A black hole is a region in space where gravity is so strong that nothing-not even light-can escape its pull. This happens when a large amount of mass is concentrated into a very small area. Black holes form when massive stars run out of fuel and collapse under their own gravity in a powerful event called a supernova.

When a star explodes in a supernova, its outer layers are blasted into space, but the core may collapse inward. If the remaining mass is at least about three times that of the Sun, gravity compresses it into an incredibly dense point known as a singularity, surrounded by an invisible boundary called the event horizon. This boundary marks the point of no return-anything that crosses it is lost forever.

There are three main types of black holes:

• Stellar black holes, formed from dying stars.

• Supermassive black holes, found at the centers of galaxies and containing millions or billions of solar masses.

• Intermediate black holes, a possible middle class still under study.

Despite their name, black holes are not “holes” in the traditional sense-they are extremely dense objects. Their gravity is so intense because the mass is packed into a tiny volume. Time and space behave differently near them, creating fascinating effects predicted by Einstein’s theory of general relativity.

Though we cannot see black holes directly, scientists detect them through the effects they have on nearby matter, such as stars orbiting an invisible mass or X-rays emitted by gas falling into them.

A black hole forms from the gravitational collapse of a massive star. These mysterious objects are key to understanding gravity, space, and time in our universe.