Using new data from NASA’s Chandra X-ray Observatory and Neil Gehrel’s Swift Observatory, as well as ESA’s XMM-Newton, a team of researchers has made important advances in understanding how and when a supermassive black hole accretes and then consumes material, as described in our recent press release.
This artist’s impression shows a star partially destroyed by such a black hole in the AT2018fyk system. The supermassive black hole in AT2018fyk – with about 50 million times more mass than the Sun – is located at the center of a galaxy about 860 million light-years from Earth.
Astronomers have found that a star in AT2018fyk is on a highly elliptical orbit around the black hole, so its closest point to the black hole is much larger than its closest point. During its closest approach, the black hole’s tidal forces pull some material away from the star, creating two tidal tails of “star debris.”
The image shows a point in the orbit shortly after the star has been partially destroyed, when the tidal tails are still very close to the star. Later in the star’s orbit, the destroyed material returns to the black hole and loses energy, causing a large increase in X-ray brightness that occurs later in the orbit (not shown here). This process repeats each time the star returns to its point of closest approach, which occurs approximately every 3.5 years. The image shows the star during its second orbit and the disk of X-ray emitting gas around the black hole that forms as a byproduct of the first tidal encounter.
Researchers became aware of AT2018fyk in 2018 when the ASAS-SN ground-based optical survey found that the system had become much brighter. After observing with NASA’s NICER and Chandra, as well as XMM-Newton, researchers determined that the increase in brightness came from a “tidal disruption event” (TDE), which indicates that a star was completely ripped apart and partially swallowed after passing too close to a black hole. Chandra data from AT2018fyk are shown in the inset of a larger field-of-view optical image.
As material from the destroyed star approached the black hole, it became hotter and produced X-ray and ultraviolet (UV) light. These signals then faded, consistent with the theory that there was nothing left of the star for the black hole to process.
About two years later, however, the galaxy’s X-ray and UV light became significantly brighter again. This meant, astronomers said, that the star had likely survived the black hole’s initial gravitational grip and then entered a highly elliptical orbit with the black hole. On its second approach to the black hole, more material was ripped off, producing more X-ray and UV light.
Based on what they learned about the star and its orbit, a team of astronomers predicted that the black hole’s second meal would end in August 2023 and requested Chandra observation time to verify this. Chandra observations on August 14, 2023, did indeed show the telltale sign that the black hole’s feeding was coming to an end with a sudden drop in X-rays. The researchers also got a better estimate of how long it takes the star to complete a full orbit and predicted future meals for the black hole.
A paper describing these results appears in the August 14, 2024 issue of the Astrophysical Journal and is available online. The authors are Dheeraj Passam (Massachusetts Institute of Technology), Eric Coughlin (Syracuse University), Muryel Guolo (Johns Hopkins University), Thomas Wevers (Space Telescope Science Institute), Chris Nixon (University of Leeds, UK), Jason Hinkle (University of Hawaii at Manoa) and Ananaya Bandopadhyay (Syracuse).
NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center manages scientific investigations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
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In this digital illustration, a star sheds stellar debris as it orbits a supermassive black hole. This artist’s impression depicts the center of a galaxy about 860 million light-years from Earth.
The supermassive black hole is at the top left. It resembles an irregular, jet-black sphere at the center of an almond-shaped pocket of swirling sand and dirt. Although the swirling brown-gray pocket has a grainy texture, it is actually a disk of hot gas.
The orbiting star can be seen at the bottom right. In this image, the star is relatively close to us, with the black hole far behind it. The star is a blue-white sphere that appears slightly larger from this perspective than the distant black hole.
Two tapered streaks break away from the bright star like the pulled-back corners of a smile. These streaks represent tidal tails of stellar debris; material pulled from the star’s surface by the black hole’s gravity. This partial destruction of the star occurs every 3.5 years, when the star’s orbit brings it closest to the supermassive black hole.
As it orbits, the black hole digests stellar debris from its tidal tails. A byproduct of this digestion is X-ray gas, which swirls in a disk around the black hole.
At the top left of the grid is an image of the distant galaxy cluster MACS J0416. Here, the blackness of space is full of glowing dots and tiny shapes in shades of white, purple, orange, gold, and red, each a galaxy in its own right. Close inspection (and a lot of zoom!) reveals the spiral arms of some of the seemingly tiny galaxies in this highly detailed image. A soft purple band runs gently down the center of the frame; a reservoir of superheated gas discovered by Chandra.
Megan Watzke
Chandra X-ray Center
Cambridge, Massachusetts.
617-496-7998
Lane Figueroa
Marshall Space Center
Huntsville, Alabama.
256-544-0034
