In astronomy, what are so dense that not even light can escape their gravity?
red holes
black rods
dwarf stars
black holes
If the core remaining after a supernova is more than about 5 times the mass of the Sun, the core collapses to become a black hole . Black holes are so dense that not even light can escape their gravity. For that reason, we can't see black holes. How can we know something exists if radiation can't escape it? We know a black hole is there by the effect that it has on objects around it. Also, some radiation leaks out around its edges. A black hole isn't a hole at all. It is the tremendously dense core of a supermassive star.