What are black holes?

Credit: ESO/L. Calçada/M.Kornmesser

When a massive star dies, its core collapses into a superdense, rapidly spinning neutron star, or even into a black hole – a mysterious object from which not even light can escape.

Pinball black hole: The black hole remnant of a stellar explosion is no longer in the centre of the expanding supernova remnant, but is kicked into space, together with its companion star (artist impression).
Credit: ESA, NASA and Felix Mirabel (the French Atomic Energy Commission & the Institute for Astronomy and Space Physics/Conicet of Argentina)

What’s left after a massive star goes supernova depends on the mass of its core. If it’s between 1.4 and about 3 solar masses, the strength of nuclear particles balances the force of gravity. The resulting neutron star is less than 30 kilometres across and has the highest density known in the Universe. If the core is more massive, even neutrons are crushed out of existence. The result is a black hole – a mysterious object with a gravitational field strong enough to trap even light.

Don’t get too close to a black hole! If you fall in you can’t get out again, even with the fastest rocket. Not even light can escape! That’s why it’s pitch black.