Light Pulses Illuminate Rare Intermediate Black Hole

There are nearly 100 million black holes within our galaxy alone. Most of these range from about 10 times to 100 times the mass of our sun and are the remnants of dying stars while others are supermassive black holes located in the centers of galaxies. Yet scattered across the universe are some more mysterious black holes of an intermediate size and now, astronomers have gotten a closer look at one with the help of light pulses.

"Objects in this range are the least expected of all black holes," said Richard Mushotzky, co-author of the new study, in a news release. "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 in question is about 400 times the mass of our sun and is located in a galaxy 12 million light years from Earth. It's the most precisely measured intermediate black hole to date. Astronomers first examined the black hole, called M82 X-1, between 2004 and 2010 with the help of NASA's Rossi X-Ray Timing Explorer (RXTE) satellite telescope. Among the material circling the black hole, the astronomers spotted two repeating flares of light.

It's these flares of light that helped researchers realize that they were actually dealing with an intermediate black hole. The two light oscillations were like two dust motes stuck in the grooves of a vinyl record spinning on a turntable. If the oscillations were musical beats, they would produce a specific syncopated rhythm. In this case, the astronomers used a 3:2 oscillation of light to measure the black hole's mass.

In the end, the researchers found that M82 X-1 is about 428 times the mass of the sun, give or take 105 solar masses. Currently, they're not sure exactly how this class of black holes formed. However, the new findings do provide astronomers with a good example of an intermediate black hole. Currently, they're hoping to continue finding more of these black holes to learn a bit more about them in the future.

The findings are published in the journal Nature.