SPACE, EXPLAINED SIMPLY
Where gravity is so strong that even light cannot escape.
01
A black hole is a region where gravity is so strong that nothing, including light, can escape once it is inside the event horizon. It is not an empty hole: its defining feature is mass compressed into an extraordinarily compact region.
Some black holes form when massive stars collapse at the end of their lives. Supermassive black holes are found at the centres of large galaxies, including Sagittarius A* at the centre of the Milky Way.
02
Astronomers detect a black hole through its effect on nearby matter: the motion of stars, radiation from heated gas, and the bending of light. Merging black holes can also produce gravitational waves, measured by specialised observatories.
The bright ring in a black-hole image comes from matter and light near the black hole. It is not light escaping from within the event horizon.
03
No black hole acts like a cosmic vacuum cleaner at a distance. Far away, its gravity works just like the gravity of any other object with the same mass, so an object can orbit it safely.
If the Sun were replaced by a black hole of equal mass, Earth would not be swallowed immediately, although it would lose sunlight and heat. In reality, the Sun is not massive enough to end its life as a black hole.