An international team of astronomers has discovered a black hole that could shake the foundations of current models of galaxy evolution.
The unusual black hole has been detected in a lenticular galaxy known as NGC 1277 with the Hobby-Eberly Telescope (HET) at the McDonald observatory in Texas.
The lenticular galaxy NGC 1277 lies about 220 million light-years away in the constellation Perseus. It is only ten percent the size and mass of our Milky Way Galaxy. Despite galaxy’s diminutive size, the supermassive black hole at its heart weighs in at roughly 17 billion solar masses and is more than 11 times as wide as Neptune’s orbit around the Sun.
“This is a really oddball galaxy,” said Dr Karl Gebhardt of the University of Texas at Austin, co-author of a study published in the journal Nature. “It’s almost all black hole. This could be the first object in a new class of galaxy-black hole systems.” Furthermore, the most massive black holes have been seen in giant blobby galaxies called “ellipticals,” but this one is seen in a relatively small lens-shaped galaxy.
The study’s endgame is to better understand how black holes and galaxies form and grow together, a process that isn’t well understood.
“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 Dr Remco van den Bosch of the Max Planck Institute for Astronomy in Heidelberg, Germany.
Astronomers know the mass of fewer than 100 black holes in galaxies. But measuring black hole masses is difficult and time-consuming. So the team developed the HET Massive Galaxy Survey to winnow down the number of galaxies that would be interesting to follow up on.
“When trying to understand anything, you always look at the extremes: the most massive and the least massive,” Dr 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.
In the study, the team zeroes in on the top six most massive galaxies. They found that one of those, NGC 1277, had already been photographed by NASA’s Hubble Space Telescope. This provided measurements of the galaxy’s brightness at different distances from its center. When combined with HET data and various models run via supercomputer, the result was a mass for the black hole of 17 billion Suns.
“The mass of this black hole is much higher than expected,” Dr Gebhardt said, “it leads us to think that very massive galaxies have a different physical process in how their black holes grow.”
Bibliographic information: Remco C. E. van den Bosch et al. 2012. An over-massive black hole in the compact lenticular galaxy NGC 1277. Nature 491 (7426): 729; doi: 10.1038/nature11592