Question: I have just been watching a very interesting programme on the television about scientists who are studying the super massive black hole in the centre of our Milky Way galaxy. It was stated that that black holes are formed when huge stars die and collapse in on themselves. Taking the super massive black hole in the centre of the Milky Way galaxy as an example, is it possible for scientists to run a retrospective analysis to ascertain the magnitude of the star which died and caused the black hole to form. — David
Answer: Yes. Computer modelling of the evolution of very massive stars have shown us that a star with a mass greater than 20 times the mass of our Sun may ultimately become a black hole. Once the star runs out of fuel to drive its nuclear engine gravity takes over, compressing the star which ultimately collapses. This collapse results in a supernova, which expels the outer parts of the star but leaves the core to collapse even more. If the core has a mass which is greater than 2.5 times the mass of our Sun, gravity takes over and causes the core to collapse to form a black hole.