HEAPOW: Accelerating Jellyfish (2013 Mar 04)
Black holes are strange regions of incredibly high density, where intense gravity warps spacetime to such an extent that nothing, not even light, can escape (unless, sneakily, through an Einstein-Rosen Wormhole). Black holes can rotate, and spinning black holes are even stranger than their non-spinning cousins: near a spinning black hole, both space and time rotate along with the black hole as well. Astronomers have tried to measure this distortion in a number of ways. One technique relies on measuring the distortion in X-ray emission of unfortunate iron atoms close to the black hole's event horizon. However, astronomers could not be certain that the observed distortions were produced by the effects of the spin of the black hole, or by mundane absorption due to cool material near the black hole. However, at least in one particularly important case, scientists have now been able to resolve this issue once and for all, thanks to the NuSTAR satellite. NuSTAR, and XMM-Newton, made observations of a two million solar mass black hole living in the center of a galaxy called NGC 1365, shown in the artist's conception above. The XMM-Newton observations clearly showed the distorted iron emission; but the NuSTAR observation also clearly showed emission of X-rays reflected from material in the black hole's inner accretion disk as well, allowing the effects of the black hole's spin to be clearly distinguished from the effects of absorption, providing a firm measure of the black hole's spin.
NuSTAR Helps Solve Riddle of Black Hole Spin
http://asterisk.apod.com/viewtopic.php?p=194109#p194109
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