A runaway black hole fleeing a distant galaxy has been spotted

A streak of light extending from a distant galaxy may be First sure sign of a supermassive black hole escaping, reports a new study. A putative black hole fleeing its host galaxy appears to leave a trail of newborn stars and gas in its wake. If confirmed, space escapees could help astronomers learn more about what happens to black holes when galaxies collide.

“It’s a very cool, serendipitous discovery,” says astronomer Charlotte Angus of the University of Copenhagen, who was not involved in the new work. “The possibility that this could be caused by a supermassive black hole that has been ejected from its galaxy is very exciting. These events have been predicted theoretically, but until now, there has been little evidence for them.” met.”

looking for collision of dwarf galaxies With the Hubble Space Telescope, astronomer Pieter van Dokkum and his colleagues observed something peculiar: a long, straight line that seemed to move away from a distant galaxy, becoming narrower and brighter as it became (Sn: 5/18/22,

“Whatever it is, we haven’t seen it before,” says Van Dokkum of Yale University. “Most celestial objects are spiral or blob-shaped. There aren’t many objects that are just a line in the sky.” When astronomers see lines, they are usually from something moving, such as a satellite crossing the telescope’s field of view ,Sn: 3/3/23,

To find out what it was, van Dokkum and his colleagues made follow-up observations with the Keck Observatory in Hawaii. Those observations showed that the streak was linked to a galaxy whose light took about 8 billion years — more than half the age of the universe — to reach Earth, the team said in a paper submitted to arXiv.org on February 9. Reported in The distance measurement lets the team calculate the length of the line: about 200,000 light-years.

It definitely knocked out a satellite.

“We considered a lot of explanations,” says van Dokkum, and the one that fits best is that what we’re seeing is a massive object, like a black hole, moving away from the Milky Way very quickly. “

Black holes themselves are invisible. But “if a black hole leaves a galaxy, it doesn’t go away on its own,” van Dokkum says. Some of the stars and gas that were gravitationally bound to the black hole escape with it. That gas will emit intense radiation that telescopes can detect. black hole path through Gas and dust in the outer regions of the Milky Way could also compress some of that gas into new stars, which would also be visible (Sn: 7/12/18,

Another possibility is that the line is a jet of radiation ejected by the galaxy’s central supermassive black hole. But that scenario would likely lead to a beam that is narrow when it is close to the galaxy and widens when it is far away. This streak does the opposite.

If it is a black hole, it may have been ejected from the center of the galaxy by interactions with one or two other black holes nearby. Almost every galaxy has a supermassive black hole at its center. When galaxies merge, their even central black holes eventually merge ,Sn: 3/5/21, If the conditions are right, he Mergers can “kick” the resulting black hole sending it flying at high speed (Sn: 4/25/22,

Alternatively, the black hole could have been ejected from a smashup between the three galaxies. When a third galaxy is involved in an ongoing merger, the three supermassive black holes jockey for position. One black hole may be ejected from the galactic smashup, while the other two slowly fly away in the other direction.

Van Dokkum thinks that’s what happened in this case. There are indications of a short, dim streak in the opposite direction from the bright, straight line.

More observations of this system, perhaps with the James Webb Space Telescope, are needed to confirm that it is indeed an ejected supermassive black hole, says Angus. More theoretical calculations of what a runaway supermassive black hole should look like would also help.

The discovery prompts Angus to search through archived data for more possible black hole streaks. “I wonder if there are more of these features sitting in someone’s data that might have been missed,” she says.

Van Dokkum does too. “Now that we know what to look for, these very thin streaks, it makes sense to go back to the Hubble data. We have 25 years of Hubble images that haven’t been searched for this purpose,” he says. “If there’s more to be found, I think we can do it.”