfect black body in thermodynamics.
• The known closest black hole to Earth is Cygnus X-1, located about 8000 light years away.
• Some of the most notable galaxies with supermassive black hole candidates include M87, the Andromeda Galaxy, M32, NGC 3115, NGC 3377, NGC 4258, and the Sombrero Galaxy.
• The idea of a body so massive that even light could not escape was first put forward by geologist John Michell in a letter written to Henry Cavendish in 1783 to the Royal Society.
• "Dark stars" (black holes) were largely ignored in the 19th century, since it was not understood how a massless wave such as light could be influenced by gravity.
• Currently, the best evidence for a supermassive black hole comes from studying the proper motion of stars near the center of our own Milky Way galaxy.
• Although white holes are mathematically possible, there have yet to be observations to prove their existence.
• Despite its invisible interior, a black hole can be observed through its interaction with other matter.
• Black holes can suck up other black holes when they come in close proximity.
• The center of a black hole, the singularity, is the point where the laws of physics break down.