About black holes – making the unbelievable believable
As far as black holes are concerned, my mind is not unlike a black hole. It can swallow up information about them without any real glimmers of understanding emerging. I must confess that I have been rather sceptical about their existence, particulary the idea that there is a supermassive black hole at the centre of our galaxy. So I always knew that our recent talk on “Black holes and how to find them” was going to be a bit of a challenge. The speaker was Malcolm McCallum of Queen Mary College London who has an impressive CV and can count Stephen Hawking and Martin Rees , Astronomer Royal, as contemporaries. I can’t claim to have followed all the details of his talk but it did give me not just one but two “Eureka!” moments.
Eureka moments
The first Eureka moment was his statement that a black hole will not suck everything towards it. If an object is in a stable orbit around a black hole, then it will stay in that stable orbit in just the same way that the Earth can stay in orbit around the Sun. Phew ! that helps to explain why the whole Milky Way is not in the process of being remorsely pulled into the black hole at its centre. You don’t want anything to disturb that stable orbit though ; then it could be a different story. The second light bulb moment was when he showed a wonderful composite image taken over several years looking towards the centre of our galaxy. This is the image used to illustrate this posting.
The region was imaged at yearly intervals between 1995 and 2010 and the actual locations of seven stars picked out (S0-1, S0-2 etc shown in the key). This gave enough data to compute the continuation of their paths. It does seem to show that the stars are all in orbit around the same something which does not show up in any image. The conclusion is that they are orbiting a black hole. It’s a beautiful picture, both aesthetically and for elegantly and simply illustrating its point.
Talk given by Emeritus Professor Malcolm McCallum Queen Mary College London
Post written by Katherine Rusbridge
Oct 2013