The Milky Way’s Supermassive Black Hole Has More Mysterious Objects Around It

The star cluster surrounding the Milky Way's supermassive black hole. NASA, ESA, and Hubble Heritage Team (STScI/AURA, Acknowledgment: T. Do, A.Ghez (UCLA), V. Bajaj (STScI)

The galactic center is an intriguing place. The supermassive black hole keeps things interesting with its huge gravitational pull, and astronomers are only now discovering just how many things they haven’t seen there. To add to the collection, researchers have announced the discovery of several peculiar objects.

Using the powerful Keck Observatory in Hawaii, researchers have discovered several dusty stellar objects that are difficult to classify. They look like big clouds of gas and dust but behave like stars. The team used 12 years' worth of data to complete this study, which was presented at the 232nd meeting of the American Astronomical Society in Denver.

“We started this project thinking that if we looked carefully at the complicated structure of gas and dust near the supermassive black hole, we might detect some subtle changes to the shape and velocity,” Randy Campbell, science operations lead at Keck Observatory, said in a statement. “It was quite surprising to detect several objects that have very distinct movement and characteristics that place them in the G-object class, or dusty stellar objects.”

The first two dusty stellar objects are called G1 and G2, and they were discovered in 2004 and 2012 respectively. Three more objects have now been added called G3, G4, and G5. At first, astronomers believed that G1 and G2 were gas clouds, but then they passed their closest approach to the supermassive black hole unscathed.

“If they were gas clouds, G1 and G2 would not have been able to stay intact,” co-principal investigator Professor Mark Morris of UCLA added. “Our view of the G-objects is that they are bloated stars – stars that have become so large that the tidal forces exerted by the central black hole can pull matter off of their stellar atmospheres when the stars get close enough, but have a stellar core with enough mass to remain intact. The question is then, why are they so large?”

The team thinks that these objects were formed by the merger of two stars. Over time, the gravity of the supermassive black hole would affect the orbit of binary stars until they collide. The end object would have an excess energy just like people see in these dusty stellar objects.

“In the aftermath of such a merger, the resulting single object would be 'puffed up', or distended, for a rather long period of time, perhaps a million years, before it settles down and appears like a normal-sized star,” said Morris.

It has been an exciting year for the core of the Milky Way. A few months ago, researchers discovered a dozen small black holes, hinting at thousands more hiding.

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