Cygnus X-1

8.95

Apparent Mag

6,070

Distance (ly)

O9.7Iab

Spectral Type

31,000

Temperature (K)

Cygnus X-1 is the most famous stellar-mass black hole, discovered in 1964. Its visible companion is a blue supergiant star.

Stellar Data

Apparent Magnitude8.95

Absolute Magnitude-6.5

Distance6,070 light-years

Spectral TypeO9.7Iab

Temperature31,000 K

Luminosity300,000 L☉

Radius22 R☉

Mass40.6 M☉

Right Ascension19h 58m 21.7s

Declination+35° 12′ 05.8″

ConstellationCygnus

Cygnus X-1 was one of the first objects identified as containing a black hole
Stephen Hawking and Kip Thorne had a famous bet about whether it was a black hole
The black hole has about 21 solar masses