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| Artist's conception of Cygnus X-1: black holes attract matter froma companion star (right) gets hot, rotating disk |
For the first time, astronomers have produced a completedescription of a black hole, the concentration of mass so dense that even light can not escape the strong gravitational pull. Their exact measurements has allowed them to reconstruct the history ofthe object of his birth about six million years ago.
Using several telescopes, both ground-based and in orbit, scientists have unraveled the mystery of a long object called Cygnus X-1, a well-known binary star system was found to be strong X-ray emitting nearly half a century ago. This system consists of a black hole and companion star from which the black hole is drawing matter. Efforts of the scientists' produce the most accurate measurements ever of black hole mass and spin rate.
"Because there is no other information can escape from a black hole, knowing its mass, spin, and electric charge gives a full explanation about it," said Mark Reid, of the Harvard-Smithsonian Center for Astrophysics (CfA). "This accusation of black holes is almost zero, so that measuring the mass and spin to make us a complete description," he added.
Although the Cygnus X-1 has been studied intensively since its discovery, previous attempts to measure the mass and spin suffers from a lack of precise measurements of the distance from Earth. Reid led a team that used Very Long Baseline Array of the National Science Foundation (VLBA), the continent-wide radio telescope system, to make direct trigonometric measurement of distance. They VLBA observations give a distance of 6070 light-years, whereas previous estimates have ranged 5800-7800 light-years away.
Armed with the measurements, just the right distance, the scientists using the Chandra X-Ray Observatory, Rossi X-Ray Timing Explorer, Advanced Satellite for Cosmology and Astrophysics, and visible-light observations made during more than two decades, calculates that the black hole Cygnus in the X-1 is almost 15 times more massive than our Sun and rotate more than 800 times per second.
"This new information gives us strong clues about how the black hole was born, what were weighed and how fast it is spinning," said Reid. "Getting a good measurement of distance is very important," added Reid.
"We now know that Cygnus X-1 is one of the biggest black hole in Milky Way stars," said Jerry Orosz, from San Diego State University. "This black hole spin as fast as anything we've ever seen," he added.
In addition to measuring the distance, VLBA observations, made during 2009 and 2010, were also measured movement of Cygnus X-1 through our galaxy. That movement, the scientists said, is too slow for the black hole has been generated by supernova explosions. As the explosion will give the object a "kick" for higher speeds.
"There is a suggestion that black holes can be formed without a supernova explosion, and our results support the suggestion that," Reid said.
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