Nav: Home

VLBA observations key to 'complete description' of black hole

November 17, 2011

For the first time, astronomers have produced a complete description of a black hole, a concentration of mass so dense that not even light can escape its powerful gravitational pull. Their precise measurements have allowed them to reconstruct the history of the object from its birth some six million years ago.

Using several telescopes, both ground-based and in orbit, the scientists unravelled longstanding mysteries about the object called Cygnus X-1, a famous binary-star system discovered to be strongly emitting X-rays nearly a half-century ago. The system consists of a black hole and a companion star from which the black hole is drawing material. 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.

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.

Armed with the new, precise distance measurement, scientists using 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, calculated that the black hole in Cygnus X-1 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.

In addition to measuring the distance, the VLBA observations, made during 2009 and 2010, also measured Cygnus X-1's movement through our Galaxy. That movement, the scientists, said, is too slow for the black hole to have been produced by a supernova explosion. Such an explosion would have given the object a "kick" to a much higher speed.

"There are suggestions that this black hole could have been formed without a supernova explosion, and our results support those suggestions," Reid said.

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

The VLBA, dedicated in 1993, uses ten, 25-meter-diameter dish antennas distributed from Hawaii to St. Croix in the Caribbean. It is operated from the NRAO's Domenici Science Operations Center in Socorro, NM. All ten antennas work together as a single telescope with the greatest resolving power available to astronomy. This unique capability has produced landmark contributions to numerous scientific fields, ranging from Earth tectonics, climate research, and spacecraft navigation to cosmology.

Ongoing upgrades in electronics and computing have enhanced the VLBA's capabilities. With improvements now nearing completion, the VLBA will be as much as 5,000 times more powerful as a scientific tool than the original VLBA of 1993.


The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

National Radio Astronomy Observatory

Related Black Hole Articles:

Scientists make waves with black hole research
Scientists at the University of Nottingham have made a significant leap forward in understanding the workings of one of the mysteries of the universe.
Collapsing star gives birth to a black hole
Astronomers have watched as a massive, dying star was likely reborn as a black hole.
When helium behaves like a black hole
A team of scientists has discovered that a law controlling the bizarre behavior of black holes out in space -- is also true for cold helium atoms that can be studied in laboratories.
Star in closest orbit ever seen around black hole
Astronomers have found evidence of a star that whips around a likely black hole twice an hour.
Tail of stray black hole hiding in the Milky Way
By analyzing the gas motion of an extraordinarily fast-moving cosmic cloud in a corner of the Milky Way, Astronomers found hints of a wandering black hole hidden in the cloud.
Hubble gazes into a black hole of puzzling lightness
The beautiful spiral galaxy visible in the center of the image is known as RX J1140.1+0307, a galaxy in the Virgo constellation imaged by the NASA/ESA Hubble Space Telescope, and it presents an interesting puzzle.
Clandestine black hole may represent new population
Astronomers have combined data from NASA's Chandra X-ray Observatory, the Hubble Space Telescope and the National Science Foundation's Karl G.
When will a neutron star collapse to a black hole?
Astrophysicists from Goethe-University Frankfurt have found a simple formula for the maximum mass of a rotating neutron star and hence answered a question that had been open for decades.
Behemoth black hole found in an unlikely place
Astronomers have uncovered a near-record breaking supermassive black hole, weighing 17 billion suns, in an unlikely place: in the center of a galaxy in a sparsely populated area of the universe.
Behemoth black hole found in an unlikely place
Astronomers have uncovered one of the biggest supermassive black holes, with the mass of 17 billion Suns, in an unlikely place: the centre of a galaxy that lies in a quiet backwater of the Universe.

Best Science Podcasts 2017

We have hand picked the best science podcasts for 2017. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: Radiolab

Radiolab Presents: Anna in Somalia
This week, we are presenting a story from NPR foreign correspondent Gregory Warner and his new globe-trotting podcast Rough Translation. Mohammed was having the best six months of his life - working a job he loved, making mixtapes for his sweetheart - when the communist Somali regime perp-walked him out of his own home, and sentenced him to a lifetime of solitary confinement.  With only concrete walls and cockroaches to keep him company, Mohammed felt miserable, alone, despondent.  But then one day, eight months into his sentence, he heard a whisper, a whisper that would open up a portal to - of all places and times - 19th century Russia, and that would teach him how to live and love again. 
Now Playing: TED Radio Hour

Future Consequences
From data collection to gene editing to AI, what we once considered science fiction is now becoming reality. This hour, TED speakers explore the future consequences of our present actions. Guests include designer Anab Jain, futurist Juan Enriquez, biologist Paul Knoepfler, and neuroscientist and philosopher Sam Harris.