Chorus of black holes radiates X-rays

From California Institute of Technology:


The blue dots in this field of galaxies, known as the COSMOS field, show galaxies that contain supermassive black holes emitting high-energy X-rays. They were detected by NASA’s Nuclear Spectroscopic… view more

Credit: NASA/JPL-Caltech

Supermassive black holes do not give off any of their own light, hence the word “black” in their name. However, many black holes pull in, or accrete, surrounding material, and emit powerful bursts of X-rays. Collectively, these active black holes throughout the sky can be thought of a cosmic choir, singing in the language of X-rays. Their “song” is what astronomers call the cosmic X-ray background.

To date, NASA’s Chandra mission has managed to pinpoint many of the individual black holes contributing to the X-ray background, but the ones that let out high-energy X-rays–those with the highest-pitched “voices”–have remained elusive.

New data from NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, has, for the first time, begun to pinpoint large numbers of the black holes sending out the high-energy X-rays. More technically, NuSTAR has made significant progress in resolving the high-energy X-ray background.

“We’ve gone from resolving just 2 percent of the high-energy X-ray background to 35 percent,” says Fiona Harrison, Benjamin M. Rosen Professor of Physics and Astronomy at Caltech, the principal investigator of NuSTAR, and lead author of a new study describing the findings in an upcoming issue of The Astrophysical Journal. “We can see the most obscured black holes, hidden in thick gas and dust.”

The results will ultimately help astronomers understand how the growth patterns of supermassive black holes change over time–a key factor in the development of black holes and the galaxies that host them. For instance, the supermassive black hole at the center of our Milky Way galaxy is dormant now, but …

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