A mysterious object in the center of the Milky Way was once believed to be a hydrogen gas cloud being sucked into our galaxy's massive black hole; new observations suggest the object is actually a pair of binary stars that had been orbiting the black hole in tandem and eventually merged into one.
The researchers determined the object, dubbed G2, was most likely not a gas cloud because it would be too easily ripped apart by the enormous black hole, UCLA reported.
"G2 survived and continued happily on its orbit; a simple gas cloud would not have done that," said study leader Andrea Ghez, professor of physics and astronomy in the UCLA College. "G2 was basically unaffected by the black hole. There were no fireworks."
G2 is believed to be just one of many undiscovered stars existing in the same neighborhood as supermassive black holes. The researchers suggest most of these objects start out as binary stars, but merge into one as a result of the black hole's powerful gravitational pull. Once these stars merge they expand for more than one million years before settling back down.
"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 mergers that are calm now," Ghez said.
G2 appears to be in its inflated stage and is now undergoing "spaghetti-fication," a phenomenon that occurs near black holes in which objects become elongated. The surface of the star is also being heated by neighboring stars, creating an enormous cloud of gas and dust.
"We are seeing phenomena about black holes that you can't watch anywhere else in the universe," Ghez said. "We are starting to understand the physics of black holes in a way that has never been possible before."
The findings were made with equipment from Hawaii's W.M. Keck Observatory, which houses the world's two largest optical and infrared telescopes. The study was published Nov. 3 in the journal Astrophysical Journal Letters.
