First off what are black holes?
A black hole is a place in space where gravity is so enormous
that even light cannot escape. The gravity is so strong because
matter has been squeezed into a tiny space. This phenomenon can
happen when a star is dying.
So yes, a black hole is very dark, as is the space around it. In
turn, you cannot see black holes in space. In other words, a
black hole is invisible because huge gravity pulls all of the
light into the middle of it. However, when the black hole
consumes a star or nears one, the pairing produces high-energy
light which cannot be seen by the human eye, but becomes visible
when using satellite and telescopes with special tools. This
radiation is known as Hawking radiation, and was discovered by
one of the greatest theoretical physicists, Steven Hawking. He
published that the black hole should glow slightly with “Hawking
radiation” that is released and was discovered due to quantum
effects of the black holes. This high-energy light becomes
visible via the Hawking radiation.
The following link shows an animation from when NASA’s Swift
satellite spotted the black hole devouring a star in March 2011.
