Mysterious object at hart of our galaxy
- November 07, 2014
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Astronomers say they have solved a mystery about a thin, bizarre object headed toward the monster black hole at the center of our galaxy.
The scientists studied the object, known as G2, during its closest approach to the black hole this summer, and found the black hole didn't eat it. Black holes are objects so compact that nothing can escape their gravitational pull, not even light. They can't be seen directly, but their characteristic influence on nearby objects can.
While some scientists believed G2 was a cloud of hydrogen gas that the black hole would tear apart in a fiery show, the researchers in the new study found it was more interesting.
“G2 survived and continues happily on its orbit; a gas cloud would not do that,” said Andrea Ghez, University of California Los Angeles astronomer who directs the university's Galactic Center Group. It “was completely unaffected by the black hole; no fireworks.”
Instead, the team found it was a pair of binary stars, or stars that circle each other. The pair had also been orbiting the black hole together, they said, and merged together into an extremely large star, cloaked in gas and dust. The black hole's powerful gravitational field choreographed the event.
“G2 is not alone,” said Ghez, who uses W. M. Keck Observatory in Hawaii to study thousands of stars in the neighborhood of the so-called supermassive black hole. “We're seeing a new class of stars near the black hole, and as a consequence of the black hole.”
The observatory uses a technology called adaptive optics to correct the distorting effects of the Earth's atmosphere in real time and see more clearly.
“We are seeing phenomena about black holes that you can't watch anywhere else in the universe,” Ghez added. “We are starting to understand the physics of black holes in a way that has never been possible before, and is possible only at the center of the galaxy,” where the supermassive black hole lurks.
Massive stars in our galaxy, she added, mainly come in pairs. When the two merge into one, the star expands for more than one million years “before it settles back down,” Ghez said. “This may be happening more than we thought; the stars at the center of the galaxy are massive and mostly binaries. It's possible that many of the stars we've been watching and not understanding may be the end product of a merger that are calm now.”
G2, in that explosive stage now, has been an object of fascination. “Its closest approach to the black hole was one of the most watched events in astronomy in my career,” Ghez said.
G2 makes an unusual, 300-year elliptical orbit around the black hole and Ghez's group calculated its closest approach occurred this summer-later than other astronomers believed. The research was published Nov. 3 in the journal Astrophysical Journal Letters.
source : www.world-science.net