Humanity’s discovery of black holes started in the early 1900s, back when Swarzschild and Einstein were making insane scientific waves. However, they didn’t believe in the possibility, even though the theory of the event horizon was established.
Back in 1964, when evidence of the first black hole was discovered. The Cygnus X-1 was identified by scientists using X-Ray technology. And they’ve learned more about these celestial bodies since then.
The Sagittarius A* is at the heart of the Milky Way, estimated to be at least four times larger than the sun. According to NASA, it’s 26,000 light-years from the earth.
A black hole cannot be seen because it traps everything that falls within its horizon. It has the strongest gravitational fields; even light cannot escape the pull.