Starmus

On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box.  Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist's illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system.  Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star.  New studies with data from Chandra and several other telescopes have determined the black hole's spin, mass, and distance with unprecedented accuracy.

Black holes and other star remnants

Imagine a dog owner with a reflective vest and a black dog without one. In the dark we can see how the dog owner moves, but not the dog. That’s how black holes work, too.