(ORDO NEWS) — For decades, astronomers have watched a mysterious orb called X7 drift around the supermassive black hole at the center of the Milky Way, trying to figure out where it came from.
After analyzing observations over 20 years, a team of scientists led by UCLA astrophysicist Anna Siurlo found a sharp change in the shape of X7, which almost doubled its original length.
This change in structure suggests that the strange blob is most likely created by debris ejected during a relatively recent collision between two stars.
“No other object in this region has shown such extreme evolution,” Siurlo explains.
“It started as a comet… and people thought maybe it got that shape because of stellar winds or jets of particles from a black hole.
But as we have followed it for 20 years, we have seen it become more and more elongated. Something must have directed this cloud to a specific path with a specific orientation.”
If the debris cloud is indeed such an object, its discovery sheds light on some surprising phenomena at the galactic center, such as the frequency of stellar collisions and the effects of extreme gravity.
In just a few short years, the cloud of dust and gas will become more and more spaghetti and fall into the black hole Sagittarius A* (SgrA*.).
By studying X7 for several years, the researchers were able to calculate its mass, which is about 50 times the mass of the Earth.
This may be a lot for an inhabitant of the Earth, but in space it is practically a sneeze, not even equating to a sixth of the mass of Jupiter.
Changes in the position of the debris cloud and its speed also suggest that it is in an elliptical orbit around the galactic center with a period of about 170 years.
Rather, it would be if there were a little more together. The simulation assumes that it will not have the opportunity to complete one orbit.
Its closest approach to Sagittarius A*, known as periastron, is predicted to occur in 2036.
At this point, the gravitational environment will tear the cloud apart, leaving scattered remnants that will continue to circle around the black hole until they irrevocably disappear beyond its event horizon.
When this finally happens, any observer can see the fireworks.
“It’s great to see the X7’s massive shape and dynamics changes in such minute detail in a relatively short amount of time.
The gravitational forces of the supermassive black hole at the center of the Milky Way affect this object,” says astronomer and co-author Randy Campbell of the Keck Observatory.
X7 bears some resemblance to other mysterious blobs orbiting around. galactic center known as G-objects.
First discovered about 20 years ago, they were a major mystery: they looked like gas clouds but behaved like stars, stretching out into the periastron but appearing whole and shrinking into a more compact shape to continue their orbit.
Astronomers hypothesized that G-objects were stars that merged together, creating a huge cloud of material that remained in the gravitational field of the newly merged star, hiding it from view.
Then a study published in 2021 showed that one of these objects, G2, is a molecular cloud hiding three newborn stars; but the identities of the rest remain unknown.
Despite the similarities, X7 also differs significantly from G objects. Its evolution has been more dramatic than that of G objects, both in shape and speed, as it stretches and accelerates in the direction of Sgr A*.
Thus, X7 may not belong to the same object type as G-objects. but it might be related.
“One possibility is that the gas and dust of X7 were ejected at the time of the merger of two stars,” Chiurlo says.
“In this process, the merged star is hidden inside a shell of dust and gas, which may fit the description of G objects. And the ejected gas may have produced objects like X7.”
Because X7 is not expected to be held together by the mass lurking at its center and will have a much shorter lifespan than G objects; this may be why other members of this species have not yet been discovered.
Meanwhile, the merged star from which X7 puffed might still be somewhere out there, at the galactic center, in its own separate orbit.
The researchers note that its orbit is very similar to that of the G3 object and speculate that G3 could be the parent object.
However, it is currently not easy to rule out other possibilities. For example, X7 could be a piece of garbage separated from a larger cloud. Further observations may help narrow it down.
And of course, watching the X7 should be interesting and rewarding in its own right as it moves closer and closer to its doom.
“Continuous observation of X7 will allow us to closely observe these extreme changes,” the researchers write, “ending in the final dissipation of the remnants of this intriguing structure by tides.”
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