A mysterious object slowly drifting toward the center of the Milky Way’s supermassive black hole could be the exploded remains of two colliding stars, a new study suggests.
Dubbed X7, the strange blob has a mass of about 50 Earths and is traveling at speeds of up to 1,125 km/h as it spirals into our galaxy central black holebeing pulled and stretched by powerful tidal forces as it falls.
Now, by analyzing 20 years of observational data, astrophysicists finally have a theory for what the blob is: a cloud of ejected debris created in a head-on collision between two merging stars. They published their findings on February 21 in The Astrophysical Journal (opens in new tab).
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“No other object in this region has shown such extreme evolution,” said the lead author Anna Ciurlo (opens in new tab)research associate at the University of California, Los Angeles, said in a statement (opens in new tab). “It started out as a comet, 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 getting longer. Something must have set this cloud on its special path with its special direction.”
black holes are born from the collapse of giant stars and grow by incessantly eating gas, dust, stars and other black holes in the star-forming galaxies they contain. This voracious feeding, combined with mergers with other black holes, can cause the cosmic monsters to expand to masses ranging from hundreds of thousands to billions of solar masses, turning them into the gargantuan supermassive black holes typically found in Earth centers of galaxies.
X7 is in a 170-year elliptical orbit around the Milky WayThe supermassive black hole of , dubbed Sagittarius A*. However, changes to the shape of the debris cloud suggest it won’t make it that far. Instead, it is torn apart by the massive black hole’s powerful gravity, expanding into a long, “spaghettified” noodle of matter before being swallowed up for good.
The researchers propose that X7 is a blob of gas and dust from the merger of two stars — an event they say is very common, particularly near black holes. As the stars collided and merged, they ejected a cloud of fiery plasma that later became a giant blob.
“It’s a very chaotic process: the stars orbit each other, get closer, merge, and the new star is hidden in a cloud of dust and gas,” Ciurlo said. “X7 could be the dust and gas being expelled from a merged star that’s still out there somewhere.”
To confirm their theory and observe the blob’s extreme changes towards the end of its life, astronomers will continue to examine the cloud for more clues.
“Continued monitoring of X7 will allow us to observe up close these extreme changes,” the researchers wrote in the paper, “which will result in the final tidal dispersal of the remains of this intriguing structure.”