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17 April 2014 12:48 pm ,
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Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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The Runaway Star
10 February 2005 (All day)
Astronomers have discovered a star traveling so fast that even the gravity of the entire Milky Way can't stop it. Theoretical calculations suggest that thousands of these runaway stars may be racing through our galaxy, providing further evidence that a supermassive black hole lurks in the core of the Milky Way.
The main idea, first posited in 1988, is that two stars orbiting each other can be disrupted when they pass close to a massive black hole in the core of a galaxy. One star ends up orbiting the black hole, while the other is ejected like a stone from a sling. In our own Milky Way, this is expected to happen once every 100,000 years or so. A team of astronomers from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, led by Warren Brown, has now identified one such stellar outcast.
The faint star is some 180,000 light years away in the constellation Hydra the Water Snake. Using the 6.5-meter telescope of the MMT Observatory at Mount Hopkins, Arizona, the team clocked the star at over 700 kilometers per second, almost 25 times the orbital velocity of Earth, and more than twice the so-called escape velocity of the Milky Way galaxy. Based on its position, velocity, and direction of motion, the team concludes that the star must have been ejected by the central black hole some 80 million years ago. Nothing else could crank up the velocity so high, they conclude in an upcoming issue of Astrophysical Journal Letters.
"It's a pretty interesting discovery," says Andrea Ghez of the University of California at Los Angeles. She believes the findings could also explain why so many young and massive stars are found in tight orbits around the Milky Way's black hole, where astronomers normally wouldn't expect them to be.