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Adapted from a UCLA press release, November 3, 2014.

For years, astronomers have been puzzled by a bizarre object in the center of the Milky Way that was believed to be a hydrogen gas cloud headed toward our galaxy’s enormous black hole. (See Section 15.5, Chapter opener figure, p. 382, and Figure 15-5, p. 388.)

Having studied it during its closest approach to the black hole this summer, UCLA astronomers believe that they have solved the riddle of the object widely known as G2.

A team led by Andrea Ghez determined that G2 is most likely a pair of binary stars that had been orbiting the black hole in tandem and merged together into an extremely large star, cloaked in gas and dust – its movements choreographed by the black hole’s powerful gravitational field. The research is published today in the journal Astrophysical Journal Letters.

Astronomers had figured that if G2 had been a hydrogen cloud, it could have been torn apart by the black hole, and that the resulting celestial fireworks would have dramatically changed the state of the black hole. However, G2 survived and continues on its orbit unaffected.

G2 appears to be just one of an emerging class of stars near the black hole that are created because the black hole’s powerful gravity drives binary stars to merge into one. In our galaxy, massive stars primarily come in pairs. The star suffered an abrasion to its outer layer but otherwise will be fine.

Keck Observatory

Credit and copyright: Ethan Tweedie Photography

The team utilized the Keck Observatory’s adaptive optics technology, a powerful technology that corrects the distorting effects of the Earth’s atmosphere in real time to more clearly reveal the space around the supermassive black hole.

Links: full UCLA press release, Keck press release.

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