‘Monster’ black holes spotted
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Two supermassive black holes were discovered behind clouds of gas and dust in two nearby galaxies.
Two supermassive black holes were discovered behind clouds of gas and dust in two nearby galaxies.
Scientists, using data from NASA telescopes, have spotted two supermassive black holes, located at the centres of galaxies close to our Milky Way, that were hidden behind clouds of gas and dust until now.
 
Monster black holes sometimes lurk behind gas and dust, hiding from the gaze of most telescopes. However, they give themselves away when material they feed on emits high-energy X-rays that NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) mission can detect.
 
Both black holes are the central engines of what astronomers call “active galactic nuclei,” a class of extremely bright objects that includes quasars and blazars.
 
“These black holes are relatively close to the Milky Way, but they have remained hidden from us until now,” said Ady Annuar, graduate student at Durham University in the U.K.
 
Depending on how these galactic nuclei are oriented and what sort of material surrounds them, they appear very different when examined with telescopes.
 
Active galactic nuclei are so bright because particles in the regions around the black hole get very hot and emit radiation across the full electromagnetic spectrum — from low-energy radio waves to high-energy X-rays. However, most active nuclei are believed to be surrounded by a doughnut-shaped region of thick gas and dust that obscures the central regions from certain lines of sight.
 
The active galactic nuclei that NuSTAR recently studied appear to be oriented such that astronomers view them edge-on. That means that instead of seeing the bright central regions, our telescopes primarily see the reflected X-rays from the doughnut-shaped obscuring material.
 
“Just as we can’t see the Sun on a cloudy day, we can’t directly see how bright these active galactic nuclei really are because of all of the gas and dust surrounding the central engine,” said Peter Boorman, graduate student at University of Southampton in the U.K, who led the study of an active galaxy called IC 3639, which is 170 million light years away.
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