July 21, 2012
Four Black Hole Candidates Discovered
redOrbit Staff & Wire Reports - Your Universe Online
Researchers from a Japanese university have discovered intermediate-mass black hole (IMBH) candidates at the center of the Milky Way, the National Astronomical Observatory of Japan (NAO) announced on Friday.Tomoharu Oka, an Associate Professor at Keio University, and colleagues used radio telescopes to locate four black hole candidates approximately 30,000 light-years from the solar system, located in the direction of the constellation Sagittarius, the NAO said. Those candidates were described by Oka as "warm, dense (more than 50 degrees Kelvin, more than 10,000 hydrogen molecules per cubic centimeter)” masses of molecular gas.
Three of those masses have been expanding, which research suggests was caused by supernova explosions. The largest of those is believed to have been equal to 200 supernova explosions, while the age of the gas masses was estimated to be roughly 60,000 years old, leading the researchers to surmise that a massive star cluster could be buried within one of the black hole candidates.
"The mass of the cluster (more than 100,000 times the mass of the sun) is comparable to the largest star cluster found in the Milky Way Galaxy," the NAO said in their July 20 press release. "It is thought that IMBHs are formed within such huge star clusters. Eventually, IMBHs born near the center of the Milky Way Galaxy form/expand into a supermassive black hole at the nucleus of the galaxy."
As part of their research, which lasted from 2005 to 2010 and is detailed in the Astrophysical Journal Supplement Series, Oka and his associates used the ASTE 10 m telescope in Chile's Atacama Desert to detect emission lines at wavelengths of 0.87 mm originating from carbon monoxide molecules in an area of several degrees, including the center of the galaxy. They compared that data with that of emission lines at wavelengths of 2.6 mm, emitted from carbon monoxide molecules in the same area.
"When intensity values of emission lines at different wavelengths, emitted from carbon monoxide molecules, are compared, it is possible to estimate temperature and density of molecular gas," the NAO said. "In this way, the research team succeeded in drawing detailed distribution maps of 'warm, dense' molecular gas of more than 50 degrees Kelvin and more than 10,000 hydrogen molecules per cubic centimeter at the center of the Milky Way Galaxy for the first time ever."
Oka called the results "astonishing," adding that the four "clumps" of molecular gas were each moving at speeds exceeding 100km per second, and that it is believed that one of them is home to a supermassive black hole believed to be as much as 4 million times the mass of the sun.