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6 March 2014 1:04 pm ,
Vol. 343 ,
Antiretroviral drugs can protect people from becoming infected by HIV. But so-called pre-exposure prophylaxis, or PrEP...
Two studies show that eating a diet low in protein and high in carbohydrates is linked to a longer, healthier life, and...
Considered an icon of conservation science, researchers at World Wildlife Fund (WWF) headquarters in Washington, D.C.,...
The new atlas, which shows the distribution of important trace metals and other substances, is the first product of...
Early in April, the first of a fleet of environmental monitoring satellites will lift off from Europe's spaceport in...
Since 2000, U.S. government health research agencies have spent almost $1 billion on an effort to churn out thousands...
Magdalena Koziol, a former postdoc at Yale University, was the victim of scientific sabotage. Now, she is suing the...
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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.