A black hole is a region of spacetime where gravity is so strong that nothing, not even light, can escape from it. Black holes are formed when massive stars collapse at the end of their life cycle.
Examples
**Example:** The supermassive black hole at the center of our Milky Way, called Sagittarius A*, has a mass of about 4 million times that of our Sun. The first black hole ever photographed, M87*, has a mass of 6.5 billion solar masses.