These stars have such high gravity that, when their cores collapse, they get compressed into a single point called a singularity.
The gravity of a singularity is so strong that nothing at close range can escape - not even light! Everything, it seems, is sucked in and destroyed.
Super-massive black holes have been found the centre of every surveyed galaxy* - including our own! But fortunately for us, we are 20,000 light years* from our galaxy's centre, so the black hole's gravity is no threat to us.