Astronomers have discovered for the first time the complete description of a black hole which allowed them to reconstruct the history of the object from its birth around six million years ago.

The scientists used several telescopes, both ground-based and in orbit, to unravel the mysteries about the object called Cygnus X-1, a famous binary-star system found to be strongly emitting X-rays almost half a century ago. The scientists' efforts yielded the most accurate measurements ever of the black hole's mass and spin rate.

"Because no other information can escape from a black hole, knowing its mass, spin, and electrical charge gives a complete description of it," said Mark Reid, of the Harvard-Smithsonian Center for Astrophysics (CfA). "The charge of this black hole is nearly zero, so measuring its mass and spin make our description complete," he added

Since its discovery, scientists have studied the Cygnus X-1 intensely since its discovery but because of lack of a precise measurement of its distance from Earth previous attempts to measure its mass and spin was not successful.

With the new study, 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 and their VLBA observations provided a distance of 6070 light-years. Previous estimates had ranged from 5800-7800 light-years.

With the new, precise distance measurement, scientists used the Chandra X-Ray Observatory, the Rossi X-Ray Timing Explorer, the Advanced Satellite for Cosmology and Astrophysics, and visible-light observations made over more than two decades, to calculate the black hole in Cygnus X-1. They found out that it is nearly 15 times more massive than our Sun and is spinning more than 800 times per second.

"This new information gives us strong clues about how the black hole was born, what it weighed and how fast it was spinning," Reid said. "Getting a good measurement of the distance was crucial," Reid added.

"We now know that Cygnus X-1 is one of the most massive stellar black holes in the Milky Way," said Jerry Orosz, of San Diego State University. "It's spinning as fast as any black hole we've ever seen," he added.

The study by on Cygnus X-1 by Reid, Orosz, and Lijun Gou, also of CfA, were the lead authors of three papers on Cygnus X-1 was published in the Astrophysical Journal Letters.