Black Hole

 Document and record (Wikipedia) :

A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.

​ Researchers observation :

1. ​Our Milky Way Probably Has a Black Hole.
2. ​The Closest Black Hole is Probably Not 1,600 Light-Years Away.
3. ​You Can't Directly See a Black Hole. 

Literature sources

NOBODY has ever seen a black hole. Yet, despite this lack of direct evidence, most scientists believe that a massive star at the end of its life can implode to form an object so dense that nothing-not even light-can escape. ... In fact, they seemto fit all the observational evidence for the existence of black holes.