Cygnus X-1

 

I was aware of Cygnus X-1 in my teenage years because of Rush's songs based on it, but at that point I had no idea what a black hole was. By the time I'd started teaching about black holes, I'd forgotten about Cygnus X-1. So belatedly I have found out where it is in the sky, although I have no equipment for seeing it. It is X instead of a Greek letter because it is an X-ray source. It turns out to be the object about which Kip Thorne and Stephen Hawking had their bet, Thorne winning when it was settled on as the first observed black hole.