September 6, 2013
NuSTAR Has Bagged Its First 10 Supermassive Black Holes
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April Flowers for redOrbit.com - Your Universe Online
Over the next two years, the NuSTAR team expects to find hundreds of black holes. Supermassive black holes – which are black holes surrounded by thick disks of gas – are gargantuan structures that lie at the heart of galaxies between 0.3 and 11.4 billion light-years from Earth.
"We found the black holes serendipitously," explained David Alexander, a NuSTAR team member based in the Department of Physics at Durham University in England "We were looking at known targets and spotted the black holes in the background of the images."
The research team expects that there will be additional serendipitous finds such as these during the duration of the mission. The mission plan calls for targeted surveys of selected patches of sky, along with hundreds of random images that the team will comb through with the goal of finding black holes caught in the background.
The research team examined previous data from NASA’s Chandra X-ray Observatory and the European Space Agency's XMM-Newton satellite, two complementary space telescopes that see lower-energy X-ray light. They found the that 10 black holes had been detected before, however, it wasn’t until the NuSTAR observations that they stood out as exceptional and needing closer inspection.
The astronomers hope to solve the mysteries of black holes by combining observations taken across the range of the X-ray spectrum.
"We are getting closer to solving a mystery that began in 1962," said Alexander. "Back then, astronomers had noted a diffuse X-ray glow in the background of our sky but were unsure of its origin. Now, we know that distant supermassive black holes are sources of this light, but we need NuSTAR to help further detect and understand the black hole populations."
This X-ray glow is called cosmic X-ray background. It peaks at the high-energy frequencies that NuSTAR is designed to see, making the mission key to identifying what is producing the light, as well as finding the most hidden supermassive black holes buried behind their thick walls of gas.
"The highest-energy X-rays can pass right through even significant amounts of dust and gas surrounding the active supermassive black holes," said Fiona Harrison, the mission's principal investigator at the California Institute of Technology.
Missing pieces of the puzzle presented by black holes are also being provided by data from NASA's Wide-field Infrared Survey Explorer, or WISE, and Spitzer missions, which weigh the mass of the host galaxies.
"Our early results show that the more distant supermassive black holes are encased in bigger galaxies," said Daniel Stern, project scientist for NuSTAR at NASA's Jet Propulsion Laboratory. "This is to be expected. Back when the universe was younger, there was a lot more action with bigger galaxies colliding, merging and growing."
More information about the beastly happenings of black holes will be provided by future observations. NuSTAR is also searching for other exotic objects within the Milky Way as it hunts for remote black holes.
The details of this find have been published in the Astrophysical Journal.