NASA discovers details of black hole`s origin

Scientists has discovered new details about the birth of a famous black hole that took place millions of years ago.

Updated: Nov 18, 2011, 13:48 PM IST

Washington: A team of scientists has discovered new details about the birth of a famous black hole that took place millions of years ago using data from NASA’s Chandra X-ray Observatory as well as from radio, optical and other X-ray telescopes.

Over three decades ago, Stephen Hawking placed – and eventually lost – a bet against the existence of a black hole in Cygnus X-1.

Today, astronomers are confident the Cygnus X-1 system contains a black hole, and with these latest studies they have remarkably precise values of its mass, spin, and distance from Earth.

“This new information gives us strong clues about how the black hole was born, what it weighed and how fast it was spinning,” said mark Reid of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass, one of the researcher.

“This is exciting because not much is known about the birth of black holes,” he added.

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.

Using X-ray data from Chandra, the Rossi X-ray Timing Explorer, and the Advanced Satellite for Cosmology and Astrophysics, the team was 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.

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 times the mass of the Sun. It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.

“It is amazing to me that we have a complete description of this asteroid-sized object that is thousands of light years away. This means astronomers have a more complete understanding of this black hole than any other in our Galaxy,” said Lijun Gou, also from CfA, who led one of the three studies.

The team also announced that they have made the most accurate distance estimate yet of Cygnus X-1 using the National Radio Observatory``s Very Long Baseline Array (VLBA). The new distance is about 6,070 light years from Earth. This accurate distance was a crucial ingredient for making the precise mass and spin determinations.

The findings appeared in the November 10th issue of The Astrophysical Journal.