A black hole about 15 times as massive as the Sun strips gas away from a companion star in this artist's concept. The gas forms a hot, swirling disk, which emits copious X-rays. Astronomers named the system Cygnus X-1 because it was the first source of X-rays detected in Cygnus. The system is about 6,000 light-years away. [NASA/CXC/M. Weiss]