Most Massive Black Holes Discovered

As technology and observing techniques improve, we can measure the movements of stars and gas in galaxies farther away with more precision. Using more advanced techniques and instruments, Karl Gebhardt and graduate student Jeremy Murphy of The University of Texas at Austin have discovered a pair of black holes with about 10 billion solar masses each in galaxies over 300 million light years away!

They had to combine data from several telescopes including the 8 meter Gemini Telescope in Hawaii, the 10 meter Keck Telescope in Hawaii and the Mitchell Spectrograph on the 2.7 meter telescope at McDonald Observatory in Texas. By measuring how fast stars and gas are orbiting the black hole, you can calculate the mass of the black hole.

In spite of the amazingly large mass of the black holes, they are not large on the cosmic scale. The event horizons of these beasts (the point of no return where not even light can escape) is about 200 times the distance from the Earth to the Sun (commonly called an astronomical unit, or a.u.). And we don't need to worry about these guys...they are both over 300 million light years away (and we have a pretty good size black hole much closer to us at the center of our galaxy which we are happily orbiting right now and don't have to worry about it either!)

These black holes probably formed by the mergers of black holes in smaller galaxies and astronomers are very interested in figuring out the details of how these super massive black holes form. These black holes may be the same ones that powered quasars in the early universe but have run out of the supply of gas and dust that powered quasars billions of years ago.

Now when I first read this story it jogged a circuit in my brain that recalled a story from a couple of years ago that astronomers had found evidence that there is a limit to the size of the largest black holes. Sure enough, I quickly found that article again. Priyamvada Natarajan, an associate professor of astronomy and physics at Yale University and a fellow at the Radcliffe Institute for Advanced Study, found an upper limit for the mass of black holes at (drum roll, please!) 10 billion solar masses!

Now I am sure Gebhardt and Murphy are already hard at work looking at more galaxies and trying to find even more massive black holes and they would love to break the 10 billion solar mass rule and make astronomers rethink their ideas on black hole formation and evolution!

Reprinted with permission from the Half-Astrophysicist Blog.