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10 April 2014 11:44 am ,
Vol. 344 ,
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...
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In an as-yet-unpublished report, an international panel of geoscientists has concluded that a pair of deadly...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,...
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ScienceShot: 'Quiet' Black Holes May Be Lurking Throughout Galaxy
15 January 2014 1:15 pm
Although black holes emit no light, all those that are several times more massive than the sun came to attention because hot gas falling into them gives off x-rays. That's how astronomers found the first black hole, Cygnus X-1; no less an authority than the rock band Rush declared that "the x-ray is her siren song." Now, for the first time, astronomers have managed to discover a stellar-mass black hole without using x-ray observations. Located 8500 light-years from Earth, the dark object orbits a bright, blue star named MWC 656 that spins so fast it flings gas (colored red in this artist's conception) around itself; additional gas (colored blue) swirls around the black hole but doesn't fall in, explaining the lack of x-rays. By measuring Doppler shifts of the two gaseous disks as they orbit each other every 60.37 days, the scientists deduce that the dark object weighs 3.8 to 6.9 times more than the sun—massive enough to be a black hole, the researchers report online today in Nature. The discovery suggests that many other equally quiescent black holes inhabit the galaxy, unknown to astronomers.