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19 December 2013 12:36 pm ,
Vol. 342 ,
After 20 years of trying, researchers have finally convicted massive volcanic eruptions in Siberia as the culprit in...
Five federally funded optical and radio telescopes in the United States could be forced to shut down over the next 3...
A 2-year budget agreement pushes back the threat of sequestration but leaves scientists still wondering how much money...
After a decade away from physics, Robert Laughlin, a Nobel laureate at Stanford University in Palo Alto, California,...
Computer scientists and others have teamed up to persuade the 117 state parties to the Convention on Certain...
The swine flu pandemic of late 2009 had a peculiar aftereffect in parts of Europe: a spike in children being diagnosed...
- 19 December 2013 12:36 pm , Vol. 342 , #6165
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Video: Our Black Hole's Hidden Burps
25 October 2013 11:30 am
Video credit: NASA/CXC/A. Hobart
These days, the supermassive black hole at the center of our galaxy appears to be pretty docile. This wasn't always the case. New data from NASA's Chandra X-ray Observatory reveal that Sagittarius A* (Sgr A*, for short) once had spurts of high activity. To look at our local gravity trap's slightly more distant past, Chandra observed the x-ray light coming from gas clouds 30 light-years away from it. Fluorescence from these clouds is called a “light echo.” When a black hole sucks in matter, it produces x-ray waves. Like sound waves in a canyon, the x-ray light bounces off stuff that's nearby. The waves then make their way to Earth. Because the echoed light takes a detour on its way here, it offers information about Sgr A* that's older than the picture compiled from x-rays that travel directly from the black hole to us. Researchers compiled 12 years of Chandra's observations—shown above, with Sgr A* at right and the echoed x-ray emissions in blue—to find two major, distinct flare-ups of light echoes. They report this month in Astronomy & Astrophysics that signals from Sgr A* would have been, at times, 1 million times brighter than usual had we been observing it for the past couple hundred years. Further research will reveal what the increased activity levels say about Sgr A*'s eating habits—whether they are the last-gasps of a planet, a piece of a star, or maybe just some clumps of gas.