James Webb telescope confirms a supermassive black hole running away from its host galaxy at 2 million mph, researchers say
A shock wave, far away in space, could be the telltale sign of the first confirmation of a “runaway” supermassive black holeescaping from its host galaxy at 2.2 million miles per hour (3.6 million km/h).
The potential confirmation by the James Webb Space Telescope (JWST), published on the preprint server Arxiv on December 3, has not yet been peer-reviewed. But it was submitted to Astrophysical Journal Letters and to the study’s lead author. Pieter van Dokkumprofessor of astronomy and physics at Yale University, published several peer-reviewed articles on supermassive black hole candidates in recent years.
Trace a stream of stars
The candidate black hole was first spotted in 2023 by van Dokkum’s team, who saw a faint line in an archival image from the Hubble Space Telescope. The sight was so strange that the team made further observations from the Keck Observatory in Hawaii.
Observations at the time showed that the black hole had a mass of 20 million suns and that the strange line was a “wake” of young stars spanning 200,000 light years space – twice the diameter of the entire Milky Way. The Hubble image captures a time when the universe was about half its current age of 13.8 billion years.
“We suspected that this strange object might be a runaway supermassive black hole, but we didn’t have compelling proof,” van Dokkum said. So for their new research, the team turned to JWST, a deep space observatory unique in its “sensitivity and sharpness,” van Dokkum said, “to see the bow shock created by the speed of the black hole.”
The resulting images stunned the team.
JWST’s mid-infrared instrument rendered the shock wave, or arc shock, at the leading edge of the candidate black hole with unprecedented clarity. “It’s a bit like the waves created by a ship,” van Dokkum said. “In this case the ship is a black hole and very difficult to see, but we can see the ‘water’ – actually hydrogen and oxygen gas – which [the black hole] pushes before him.”
Van Dokkum was surprised. “Everything about this object told us that this was something really special, but seeing this clear signature in the data was incredibly satisfying,” he added.
In addition to JWST’s resolution, van Dokkum said his study showed that the observations matched data from Hubble and Keck in different wavelengths of light. The data “all provide different pieces of the puzzle,” he said, “and they fit together beautifully – exactly as the theoretical models predict.”
A supermassive mystery
Studying runaway black holes, like this one, shows scientists more about how galaxies and black holes evolved, van Dokkum said. Most large galaxies have supermassive black holes embedded in their centers, including our own Milky Way. Their ability to escape their close galactic bonds remains a long-standing mystery.
According to van Dokkum, the only way for a supermassive black hole to be ripped out of its galaxy is if at least two such black holes come extraordinarily close to each other, with the intense gravitational interaction “pushing one of them out.”
The new research suggests that the candidate runaway was produced after at least two, and potentially up to three, black holes all interacted. With masses of at least 10 million suns each, van Dokkum said the violence of the encounter must have been “quite something.”
As for where to look next for a runaway supermassive black hole, the research paper notes “several promising candidates,” but interpreting these systems is difficult. An example is the ambiguous object known as the “Cosmic Owl”, which is approximately 11 billion light years from Earth.
The Cosmic Owl, according to the new paper, includes two galactic cores – each with an active supermassive black hole at the galaxy’s heart – and a third supermassive black hole that is, curiously, “embedded in a gas cloud” between the two galaxies.
How this third black hole arrived in a gas cloud is a matter of controversy. Some researchers say the black hole could be a fugitive that escaped from one of the host galaxies, but JWST observations by van Dokkum’s group challenge this interpretation. Their observations suggest that it is a displaced black hole “more likely…formed in situ by a direct collapse” of gas, produced by shock waves after the two galaxies nearly collided.
Further study is needed on this and other objects that may contain possible black hole fugitives. Van Dokkum cited the current Euclid and to come Nancy Grace Romain Space telescopes are promising survey instruments because these telescopes are designed to observe the entire sky, unlike the JWST. “This will tell us how often this happens – something we would very much like to know.”
