How do black holes form?

Black holes form when a massive star reaches the end of its life and exhausts its nuclear fuel. Here is the general process:

1. Collapse: Throughout its life, a star maintains a balance between the inward pull of gravity and the outward pressure from nuclear fusion in its core. When the star runs out of fuel, that outward pressure stops. Gravity takes over, and the core collapses inward.
2. Supernova: If the star is massive enough (generally at least 10–20 times the mass of our Sun), the outer layers of the star are blown away in a massive explosion called a supernova.
3. Formation: After the explosion, the remaining core is crushed under its own weight. If the remaining core mass is sufficiently high, nothing can stop the collapse. It continues until all the matter is squeezed into a point of infinite density called a singularity, surrounded by a boundary known as the event horizon, from which nothing—not even light—can escape.

Not all stars become black holes. Lower-mass stars, like our Sun, eventually collapse into much smaller, dense objects called white dwarfs and do not have enough mass to form a black hole.