Question: How many blackholes have u seen while doing your works?

Sam Connolly answered on 16 Jun 2014:

Depends what you mean by seen! You can’t really see black holes themselves, because light can’t escape them (hence the name), but we can see the light that comes from stuff that falls into them, usually gas, which heats up as it falls in and gives off loads of light, from the optical light we can see to X-rays.

I’ve seen images and data from the light of loads of black holes (probably about fifty…), but I’ve never looked through a telescope directly and seen one, because the telescopes I use are mostly X-ray telescopes in space, so you can’t look through them! Even normal optical telescopes you can look through usually have cameras on the back instead of an eyepiece you can look through, so they can record data. Definitely the ones that are big enough to see many black holes anyway – most black holes are quite far away, so you need a big telescope to see them! I definitely wouldn’t miss the opportunity to see one directly if it came up though, so it’s a good question!