A black hole is a region of spacetime where gravity is so strong that nothing, including light and other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon, which is the defining feature of a black hole. Nothing, not even light, can escape from inside the event horizon. Although it has a great effect on the fate and circumstances of an object crossing it, it has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body, as it reflects no light.

There are four types of black holes: stellar, intermediate, supermassive, and miniature. Most black holes form from the remnants of a large star that dies in a supernova explosion, and the resulting gravitational field is incredibly powerful. Smaller stars become dense neutron stars, which are not massive enough to form a black hole. Stellar black holes are made when the center of a very big star falls in upon itself, or collapses, causing a supernova. Supermassive black holes were made at the same time as the galaxy. The largest black holes are called “supermassive,” and they have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center.

Black holes cannot be directly observed with telescopes that detect x-rays, light, or other forms of electromagnetic radiation. However, scientists can infer their presence and study them by detecting their effect on nearby matter. For example, if a black hole passes through a cloud of interstellar matter, it can cause the matter to be drawn towards it due to its strong gravitational pull. In 2019, the Event Horizon Telescope (EHT) collaboration released the first image ever recorded of a black hole. The EHT saw the black hole in the center of galaxy M87 while the telescope was examining the event horizon or the area past which nothing can escape from a black hole[[4]](https://www.space.com/15...