Bizarre cloud near our black hole identified

 A new class of star may be being formed at the centre of our Galaxy

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The Keck Observatory's infrared cameras reveal the cloud survived its journey past our central black hole, circled in green.

Credit: Andrea Ghez, Gunther Witzel/UCLA Galactic Center Group/W. M. Keck Observatory


For years, a strange object has been making its way towards the centre of the Milky Way. At first astronomers believed that the object, named G2, was a cloud of hydrogen gas about to be consumed by our Galaxy’s black hole.

But observations recently taken with the W. M. Keck telescope have revealed that it is actually a new class of star: a pair of binary stars that have merged together under the intense gravity of the black hole.

“G2 is not alone,” said Ghez, who uses Keck Observatory to study thousands of stars in the neighbourhood of our supermassive black hole. “We’re seeing a new class of stars near the black hole, and as a consequence of the black hole.”

Ghez and her team were investigating these stars as a way of studying our nearest supermassive black hole. They discovered that there were many young stars where none were expected and that there was a distinct lack of older generations of stars.

It now appears that a new class of star, of which G2 is one, is responsible. Most of the massive stars in the Galaxy exist in binary pairs and the same is true near the Milky Way’s black hole. However, the intense gravity near the black hole forces these pairs to merge into one massive star. For more than a million years the star expands, cloaking itself in gas and dust creating its nebulous appearance, then settling back down into a large, youthful looking, star.

“This may be happening more than we thought; the stars at the centre of the Galaxy are massive and mostly binaries,” says Ghez. “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.”

 

Carouselle credit: Ethan Tweedie Photography


 

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