New observations of the Cygnus X1 X-ray source, reveals new unprecedented accurate measurements of the black hole's size, spin-rate, age and distance; 14,8 solar masses spinning at 48.000rpm!

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 is in close orbit with a massive, blue companion star.

Though Cygnus X-1 has been studied intensely since its discovery, previous attempts to measure its mass and spin suffered from lack of a precise measurement of its distance from Earth.Reid led a team that used the National Science Foundation's Very Long Baseline Array (VLBA), a continent-wide radio-telescope system, to make a direct trigonometric measurement of the distance. Their VLBA observations provided a distance of 6070 light-years, while previous estimates had ranged from 5800-7800 light-years.

"Because no other information can escape from a black hole, knowing its mass, spin, and electrical charge gives a complete description of it, The charge of this black hole is nearly zero, so measuring its mass and spin make our description complete," said Mark Reid from Harvard.

The scientist were able to determine the spin of Cygnus X-1 with unprecedented accuracy, showing that the black hole is spinning at very close to its maximum rate. Its event horizon -- the point of no return for material falling towards a black hole -- is spinning around more than 800 times a second or 48 000 rpm!

An independent study that compared the evolutionary history of the companion star with theoretical models indicates that the black hole was born some 6 million years ago. In this relatively short time (in astronomical terms), the black hole could not have pulled in enough gas to ramp up its spin very much. The implication is that Cygnus X-1 was likely born spinning very quickly.

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 solar masses. It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.

"We now know that Cygnus X-1 is one of the most massive stellar black holes in the Galaxy, And, it's spinning as fast as any black hole we've ever seen." said Jerome Orosz from San Diego State University

Sources: Chandra's homepage and the Australian National Radio Astronomy Observatory