1 MSTARTED LIFE AS STARS ANY BLACK HOLES
Stars spend their entire lifetimes resisting gravitational collapse. Their enormous masses mean that their gas is continually pulled towards their cores, but instead of collapsing down, atoms collide and fuse, releasing explosive atomic energy. Radiation pushes outwards against gravity, holding the star open as a glowing ball of gas. As stars age, more and more of the atoms are fused, creating heavier and heavier elements, and eventually the fuel starts to run out. Without the outwards push, the balance is tipped in favour of gravity and the star begins to collapse. For small stars, such as the Sun, the collapse is incomplete, and repelling forces manage to hold the last glowing embers open as a white dwarf star. For a white dwarf star that’s larger than 1.4 times the mass of the Sun – known as the Chandrasekhar limit – these forces are insufficient. The star continues to crunch inwards, forming a dense neutron star or a black hole.
2 SUPERMASSIVE BLACK HOLES DON’T DESTROY EVERYTHING NEARBY
Actively feeding supermassive black holes are some of the most violent places in the universe, and quasars devour the equivalent of tens to thousands of Suns each year. Amazingly, though, the galaxies that surround them don’t disappear into the abyss. Despite their frightening reputation, black holes don’t actually behave that differently to other massive objects in the universe, unless you get too close. Just as Earth will not spontaneously crash into the Sun, objects in stable orbits around black holes are in no danger of being swallowed.
3 BLACK HOLES SLOW THE FLOW OF TIME
To an outside observer, an object falling into a black hole appears to slow down before stopping, caught in suspended animation at the boundary.
4 A BLACK HOLE REVEALS NO CLUES ABOUT WHAT IT’S SWALLOWED
As matter enters a black hole, it’s stretched, pulled and eventually shredded. Even if something were to leak out, it would bear no resemblance to what went in.
5 THEY HAVE NO SIZE LIMIT
In theory, black holes continue to grow in size indefinitely, but just how large they are able to get depends on their local environment.
6 AROUND THE SAME MASS AS THE SOLAR SYSTEM
Supermassive black holes contain the mass of at least 100,000 Suns compressed into a space that’s around the same size as our Solar System.
