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10 April 2014 11:44 am ,
Vol. 344 ,
The Pyrenean ibex, an impressive mountain goat that lived in the central Pyrenees in Spain, went extinct in 2000. But a...
Tight budgets are forcing NASA to consider turning off one or more planetary science projects that have completed their...
Ebola is not a stranger to West Africa—an outbreak in the 1990s killed chimpanzees and sickened one researcher. But the...
In an as-yet-unpublished report, an international panel of geoscientists has concluded that a pair of deadly...
Tropical disease experts tried and failed before to eradicate yaws, a rare disfiguring disease of poor countries. Now,...
Since 2002, researchers have reported that agricultural communities in the hot and humid Pacific Coast of Central...
Balkan endemic kidney disease surfaced in the 1950s and for decades defied attempts to finger the cause. It occurred...
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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.