EMBARGOED FOR
Astronomers have managed to wrestle one of the first supermassive black holes from the early universe onto a set of observational scales. The gravity well weighs in at one quadrillion times the heft of Earth.
That's a 1 followed by 15 zeros. Or, as astronomers like to think of it, three billion times as heavy as the Sun -- just about what was expected.
Until today's announcement, researchers had only indirect information about the masses of early black holes, which are thought to have played
key roles in the development of the first galaxies. The newly weighed black hole is compacted into a region probably no bigger than our solar system. It anchors the most distant known galaxy, a compact but bright object called a quasar that is seen as it existed more than 13 billion years ago, when the universe was just 6 percent of its present age.
Quasars are thought to be rapidly developing precursors of normal galaxies. They are extremely bright -- outshining a thousand normal galaxies -- because as gas falls toward the central black hole, it is accelerated to nearly light-speed before being swallowed. The process is not entirely efficient: Castoff energy -- radio waves, X-rays and regular light -- provides the illumination.
Quasar black holes consume a mass equal to 10 or 20 stars every year, other studies have shown. Not all the gas swallowed. Some forms knots, which collapse into stars. Eventually, when the smoke of all this activity clears, a galaxy not unlike our own Milky Way is thought to emerge.
The black hole's weight is limited by an interesting phenomenon.
"It's actually the smallest black hole that we could have seen, if we understand quasars correctly," said Chris Willott, from the National Research Council's Herzberg Institute of Astrophysics in Victoria, Canada.
The quasar, called SDSS J1148+5251, was first found as part of the Sloan Digital Sky Survey. It is consuming matter at the theoretical maximum, a threshold called the Eddington Limit. If it tried to accrete matter at a higher rate, the intense radiation would exert enough outward pressure to prevent more material from coming in.
Willott told SPACE.com that the study shows that the black hole is embedded in a vast reservoir of gas, as theory predicted. It also supports the emerging theory that black holes and galaxies
co-evolved.Observations were made with the 3.8-metre UK Infrared Telescope (UKIRT), near the summit of Mauna Kea, Hawaii. Researchers studied the speed with which ionized magnesium orbited the central black hole and compared the results with similar observations of more nearby quasars.
"This is the first time that anyone has applied the method to quasars at the edge of the observable universe," Willott said. His team plans to use the method to weigh other similarly distant quasars, as well as some that are nearer.
There are three other known quasars in the 13 billion light-year range. Willott said that because of their brightness, "we expect them all to have black holes of similar mass to the one we measured." Continued surveying by other groups is expected to turn up about 16 more quasars at similar distances in the next few years.
The results are detailed in the online edition of the Astrophysical Journal Letters.
Black Hole Birth
advertisement
advertisement
