A black hole … Cygnus X1

At www.dailygalaxy.com/my_weblog/2011/06/cygnus-x-1-a-black-hole-harvard-sm… is one of those posts where you wonder if the use of proof is a bit stretched, but never mind, apparently some people think Hawking has lot a bet he made with Caltech astrophysicist Kip Thorn on Cygnus X1. Hawking said it was a neutron star and Thorn was sure it was a black hole. It seems Thorn has won himself a year's subscription to Penthouse magazine as astrophysicists claim to have measured the distance and mass of the star. It is said to be 6050 light years away and is 19 times more massive than our Sun. The mass is said to be greater than that required for a black hole, therefore it has a black hole – but are we all sure about that?