Massive Black Hole Is A Real Heavyweight
November 29, 2012

Astronomers Measure Most Massive Black Hole Yet

Lee Rannals for - Your Universe Online

Astronomers have measured the mass of what may be the most massive black hole observed so far by using the Hobby-Eberly Telescope at The University of Texas at Austin's McDonald Observatory.

The black hole makes up 14 percent of its galaxy's mass, rather than the usual 0.1 percent, according to the study published in the journal Nature.

NGC 1277 is about 220 million light-years away from Earth, and is just ten percent the size and mass of our own Milky Way. Although it is a small galaxy, the black hole in its heart is more than 11 times as wide as Neptune's orbit around the Sun.

"This is a really oddball galaxy," said team member Karl Gebhardt of The University of Texas at Austin. "It's almost all black hole. This could be the first object in a new class of galaxy-black hole systems."

Ultimately, the researchers using the telescope are hoping to gain a better understanding of how black holes and galaxies form and grow together.

"At the moment there are three completely different mechanisms that all claim to explain the link between black hole mass and host galaxies' properties. We do not understand yet which of these theories is best," said lead author Remco van den Bosch.

Astronomers know the mass of fewer than 100 black holes in galaxies, but measuring these cosmic objects is difficult and time-consuming. The team developed the HET Massive Galaxy Survey to dwindle down the number of galaxies to follow up on.

"When trying to understand anything, you always look at the extremes: the most massive and the least massive," Gebhardt said. "We chose a very large sample of the most massive galaxies in the nearby universe," to learn more about the relationship between black holes and their host galaxies.

The team has studied 700 of their 800 galaxies with HET, and Gebhardt said the telescope works best when the galaxies are spread all across the sky.

The astronomers wrote in the paper that they zeroed in on the top six most massive galaxies, and found that NGC 1277 had already been photographed by Hubble Space Telescope. This image helped to provide measurements of the galaxy's brightness at different distances from its center.

When the team combined HET data and various models run through a supercomputer, they saw that the black hole had a mass of 17 billion Suns.

"The mass of this black hole is much higher than expected," Gebhardt concluded. "It leads us to think that very massive galaxies have a different physical process in how their black holes grow."