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A runaway supermassive black hole escaped the cosmic Owl Galaxy, leaving a trail of stars in its wake. |Image credit: Li et al/Robert Lea (created using Canva)
Astronomers using the James Webb Space Telescope (JWST) have made a truly incredible discovery: a runaway black hole 10 million times larger than the sun, hurtling through space at an astonishing 2.2 million miles per hour (1,000 kilometers per second).
Not only does this make it the first confirmed runaway supermassive black hole, but the object is also one of the fastest-moving objects ever detected, orbiting its home planet – a pair of namedcosmic owl” at 3,000 times the speed of sound at Earth’s sea level. If that wasn’t shocking enough, the black hole is pushing a galaxy-sized “bow shock” of material forward while trailing a 200,000 light-year tail behind it, in which gas is accumulating and triggering star formation.
“It’s incredible!” Pieter van Dokkum, leader of the discovery team at Yale University, told Space.com. “The force required to eject such a massive black hole from its home is enormous. Yet, it was predicted that such an escape should happen!”
supermassive black holeWith masses up to billions of times that of the Sun, they are usually located at the centers of their host galaxies, where they dominate with their immense gravitational pull. The incredible speed of this supermassive black hole means it is about 230,000 light-years from its point of origin.
“This is the only black hole discovered so far away from its homeworld,” Van Dokum said. “That makes it the best candidate. [for a] Runaway supermassive black holes, but confirmation lacking. All we really have is a continuity that is hard to explain otherwise. Through JWST, we have now confirmed that there is indeed a black hole at the tip of the streak, and that it is accelerating away from its former host. “
How to spot a runaway
This now confirmed runaway supermassive black hole is van Dokkum and colleagues first found Go back to 2023 and use Hubble Space Telescope, It spotted what appeared to be the wake of a massive object traveling through space. Of course, like all black holes, this runaway is limited by a one-way light-trapping surface called the event horizon, making it difficult to detect.
“A black hole is black and difficult to detect as it passes through empty space,” Van Dokum said. “We discovered this object because of the impact the black hole’s passage has on its surroundings: We now know that it creates a shock wave in the gas it passes through, and it is this shock wave that we see, as well as the wake of the shock wave behind the black hole.” “With JWST, we found that there is a huge displacement of gas at the tip of the wake, and the black hole is pushing against it. The impact signal is very clear, and there is no doubt what is happening here.” Gas is being pushed away from the supermassive black hole at hundreds of thousands of miles per hour (hundreds of kilometers per second), a dynamic signature the team saw with JWST.
Hubble image showing a now confirmed runaway supermassive black hole and its wake, investigated by JWST | Image credit: van Dokkum et al. (2025)/arXiv
“The speed at which the gas is expelled is directly related to the speed of the black hole, which is how we determine the black hole’s speed based on the JWST data,” Van Dokum said. “It is moving at about 1,000 kilometers per second, faster than any other object in the universe. It is this high speed that allows the black hole to escape the gravitational pull of its predecessor.”
How do supermassive black holes “go out of control”?
Van Dokum explained that there are two possible mechanisms that could cause a supermassive black hole to be ejected from the center of its galaxy. Both conditions begin when two galaxies collide and begin to merge, each shattering its own supermassive black hole. Both mechanisms are activated when a supermassive black hole reaches the center of a newly formed galaxy.
“The first mechanism is that two black holes merge with each other and gravitational radiation [gravitational waves] The material released in the merger gives the newly formed black hole a powerful impact. Van Dokum said this kick could produce speeds of 1,000 kilometers per second, enough to eject a black hole. The second is the three-body interaction. This happens when one of the two galaxies has a pair double black hole in its center. When a third black hole enters the binary system, it becomes unstable and one of the three black holes is kicked out of the system. “
The team believes this is the first explanation for a runaway supermassive black hole in this situation. This would result in a lack of supermassive black holes at the center of galaxies, which Van Dokum said is unlikely to have much of an impact on galaxies. However, this runaway supermassive black hole could have a huge impact on any other galaxies it encounters as it hurtles through space.
“An encounter with another galaxy would be pretty spectacular, mostly because of the massive, galaxy-sized shock wave that precedes the black hole,” Van Dokum continued. “When this shock wave encounters the dense gas of another galaxy, it compresses and impacts that gas and potentially forms many new stars. It’s going to be quite a show!”
Fortunately, the two rings of galaxies that make up the Cosmic Owl are about 9 billion light-years away, which means that even if this runaway cosmic titan is headed in our direction, we don’t have to worry about it reaching us.
Mergers between galaxies are common and occur multiple times during the lifetime of a single galaxy. This means that ejected supermassive black holes may also be common, although the number of black holes varies depending on how these collisions are modeled.
Van Dokum said: “Mergers occur frequently in the lifetime of galaxies; every galaxy the size and mass of the Milky Way undergoes several mergers in its lifetime. So black hole binaries should form with great regularity. We don’t know how fast, if at all, these binaries merge, and how often the resulting kick removes the black hole.” “My point is empirical: now that we know how to look for them, we can find other examples, and then we can answer the question directly from the data by counting the number of escapes. Importantly, black hole escapes have so far existed purely in the realm of theory.” Although theory predicted runaway supermassive black holes before this discovery confirmed their existence, that doesn’t mean the discoveries didn’t come with some unexpected twists.
“Everything about this study surprised me! I never thought I would see something like this, and confirming this with JWST is incredible,” Van Dokum said. “What we haven’t fully realized yet is how much of an impact these escaping black holes have on the gas they pass through. Many new stars then form from the impacted gas, with masses around 100 million times that of the Sun. This mode of star formation was previously unknown, and it results in a trail of stars far away from the Milky Way, seemingly forming in the vacuum of space.”
The team’s next obvious step is to find more examples of runway black holes, the Yale researcher explained.
“You need space-based imaging to see them: the wake stands out to us because it is a very thin streak, whereas in ground-based images it would be blurred beyond recognition,” van Dokum explains. “Fortunately, Hubble-quality wide-field imaging is coming thanks to the Roman Space Telescope and the slightly blurry Euclid Telescope. Using machine learning algorithms to find thin streaks in the Roman data will be a cool project!”
The team’s research has been submitted to The Astrophysical Journal Letters and is now available as a peer-reviewed paper arXiv.
