!A mysterious object dragged into the black hole at the center of our galaxy
For decades, astronomers have watched a mysterious blob called X7 drift around the supermassive black hole at the heart of the Milky Way, wondering where it came from.
By analyzing 20 years of observations, a team of scientists led by UCLA astrophysicist Anna Ciorlo discovered a dramatic shift in the shape of X7, as it expanded to almost twice its initial length.
This change in structure indicates that the strange blob is likely made of debris ejected during a relatively recent collision between two stars.
"No other body in this region has shown such extreme evolution," Cirlu explains. It started out as a comet and people thought it might have gotten that shape from stellar winds or jets of particles from the black hole. But as we've followed them for 20 years, we've seen them become more elongated. Something must have put this cloud on its surface. A path of its own direction.
And if the debris cloud is indeed the object, its discovery sheds light on some fascinating dynamics at the center of the galaxy, such as the frequency of stellar collisions and the intense gravitational effects. In just a few short years, the cloud of dust and gas will become more and more complex and will fall into the black hole (SgrA*).
By studying X7 over a period of years, researchers were able to calculate its mass, which weighs about 50 times that of Earth.
Changes in the debris cloud's position and velocity also indicate that it is in an elliptical orbit around the center of the galaxy, with a period of about 170 years. Or rather, it would be so, if they were together a little more. Simulations indicate that it will not have the opportunity to complete one orbit.
Its closest approach to Sgr A*, known as a periastron, is expected to occur in 2036. At that point, the gravitational environment will tear the cloud apart, leaving the scattered remnants to continue orbiting the black hole until it irreversibly disappears beyond event horizon.
"It's exciting to see significant changes in the shape and dynamics of X7 in great detail over a relatively short period of time, as the gravitational forces of the supermassive black hole at the center of the Milky Way galaxy act on this object," said co-author astronomer Randy Campbell of the Keck Observatory.
X7 shares some similarities with other mysterious blobs orbiting the center of the galaxy, known as G Objects. They were first discovered about 20 years ago, and posed an important mystery: they looked like clouds of gas, but behaved like stars, stretching out at perihelion, only to emerge intact and shrink back into a more compact shape to continue their orbits.
Astronomers hypothesized that the G objects were stars merging together, producing a huge cloud of material that remained within the gravitational field of the newly merged star, hiding it from view. Then a study published in 2021 found that one such object, G2, was a molecular cloud, hiding three small stars.
And while there are similarities, the X7 is significantly different from the G Objects, too. Its evolution was more dramatic than that of G bodies, both in shape and in speed as it expanded and accelerated towards Sgr A*.
"One possibility is that X7 gas and dust were emitted at the moment two stars merged," says Cirlu. In the process, the merged star is hidden within a shell of dust and gas, which may fit the description of G objects.”
Because X7 is not held together by an underlying mass at its center, it is expected to have a much shorter lifetime than that of G objects. Meanwhile, the compact star from which X7 bulged out could still be present at the center of the galaxy, in its own separate orbit. The researchers note that its orbit is very similar to that of object G G3, and they suggest that G3 may be the parent object.
However, it is not currently easy to rule out other possibilities. The X7 could be a piece of debris stripped from a larger cloud, for example.
And of course, watching the X7 should be fun and rewarding in itself, as it draws ever closer to its doom.
"Continued monitoring of X7 will allow us to closely view these extreme changes, ending with the tidal dissipation of the remnants of this intriguing structure," the researchers wrote.
Source : websites