New look at first black hole detected shows it is bigger than expected

WASHINGTON: A fresh examination has revealed new details about the first black hole ever detected, which was spotted in 1964 and became the subject of a friendly wager between renowned scientists, including that it is bigger than previously known.

Researchers said on Thursday (Feb 18) that new observations of the Cygnus X-1 black hole, orbiting in a stellar marriage with a large and luminous star, showed it is 21 times our sun's mass, about 50 per cent more massive than previously believed.

While it is still one of the closest-known black holes, they found it is somewhat farther away than previously calculated, at 7,200 light years - the distance light travels in a year - 9.5 trillion km from Earth.

Black holes are extremely dense, with gravitational pulls so ferocious not even light escapes. Some - the "supermassive" black holes - are immense, like the one at our Milky Way galaxy's centre four million times the sun's mass. Smaller "stellar-mass" black holes possess the mass of a single star.

Cygnus X-1 is the Milky Way's largest-known stellar-mass black hole and among the strongest X-ray sources seen from Earth, said astronomer James Miller-Jones of Curtin University and the International Centre for Radio Astronomy Research in Australia, who led the study published in the journal Science.

​This black hole spins so rapidly, nearly light speed, that it approaches the maximum rate envisioned under physicist Albert Einstein's theory of general relativity, Miller-Jones added.

It devours material blowing from the surface of the companion star it tightly orbits, a "blue supergiant" about 40 times our sun's mass. It started its existence four million to five million years ago as a star up to 75 times the sun's mass and collapsed into a black hole a few tens of thousands of years ago.

The research included data from the Very Long Baseline Array radio telescope comprising 10 US observation stations.

After Cygnus X-1 was first tabbed as a black hole, a wager was made between physicists Stephen Hawking, who bet against it being one, and Kip Thorne, who bet it was. Hawking eventually conceded, owing Thorne a Penthouse magazine subscription.

"Indeed, I did not have any wagers riding on these findings," Miller-Jones said.