The black hole inside a neighboring galaxy, known as M87, is obese and filled with the equivalent of 6.6 billion of our suns, according to new measurements.
These supermassive black holes are relatively rare, scientists suspect, so it is surprising that such a behemoth lives relatively close by -- just 50 million light-years away.
"It's almost on top of us, relatively speaking. Fifty million light-years -- that's our backyard effectively. To have one so large, that's kind of extreme," astronomer Karl Gebhardt, with the University of Texas at Austin, told Discovery News.
The finding refines previous estimates of the size of M87's black hole, which ranged from one billion to more than six billion times the mass of the sun. The research is expected to help nail down estimates of even bigger black holes associated with ancient distant galaxies known as quasars.
"It's important to find these very large black holes. It's the upper end of the black hole mass that really matters," Gebhardt said.
Gebhardt and colleagues used a light-splitting spectrograph on the eight-meter (26-foot) Gemini North telescope in Hawaii to measure the speeds of stars orbiting M87's black hole. The motions are directly related to the gravitational pull of the black hole. The data was then used to calculate the black hole's mass.
The measurements are about 10 times better than previous observations, largely because of telescope enhancements that compensate for distortions in Earth's atmosphere, Gebhardt added.
Eventually, astronomers hope to be able to directly detect the point where matter and energy fall into a black hole, a region of space so densely packed that not even photons of light can escape its gravitational grasp. The doorstep to the black hole, from which there is no known exit, is known as the event horizon.
"Right now we have no evidence that an object is a black hole. Within a few years, we might be able to image the shadow of the event horizon," Gebhardt said.
Scientists have been wrestling to understand the relationship between black holes and host galaxies in hopes of learning more about how the universe came to exist and evolve.
Initial observations that the size of a black hole and the size of its host galaxy were matched are turning out to not always be the case.
"The relationship appears to be more complicated the closer we look," astronomer and M-87 researcher Dan Batcheldor, with the Florida Institute of Technology, told Discovery News. "In the next couple of years, we're going to start seeing more and more black holes that are atypical."
Gebhardt's research was presented on Wednesday at the American Astronomical Society meeting in Seattle and will be published in an upcoming issue of The Astrophysical Journal.