What is Cygnus X-1?
'''Cygnus&nbsp;X-1''' (abbreviated '''Cyg&nbsp;X-1''') is a well-known galactic [[X-ray]] source. It is thought to be a [[black hole]] in the [[constellation]] [[Cygnus (constellation)|Cygnus]]. [[File:Chandra image of Cygnus X-1.jpg|thumb|[[Chandra X-ray Observatory]] image of Cygnus X-1.]] It was discovered in 1964 during a [[rocket]] flight, and is one of the strongest X-ray sources seen from [[Earth]]. Cygnus&nbsp;X-1 was the first X-ray source accepted as a black hole. It is among the most studied [[astronomical object]]s in its class. The compact object is estimated to have a mass about 14.8 times the [[Solar mass|mass of the Sun]].<ref>Orosz, Jerome ''et al'' 2011. The mass of the black hole in Cygnux X-1. ''Astrophysical Journal''. '''742''' (2). [http://iopscience.iop.org/article/10.1088/0004-637X/742/2/84/meta;jsessionid=F49AAB1667A4F3151C23FB3320C38930.c3.iopscience.cld.iop.org]</ref> It is too small to be any known kind of normal star, or other likely object besides a black hole. If so, the radius of its [[event horizon]] is about {{val|44|ul=km}}. == References == {{reflist}} {{-}} {{physics-stub}} [[Category:Binary stars]] [[Category:Black holes]]