1When a truly massive star finally exhausts its nuclear fuel, its life ends in a violent way.
2Without the outward pressure of burning fuel, the core collapses inward under its own tremendous gravity.
3At the same time, the outer layers of the star are blasted into space in a supernova explosion.
4For a few short weeks, the brilliant light of one dying star can outshine an entire galaxy.
5What remains of the collapsed core may then continue to shrink and finally become a black hole.
6A black hole is a region of space where gravity is so incredibly strong that nothing escapes.
7Not even light, which is the fastest thing in the entire universe, can ever get away from it.
8Because astronomers cannot observe black holes directly, they must carefully study their powerful effects on nearby matter.
9Nearby stars wobble strangely, and gas spirals inward, glowing fiercely as it falls toward the hole.
10In recent years, a network of telescopes has even captured the dark shadow of a black hole.
11These remarkable observations confirm the bold predictions that Albert Einstein first made more than a century ago.
12Yet the hidden interior of a black hole still remains one of the deepest mysteries in science.