August 13, 2014
Rare Event Captured In Region Around A Supermassive Black Hole
April Flowers for redOrbit.com - Your Universe Online
An extreme and rare event in the region of space immediately surrounding a supermassive black hole has been captured by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR. The corona of the black hole, a compact source of X-rays that is situated nearby, has moved closer to the black hole over a period of just days.
"The corona recently collapsed in toward the black hole, with the result that the black hole's intense gravity pulled all the light down onto its surrounding disk, where material is spiraling inward," said Michael Parker of the Institute of Astronomy in Cambridge, UK. The findings are described in a recent issue of the Monthly Notices of the Royal Astronomical Society.
The gravity of the black hole exerts even more of a pull on the X-rays emitted by the corona as it shifts closer, causing an extreme blurring and stretching of the X-ray light. Scientists have observed such events before, but never in such detail and to such a degree.
Astronomers believe that supermassive black holes are at the center of all galaxies, though some are more massive and rotate faster than others. Markarian 335 (Mrk 335), the black hole in this study, is approximately 324 million light-years from Earth towards the Pegasus constellation. Mrk 335 is one of the most extreme systems for which scientists have measured the mass and the spin rate — the black hole is 10 million times the mass of our sun, and spins so rapidly that space and time are dragged around with it.
Some light falls into a black hole, never to be seen again. Other high-energy light, however, emanates from both the corona and the surrounding accretion disk of superheated material. The shape and temperature of coronas is uncertain, however, it is known that they contain particles moving at near the speed of light.
Mrk 335 has been monitored by NASA's Swift satellite for years. The Swift team recently noted a change in the X-ray brightness of the black hole. NuSTAR, in what is called a target-of-opportunity observation, was redirected to examine the high-energy X-rays (in the 3 to 79 kiloelectron volts range) being emitted from this source. In this energy range of X-rays, astronomers are able to gain a detailed look at the event horizon — that region around a black hole from which light can no longer escape gravity.
Months after the first movement was detected, follow-up observations indicate the corona is still in this close configuration to the black hole. It is uncertain whether or not the corona will shift back to its original position, and if so, when. NuSTAR observations have also revealed that the inner portion of the black holes superheated disk is being illuminated by light pulled from the corona by the black holes gravity.
The data gained from this study could, ultimately, help astronomers understand a great deal more about the nature of black hole coronas. The data has also allowed the scientists to obtain better measurements of Mrk 335's furious relativistic spin rate—relativistic speeds approach the speed of light, as Albert Einstein's theory of relativity describes.
"We still don't understand exactly how the corona is produced or why it changes its shape, but we see it lighting up material around the black hole, enabling us to study the regions so close in that effects described by Einstein's theory of general relativity become prominent," said NuSTAR Principal Investigator Fiona Harrison of the California Institute of Technology (Caltech). "NuSTAR's unprecedented capability for observing this and similar events allows us to study the most extreme light-bending effects of general relativity."
Image 2 (below): This plot of data captured by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, shows X-ray light streaming from regions near a supermassive black hole known as Markarian 335. Credit: NASA/JPL-Caltech/Institute for Astronomy, Cambridge
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