Cygnus X-1
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Cygnus X-1 (often abbreviated to Cyg X-1) is an X-Ray Source in the constellation Cygnus, and considered to be a black hole. It is a high-mass X-ray binary, with the optical counterpart (HDE 226868) being a variable 8.9 magnitude star (visible with good binoculars in good observing conditions) at right ascension 19 h 56.5 min and declination of 35 deg 4 min (for 1950 epoch).
Tom Bolton identified Cygnus X-1 as a black hole in 1971 using the facilities of the David Dunlap Observatory at the University of Toronto.
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[edit] Star System
Cyg X-1 is a binary star that contains an O9-B0 supergiant (with a surface temperature of 31,000 kelvins) and a compact object. The mass of the supergiant is approximately 20–40 solar masses. The compact object has a mass of 20–35 solar masses; as the largest possible mass of a neutron star can not exceed three solar masses, it is thought to be a black hole. The X-rays are produced in an accretion disk and in the focused companion wind corona that is formed by matter flowing from the supergiant into the black hole. Cygnus X-1 is the brightest persistent source of hard X-rays (E > 20 keV) in the sky. The distance to Cygnus X-1 is about 2500 parsecs or 8000 ly.
[edit] HDE 226868
HDE 226868 is a blue super giant in orbit around the (probable) black hole Cygnus X-1. Matter is being stripped off HDE 226868 by the black hole's powerful gravity.
[edit] Stephen Hawking and Kip Thorne
Cygnus X-1 was the subject of the bet between physicists Stephen Hawking and Kip Thorne, in which Hawking bet against the existence of black holes in the region. Hawking later described this as an "insurance policy" of sorts. To quote from his book, A Brief History of Time, "This was a form of insurance policy for me. I have done a lot of work on black holes, and it would all be wasted if it turned out that black holes do not exist. But in that case, I would have the consolation of winning my bet, which would win me four years of the magazine Private Eye. If black holes do exist, Kip will get one year of Penthouse. When we made the bet in 1975, we were 80% certain that Cygnus was a black hole. By now, I would say that we are about 95% certain, but the bet has yet to be settled." (1988) According to the updated 10th anniversary edition of A Brief History of Time, Hawking has conceded the bet "to the outrage of Kip's liberated wife" due to subsequent observational data in favour of black holes.
[edit] Musical Connections
In 1977 Rush recorded a song about a fictional space voyage to Cygnus X-1. The song appears on the album A Farewell to Kings. A followup, "Cygnus X-1 Book II: Hemispheres" is featured on the 1978 Rush album Hemispheres, which explores the possibilities on the other side of Cygnus X-1, placing a much greater emphasis on symbolism. Bethany Curve's 1998 album Gold also included a track entitled "Cygnus X-1". In 2001, Weezer demoed an instrumental song called "Cygnus X-1" for their fourth album Maladroit. Technical metal band Alarum also featured a song titled "Cygnus X-1" on their 2004 album Eventuality.... A line in The Homosexuals' song "Neutron Lover" mentions Cygnus X-1.
