What is a black hole? How can we understand it?

A black hole is a region of space where gravity is so strong that nothing not even light can escape. It forms when an extremely massive star collapses at the end of its life. The core compresses to an almost infinitely dense point called a singularity.

The boundary beyond which nothing can return is called the event horizon. It is not a physical surface it is a point of no return.

Simple analogy: imagine a rubber sheet pulled tight. Place a bowling ball on it the sheet sags. A black hole is an infinitely heavy point creating a bottomless funnel. Anything that rolls too close falls in and cannot climb back out.

Black holes cannot be seen directly they emit no light. We detect them by their effects: gas spiraling in heats up and glows brilliantly (an accretion disk), and nearby stars orbit them at measurable speeds. In 2019, the Event Horizon Telescope captured the first image of a black hole's shadow in galaxy M87.