A black hole is a place in space that is extremely dense and has a strong gravitational pull. This is because a lot of matter has been squeezed into a tiny space. This usually happens when a star is dying. Black holes can suck in entire stars and planets! Black holes can be from the size of a single atom to the size of the Sun! Black holes are still mysterious because even light can’t escape a black hole, meaning that scientists can’t see them. But, they can see the movement of stars around the black hole and study it this way.