Mysterious object being dragged into black hole at Milky Way's centre: study

Stargazer Dave Cooke observes an unusual placement of the Milky Way, over a frozen fish sanctuary in central Ontario, north of Hwy 36 in Kawartha Lakes, Ont., on Sunday, March 21, 2021. (THE CANADIAN PRESS/Fred Thornhill)

A mysterious elongated object is being dragged into the supermassive black hole at the centre of our galaxy, according to a new study.

Led by astronomers from the UCLA Galactic Center Group and Keck Observatory in Hawaii, the study is based on two decades of observations of the object, which is known as X7. Researchers now believe it could be a cloud of gas and dust ejected when two stars collided.

"No other object in this region has shown such an extreme evolution,” UCLA assistant researcher and lead author Anna Ciurlo said in a news release. "It started off comet-shaped and people thought maybe it got that shape from stellar winds or jets of particles from the black hole. But as we followed it for 20 years we saw it becoming more elongated. Something must have put this cloud on its particular path with its particular orientation."

Researchers expect X7 to make its closest approach to the black hole known as Sagittarius A* around the year 2036. After that, they predict, X7 will disintegrate and spiral towards the black hole at the centre of the Milky Way before disappearing.

“We anticipate the strong tidal forces exerted by the galactic black hole will ultimately tear X7 apart before it completes even one orbit,” co-author and UCLA professor of physics and astronomy Mark Morris said.

The study was published this week in The Astrophysical Journal.

Although X7's origin is still uncertain, the merger of stars can be common near black holes.

"This is a very messy process: The stars circle each other, get closer, merge, and the new star is hidden within a cloud of dust and gas," Ciurlo explained. "X7 could be the dust and gas ejected from a merged star that’s still out there somewhere."

X7 has a mass of about 50 Earths and is moving towards the black hole at a speed of approximately 1,125 kilometres per second. The researchers plan to continue observing X7 as the power of the supermassive black hole's gravity eventually tears it apart.

"It's exciting to see significant changes of X7’s shape and dynamics in such great detail over a relatively short time scale as the gravitational forces of the supermassive black hole at the center of the Milky Way influences this object," co-author and Keck Observatory science operations lead Randy Campbell said. "It's a privilege to be able to study the extreme environment at the center of our galaxy."