Statistical study finds evidence for recoiling supermassive black holes in quasar population

Analysis of 100,000 quasars shows a correlation between dust obscuration and black hole speed, consistent with theoretical predictions of merger remnants kicked from galactic centres

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Published22 October 2026

Updated22 October 2026

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A new statistical analysis of about 100,000 quasars has found a correlation between dust obscuration and the speed of supermassive black holes, providing evidence for a population of recoiling black holes that have been kicked from their galactic centres after a merger. The findings, published in Monthly Notices of the Royal Astronomical Society, support theoretical predictions that uneven gravitational waves can drive the remnant of a black hole merger into a pendulum-like oscillation, leaving a trace in the light from surrounding gas and dust.

When galaxies merge, their central supermassive black holes (SMBHs) are expected to eventually merge as well, releasing powerful gravitational waves. If those waves are emitted unevenly, the imbalance can give the merged black hole a recoil velocity between 360,000 km/h and 3.6 million km/h, kicking it away from the centre of the galaxy. The black hole does not escape the galaxy entirely but begins a pendulum-like swing, moving fastest near the centre and slowing at the ends of its arc.

Researchers led by Bence Bécsy of the University of Birmingham searched for a statistical signature of this process across a large population rather than looking for individual candidates, which have been difficult to confirm due to alternative explanations. Using data from the 16th release of the Sloan Digital Sky Survey, they analysed the light from some 100,000 quasars, the bright active nuclei of galaxies, looking for two pieces of information encoded in the light: velocity and dust extinction.

The broad line region (BLR) of gas moves with the black hole, while the narrow line region (NLR) remains behind, producing a Doppler shift between the two that reveals the black hole's speed. Meanwhile, dust near the galactic centre reddens the quasar's light more when the black hole is moving fastest. The team found that the most reddened quasars showed the largest velocity offsets, with the fastest-moving group having three times the obscured fraction of the slowest group.

"It is very difficult to prove that the black hole in a single quasar has been ejected, because other phenomena can produce similar signatures," said Bécsy. "What is new about our research is that, rather than looking for individual candidates, we searched statistically for traces of an entire population. This enabled us to identify a relationship consistent with theoretical predictions."

The authors caution that the correlation could also be explained by winds, viewing angle, or other effects. More definitive proof may come with the planned launch of the Laser Interferometer Space Antenna (LISA) in 2035, which could detect gravitational waves from such mergers. "If the signal is indeed caused by ejected black holes, then two supermassive black holes merged relatively recently in a significant proportion of quasars, meaning that these events are common," said co-author Zsolt Frei of the HUN-REN–ELTE Extragalactic Astrophysics Research Group. "This directly determines how many such events LISA may be able to detect."

Analysis

Why This Matters

The finding suggests that supermassive black hole mergers are common enough to leave a detectable statistical signal, directly informing expectations for the LISA gravitational wave observatory.
It provides a new way to study galaxy evolution and the dynamics of black hole mergers without needing to confirm individual candidates.
If confirmed, it would mean a significant fraction of quasars have recently experienced a black hole merger, altering our understanding of active galactic nuclei.

Background

Astronomers know that most large galaxies host a supermassive black hole at their centre. When galaxies collide, their black holes are expected to eventually merge as well, releasing gravitational waves. Theory predicts that if the waves are emitted unevenly, the merged black hole can be kicked away from the centre. Finding such recoiling black holes has been difficult because other phenomena, such as jets, winds, or viewing angle effects, can produce similar signatures. This study breaks from the individual-candidate approach and instead searches for a population-level correlation between dust obscuration and velocity offset, a signature predicted by recoil models.

Key Perspectives

The research team: They consider the correlation consistent with theoretical predictions of recoiling black holes and argue that it points to a common population of recent mergers. They are cautious, however, noting that alternative explanations exist. Skeptics: Winds, viewing angle, and other astrophysical effects could produce a similar correlation. Without direct detection of gravitational waves or unambiguous individual candidates, the interpretation remains debated. LISA mission planners: If recoiling black holes are common, LISA, set to launch in 2035, may detect many such merger events, providing direct confirmation and precise measurements.

What to Watch

The launch and operations of LISA, which can directly detect gravitational waves from supermassive black hole mergers.
Further statistical analyses using larger quasar surveys or additional spectral diagnostics to strengthen or refute the correlation.
Individual candidate studies that might confirm a recoiling black hole beyond reasonable doubt, possibly using high-resolution imaging of the host galaxy.

Sources

New Evidence for an Old Prediction: Recoiling Supermassive Black Holes · Universe Today
Supermassive black holes ejected from galactic centers? Quasar survey supports decade-old prediction · Phys.org - latest science and technology news stories

Checked

10 claims in this story checked against 1 source: 8 supported.

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Partly supportedThe headline says the study found evidence for recoiling supermassive black holes in the quasar population.Universe Today: “While the correlation we find might be evidence for a population of recoiling SMBHs, alternative explanations are possible”
SupportedThe analysis of about 100,000 quasars found a correlation between dust obscuration and black hole speed.Universe Today: “The researchers analyzed about 100,000 quasars in their work. ... Dust obscuration tracks black hole speed: the faster the black hole moves, the more likely its quasar is to be buried in dust”
SupportedThe correlation is consistent with theoretical predictions of merger remnants kicked from galactic centres.Universe Today: “Theoretical predictions state that if the waves aren't emitted equally in all directions—or aren't isometric—the imbalance can drive the merger remnant SMBH away from the galactic center with a powerful kick.”
Partly supportedThe opening says the correlation provides evidence for a population of recoiling black holes.Universe Today: “While the correlation we find might be evidence for a population of recoiling SMBHs, alternative explanations are possible”
SupportedThe study was published in Monthly Notices of the Royal Astronomical Society.Universe Today: “The research is " Statistical evidence for massive black hole recoils in active galactic nuclei ," and it's published in Monthly Notices of the Royal Astronomical Society.”
SupportedThe fastest-moving group had three times the obscured fraction of the slowest group.Universe Today: “the fastest group showing three times the obscured fraction of the slowest.”
SupportedBence Bécsy said it is difficult to prove a single quasar’s black hole was ejected because other phenomena can produce similar signatures.Universe Today: ““It is very difficult to prove that the black hole in a single quasar has been ejected, because other phenomena can produce similar signatures.””
SupportedThe authors say winds, viewing angle or other effects could explain the correlation.Universe Today: “Winds, viewing angle, or other effects could also explain it.”
SupportedLISA has a planned launch in 2035 and could provide more definitive proof by detecting gravitational waves from such mergers.Universe Today: “More definitive proof for recoiling SMBHs might arrive with LISA, the Laser Interferometer Space Antenna , after its planned launch in 2035.”
SupportedZsolt Frei said that if the signal is caused by ejected black holes, mergers occurred relatively recently in a significant proportion of quasars and are common.Universe Today: ““If the signal is indeed caused by ejected black holes, then two supermassive black holes merged relatively recently in a significant proportion of quasars, meaning that these events are common,” said Professor Zsolt Frei”