Physicists Propose New Way to Spot Supermassive Black Hole Pairs

Repeating, magnified flashes of starlight could reveal hidden black hole binaries

Published on Feb. 14, 2026

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Researchers at the University of Oxford and the Max Planck Institute for Gravitational Physics have proposed a new method to detect tight supermassive black hole pairs. Their idea suggests these hidden binaries could reveal themselves through repeating, magnified flashes of starlight, which they call "quasiperiodic lensing of starlight" (QPLS). As the binary orbits and its separation shrinks, the changing caustic curve could sweep across stars in the host galaxy, briefly boosting their brightness by up to a million times.

Why it matters

Finding tight supermassive black hole binaries has proven challenging, as they are difficult to detect using traditional methods that rely on gas-fed active galactic nuclei. This new approach could help widen the census of these elusive systems, especially in quieter galaxies where other techniques struggle. It could also provide an "early warning" for future gravitational wave detections, allowing astronomers to study these systems in multiple wavelengths.

The details

The researchers modeled the binary as two point-mass lenses and tracked how the caustics move as the orbit tightens. They estimate a star with a radius of 10-1000 solar radii could be magnified by 10,000-1 million times, making an ordinary star appear as a powerful central source. The characteristic brightening time is about 16 hours, and they predict 1-50 [190-5000] QPLS sources in systems with periods below 10 [40] years at redshift z < 0.3.

  • The paper was published on February 14, 2026.

The players

Miguel Zumalacárregui

A researcher at the Max Planck Institute for Gravitational Physics.

Bence Kocsis

A professor in the Department of Physics at the University of Oxford and a co-author of the study.

Hanxi Wang

A graduate student who works in Professor Kocsis' group and led the study.

Zwicky Transient Facility

A wide-field survey that the researchers mention as a potential tool for detecting the proposed QPLS signals.

Vera C. Rubin Observatory

A future observatory that the researchers say could monitor roughly 2 x 10^10 galaxies over ten years, with time resolution of about days in a single filter.

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What they’re saying

“Supermassive black holes act as natural telescopes. Because of their enormous mass and compact size, they strongly bend passing light. Starlight from the same host galaxy can be focused into extraordinarily bright images, a phenomenon known as gravitational lensing.”

— Miguel Zumalacárregui, Researcher, Max Planck Institute for Gravitational Physics

“The chances of starlight being hugely amplified increase enormously for a binary compared to a single black hole.”

— Bence Kocsis, Professor, University of Oxford Department of Physics

“As the binary moves, the caustic curve rotates and changes shape, sweeping across a large volume of stars behind it. If a bright star lies within this region, it can produce an extraordinarily bright flash each time the caustic passes over it. This leads to repeating bursts of starlight, which provide a clear and distinctive signature of a supermassive black hole binary.”

— Hanxi Wang, Graduate Student, University of Oxford

“The prospect of identifying inspiraling supermassive black hole binaries years before future space-based gravitational wave detectors come online is extremely exciting. It opens the door to true multi-messenger studies of black holes, allowing us to test gravity and black hole physics in entirely new ways.”

— Bence Kocsis, Professor, University of Oxford Department of Physics

What’s next

The researchers note that more realistic light curve modeling and the effects of gas around the binary will need to be addressed to fully develop this technique. They also highlight the need for wide-field surveys like the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope to have the necessary time resolution and depth to detect these quasiperiodic lensing signals.

The takeaway

This proposed method of using repeating, magnified flashes of starlight could significantly expand the search for elusive, tight supermassive black hole binaries, especially in quieter galaxies where other techniques have struggled. If successful, it would open up new avenues for multi-messenger astronomy and testing our understanding of gravity and black hole physics.