Twenty years of monitoring with the Keck Telescope on Maunakea in Hawaii revealed that the strange stellium was stretched as it accelerated toward the supermassive black hole at the center of the Milky Way.
Since 2002, astronomers at UCLA’s Galactic Center Orbits Initiative (GCOI) and the Keck Telescope have been tracking the evolution of the nebula known as X7; High-resolution near-infrared images show that X7 has become elongated and is now 3,000 times (or 3,000 AU) the distance from Earth to the sun. The research was published in The Astrophysical Journal.
“This is a unique opportunity to observe the effects of black hole tidal forces at high resolution, giving us insight into the physics of the extreme environment at the center of our galaxy,” said lead author Anna Ciurlo, a UCLA research associate and lead author. Tidal forces are the gravitational pull that stretches objects close to a black hole. The side of the object closest to the black hole is pulled much more than the farthest side, so the object is stretched.
“As the gravity of the supermassive black hole at the center of the Milky Way affects this object, it’s exciting to see dramatic changes in X7’s shape and dynamics in a relatively short period of time,” said co-author Randy Campbell, head of science operations at the Keck Telescope.
X7 has a mass of about 50 Earths, and is located around the black hole Sagittarius A* (or Sgr A*) in the center of the Milky Way, with an orbital period of 170 years.
Co-author Mark Morris, a professor of physics and astronomy at UCLA, predicts that the powerful tidal forces of the black hole at the center of the galaxy will eventually tear X7 apart before it completes one orbit.
According to the trajectory of X7, the team estimates that X7 will be closest to Sagittarius A* around 2036, and then dissipate soon. The gas and dust that make up X7 will eventually be dragged toward Sagittarius A*, where it may then spark as it heats up and spirals into the black hole.
Check out this animation by @AdamGDog showing X7’s anticipated fate as it makes its closest approach to Sgr A* around the year 2036, giving insight into the extreme environment of the Galactic Center. Congrats to Anna Ciurlo of @GalacticCtrGrpRandy, & the entire team! pic.twitter.com/zdyjIPoUGA
— W. M. Keck Observatory (@keckobservatory) February 21, 2023
These findings represent the first estimate of the X7’s mildly elliptical orbital path, and the most reliable analysis to date of significant changes in appearance, shape and behavior. In order to observe X7, the team used the OH-Suppressing Infrared Imaging Spectrograph (OSIRIS) and the second-generation near-infrared camera (Near-Infrared Camera, NIRC2) of the Keck Observatory, as well as the Keck I and Keck II telescopes. Adaptive optics system.
X7 displays the same properties as other strange dusty objects orbiting Sgr A* called G objects, which look like gas but behave like stars. However, compared with the G celestial body, the shape and velocity structure of X7 have greater changes. The stretched filaments of gas and dust move rapidly, at about 90 miles per second. Due to the huge mass of the black hole, all nearby celestial bodies move much faster than the rest of the Milky Way.
While the origin of the X7 remains a mystery to be solved and confirmed, the team has some possible clues about its formation.
Ciurlo said: One of the possibilities is that the gas and dust of X7 are ejected when two stars merge, and the merging star is hidden in the dust and gas shell during the process, which may be consistent with the cause of the G celestial body. The ejected gas could have produced an X7-like object. The research team will continue to work with the Keck telescope to monitor X7’s dramatic changes in the black hole’s tidal forces.
▲ Keck Observatory NIRC2 and adaptive optics system images taken in summer 2021, showing the structure of gas and dust in the center of the Milky Way, including G objects and X7. (Source: WM Keck Observatory, the same below)
▲ Images taken using the Keck Observatory NIRC2 and adaptive optics system, showing the evolution of the X7 from 2002 to 2021.
(This article is reproduced with the authorization of Taipei Planetarium; the source of the first picture:Filmscreenshot)
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