The first black hole ever discovered by humans has turned out to be even bigger than first thought, according to new research.
Cygnus X-1 was discovered after a pair of Geiger counters were carried on board a sub-orbital rocket launched from New Mexico.
It was the subject of a famous scientific bet between Stephen Hawking and Kip Thorne in 1974 in which Professor Hawking waged a four years subscription to Private Eye versus one year's subscription to Penthouse that it wasn't a black hole.
Hawking conceded in 1990 and now astronomers reporting in the journal Science have provided more information on that says that Cygnus X-1 in fact contains the most massive stellar-mass black hole ever detected without the use of gravitational waves.
"If we can view the same object from different locations, we can calculate its distance away from us by measuring how far the object appears to move relative to the background," said lead researcher, Professor James Miller-Jones.
"If you hold your finger out in front of your eyes and view it with one eye at a time, you'll notice your finger appears to jump from one spot to another. It's exactly the same principle," added Prof Miller-Jones, from Curtin University and the International Centre for Radio Astronomy Research (ICRAR).
"Over six days we observed a full orbit of the black hole and used observations taken of the same system with the same telescope array in 2011," the professor said.
"This method and our new measurements show the system is further away than previously thought, with a black hole that's significantly more massive."
Fascinating stuff. The new discovery of the black hole's true size has made astronomers re-think how they may actually form in the first place.
The research's co-author Professor Ilya Mandel from Monash University said: "Stars lose mass to their surrounding environment through stellar winds that blow away from their surface. But to make a black hole this heavy, we need to dial down the amount of mass that bright stars lose during their lifetimes."
He added: "The black hole in the Cygnus X-1 system began life as a star approximately 60 times the mass of the Sun and collapsed tens of thousands of years ago," he said. "Incredibly, it's orbiting its companion star - a supergiant - every five and a half days at just one-fifth of the distance between the Earth and the Sun.
"These new observations tell us the black hole is more than 20 times the mass of our Sun, a 50% percent increase on previous estimates."
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