Most observed black holes are either "big," ranging from between 10 and 100 times the mass of our Sun, or "colossal", which are over a million times the mass of our Sun; for the first time researchers effectively measured a medium sized black hole.
Researchers confirmed the existence of a black hole 400 times the mass of our Sun in a galaxy 12 million light years away, the College of Computer, Mathematical, and Natural Sciences reported.
"Objects in this range are the least expected of all black holes," Co-author Richard Mushotzky, a UMD astronomy professor said. "Astronomers have been asking, do these objects exist or do they not exist? What are their properties? Until now we have not had the data to answer these questions."
The black hole is not the first to be measured, but it is the first to recieve such a precise measurement, possibly opening the door for a new class of black holes.
A black hole has a mass so dense that even light cannot escape. Even though they are invisible researchers can track them by looking at how their gravitational pull affects nearby objects. Matter being pulled into black holes gathers around it and produces friction and light, making black holes some of the universe's brightest objects. In the past researchers have observed hundreds of objects that they thought were intermediate-mass black holes, but were never able to measure their mass.
"For reasons that are very hard to understand, these objects have resisted standard measurement techniques," Mushotzky said.
In 1991 a NASA satellite telescope detected X-rays coming from a bright object in the Messier 82 galaxy, dubbed M82 X-1. Between 2004 and 2010 NASA's Rossi X-Ray Timing Explorer (RXTE) looked at the object about 800 times, recording each emitted radio particle. Astronomy graduate student Dheeraj Pasham mapped the intensity and wavelength of these X-rays in a sequence.
Among the matter circling around the black hole the researchers observed two flares of light showing a rhythmic patter of pulses; one occurring 5.1 times per second and the other 3.3. times per second.
If these bears were rhythms they would produce a specific syncopated rhythm. For example the Beatler's White Album: "Mean Mister Mustard sleeps in the park, shaves in the dark, try'na save paper." Those lyrics represent a 3:2 beat; astronomers can use a 3:2 pattern of light oscillation to measure the black hole's mass. The team used this technique to determine M82 X-1 is 428 times the mass of the sun, making it an intermediate star.
"We needed to confirm their existence observationally first," Pasham said. "Now the theorists can get to work."
