Question: how black holes created

Daniel Parsons answered on 10 Nov 2014:

Black holes form when the centre of a very big star collapses in upon itself. If you compress a star into a smaller and smaller volume then its gravitational pull becomes bigger and bigger. The idea was first conceived in the 18th century by the geologist John Mitchell. He realized that if you could compress the Sun down by several orders of magnitude, it would have a gravity so strong that you’d need to be going faster than the speed of light to escape it!
This collapse of a star also causes a supernova, or an exploding star, that blasts part of the star into space. If they happen close enough to us we can see them in the nigh sky. In the year 1006 a large supernova occurred that was over 10 times as bright as anything else in the night sky (apart from the moon!), this was the brightness event ever recorded in human history!