Keck Observatory NIRC2 and adaptive optics image taken in summer 2021 showing gas and dust structures at the galactic center, including objects G and X7. Credit: A. Ciurlo et al./UCLA GCOI/WM Keck Observatory

Two decades of monitoring from the WM Keck Observatory on Mauna Kea in Hawaii reveal that a peculiar cloud called X7 is breaking apart as it accelerates toward the supermassive black hole at the center of our Milky Way galaxy.

Astronomers at the UCLA Galactic Center Orbits Initiative (GCOI) and Keck Observatory have been tracking the evolution of this dusty filament of gas since 2002; High-angular-resolution near-infrared images captured with Keck Observatory’s powerful adaptive optics system show that X7 has become so elongated that it now has a length of 3,000 times the distance between Earth and the sun (or 3,000 astronomical units).

The study is published in today’s issue of The Astrophysical Journal.

“This is a unique opportunity to observe the effects of tidal forces on the black hole in high resolution, giving us insight into the physics of the extreme environment of the Galactic Center,” said Anna Ciurlo, UCLA research assistant and lead author. of the study.

Tidal forces are the gravitational pull that pulls an object as it approaches a black hole; the side of the object closest to the black hole is attracted much more strongly than the side that is farther away.

“It is exciting to see significant changes in the shape and dynamics of X7 in such detail on a relatively short timescale, as the gravitational forces of the supermassive black hole at the center of the Milky Way influence this object,” said co-author Randy Campbell, science operations leader at Keck Observatory.

X7 has a mass of about 50 Earths and is on an orbital path around our galaxy’s black hole, called Sagittarius A* (or Sgr A*), that would take 170 years to complete.

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

Based on its trajectory, the team estimates that X7 will get closest to Sgr A* around the year 2036 and then completely dissipate soon after. The gas and dust that make up X7 will eventually be sucked into Sgr A* and can then cause some fireworks as it heats up and spirals towards the black hole.

These findings are the first estimate of X7’s slightly eccentric orbital path and the most robust analysis to date of the remarkable changes in its appearance, shape, and behavior. To observe X7, the team used the Keck Observatory’s OH-suppressed infrared imaging spectrograph (OSIRIS) and second-generation near-infrared camera (NIRC2), in combination with the adaptive optics systems of the Keck I and Keck telescopes. II.

X7 has a mass of about 50 Earths and is on an orbital path around our galaxy’s black hole, called Sagittarius A* (or Sgr A*), that would take 170 years to complete.

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

Based on its trajectory, the team estimates that X7 will get closest to Sgr A* around the year 2036 and then completely dissipate soon after. The gas and dust that make up X7 will eventually be sucked into Sgr A* and can then cause some fireworks as it heats up and spirals towards the black hole.

These findings are the first estimate of X7’s slightly eccentric orbital path and the most robust analysis to date of the remarkable changes in its appearance, shape, and behavior. To observe X7, the team used the Keck Observatory’s OH-suppressed infrared imaging spectrograph (OSIRIS) and second-generation near-infrared camera (NIRC2), in combination with the adaptive optics systems of the Keck I and Keck telescopes.

Although X7’s origin remains a secret waiting to be unlocked and confirmed, the research team has some clues about its possible formation.

“One possibility is that gas and dust from X7 were ejected at the time the two stars merged,” Ciurlo said. “In this process, the merged star is hidden within a shell of dust and gas, which could fit the description of G objects. And the expelled gas may have produced X7-like objects.”

The research team will continue to monitor X7’s dramatic changes with the Keck Observatory as the power of the black hole’s gravity pulls it apart.

“It is a privilege to be able to study the extreme environment at the center of our galaxy,” Campbell said. “This study can only be done using Keck’s magnificent capabilities and done on revered Maunakea, with honor and respect for this special site.”