Illustration of Cygnus X-1
Cygnus X-1 is located near large active regions of star formation in the Milky Way. An artist's illustration 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. The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets.
(Credit: NASA/CXC/M.Weiss)

Chandra X-ray Image of Cygnus X-1
Over three decades ago, Stephen Hawking placed -- and eventually lost - a bet against the existence of a black hole in Cygnus X-1. Today, astronomers are confident the Cygnus X-1 system contains a black hole. In fact, a team of scientists has combined data from radio, optical, and X-ray telescopes including Chandra to determine the black hole's spin, mass, and distance more precisely than ever before. With these key pieces of information, the history of the black hole has been reconstructed. This new information gives astronomers strong clues about how the black hole was born, how much it weighed, and how fast it was spinning. This is important because scientists still would like to know much more about the birth of black holes.
(Credit: NASA/CXC)

Wide Field Image of Cygnus X-1
Cygnus X-1 is a black hole about 15 times the mass of the Sun in orbit with a massive blue companion star. Using optical observations of the companion star and its motion around its unseen companion, the team made the most precise determination ever for the mass of Cygnus X-1, of 14.8 times the mass of the Sun. It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.
(Credit: DSS)

Cygnus X-1 with Scale Bar
(Credit: X-ray: NASA/CXC; Optical: DSS; Illustration: NASA/CXC/M.Weiss)