The study reports that X7 is being pulled apart as the supermassive black hole, called Sagittarius A*, drags it closer. Credit: Anna Ciurlo/UCLA
Key points:
- Analyzing 20 years of data, scientists now believe X7 might be a cloud of dust and gas that came from the collision of two stars.
- Over the years, it has slowly been elongated as the black hole Sagittarius A* drags it closer to its center.
- The research team will continue to monitor X7’s dramatic changes as the black hole’s gravity pulls it apart.
For two decades, scientists have observed and speculated on the creation of an elongated object named X7 near the supermassive black hole close to the center of the Milky Way.
Examining 20 years of data gathered by the Galactic Center Orbit Initiative, astronomers from the UCLA Galactic Center Group and the Keck Observatory now believe X7 might be a cloud of dust and gas that came from the collision of two stars.
In the study published in The Astrophysical Journal, scientists report that over time X7 has stretched and it is being pulled apart as the black hole drags it closer to its center. X7 is expected to disintegrate within the next few decades, and the gas and dust its composed of will eventually be pulled closer to the black hole Sagittarius A*.
“No other object in this region has shown such an extreme evolution,” said Anna Ciurlo, a UCLA assistant researcher and the paper’s lead author. “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.”
X7 is 50 times the mass of Earth and on an orbital path around Sgr A* that would take 170 years to complete. But the team estimates that as X7 approaches Sgr A*, it's likely to just disappear.
Although X7’s origin is still the subject of debate, the finding suggests that it arose after two stars collided.
“One possibility is that X7’s gas and dust were ejected at the moment when two stars merged,” Ciurlo said. “In this process, the merged star is hidden inside a shell of dust and gas, which might fit the description of the G objects. And the ejected gas perhaps produced X7-like objects.”
The findings are the first estimate of X7’s mildly elliptical orbit and the most robust analysis to date of the changes to its appearance, shape and behavior. The research team will continue to monitor X7’s dramatic changes as the power of the black hole’s gravity yanks it apart.