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5 December 2013 11:26 am ,
Vol. 342 ,
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Second Black Hole for the Milky Way
11 November 2004 (All day)
Just half a light-year from the supermassive black hole in the center of the Milky Way, there may be another, much smaller black hole, embedded in a doomed cluster of stars. The discovery supports a popular scenario for the formation of medium-sized black holes, and it may explain the unexpected existence of young, massive stars in the core of the Milky Way.
There are two main types of black holes. Stellar black holes are the remains of exploded stars. They are just a few times heftier than the sun. On the other end of the scale are supermassive black holes, which lurk in the cores of galaxies and can weigh several billion times the mass of the sun. In recent years, astronomers using x-ray satellites have found evidence of medium-sized black holes, a few thousand times the sun's mass. They are thought to form in dense stellar clusters from chance collisions of massive stars.
One such stellar cluster, known as IRS 13E, lies close to the Milky Way's supermassive black hole. Jean-Pierre Maillard of the Astrophysical Institute in Paris and his colleagues studied IRS 13E using large telescopes at Mauna Kea, Hawaii, and in Chile. They discovered at least six bright stars that appear to be traveling through space together, suggesting that the stars are held together by the gravity of a massive central object. In a paper published in Astronomy & Astrophysics, Maillard and his colleagues estimate the mass of this putative black hole at 1300 times the mass of the sun.
According to theoretical astrophysicist Simon Portegies Zwart of the University of Amsterdam, the Netherlands, the find is "a fantastic confirmation" of a theory he and Steve McMillan of Drexel University in Philadelphia, Pennsylvania, put forward 2 years ago to explain the existence of young stars in the center of the Milky Way. These stars presented a puzzle because they are close to the central supermassive black hole, where the clouds of gas and dust needed to build stars would be disrupted by the hole's powerful tidal forces. However, based on computer simulations, Portegies Zwart and McMillan proposed that dense stellar clusters that formed farther out in a galaxy could spiral into the core and survive the pull of the supermassive black hole--if they were held together by a smaller black hole.
Richard Mushotzky of NASA's Goddard Space Flight Center in Greenbelt, Maryland, agrees that this is "potentially a fantastic result." However, he says, it would be much more clear-cut if IRS 13E was spewing x-rays, like the medium-sized black hole candidates in other galaxies.