27 New Candidate Planets Orbit Two Suns, Expanding Known Circumbinary Worlds

A team led by Associate Professor Ben Montet and PhD candidate Margo Thornton at the University of New South Wales announced the identification of 27 objects that could be planets orbiting binary stars. The candidates were detected in NASA’s Transiting Exoplanet Survey Satellite (TESS) data and lie between 650 and 18,000 light-years from Earth. The findings appeared in the *Monthly Notices of the Royal Astronomical Society* on 4 May 2026.

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Binary or multiple star systems make up over half of all stars in the Milky Way. Before this study, about 18 circumbinary planets were confirmed, mostly via the transit method that needs a precise orbital alignment with Earth. The new candidates therefore nearly double the catalog of known circumbinary worlds.

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Examining eclipse timing variations in 1,590 binaries, the team used apsidal precession—subtle orbital shifts—to detect timing changes caused by a third body’s gravity. After correcting for stellar rotation and mutual gravitation, 36 systems showed unexplained shifts; 27 match planetary-mass objects.

The Guardian

Twenty-seven candidates lie 650–18,000 ly away and likely range from Neptune-size to ten Jupiter masses. The study examined 1,590 binaries, finding 36 with anomalous eclipse timing. Before this work, about 18 circumbinary planets were known, versus over 6,000 exoplanets around single stars.

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Montet likened detecting faint signals near bright stars to “seeing a candle right next to a big street light.” Thornton said precise eclipse monitoring can reveal hidden companions. Astrophysicist Sara Webb called the technique “very clever” and said it could expand the circumbinary inventory and aid habitability studies.

The Guardian

Spectral analysis is needed to confirm planetary status, leaving mass classification uncertain; some objects may be brown dwarfs or low-mass stars. No composition or atmospheric measurements exist yet.

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• “There are many things in astronomy that aren’t very tangible,” — Ben Montet, UNSW

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• “If we monitor the exact timing of these eclipses… that can tell us that there’s something else going on in the system,” — Margo Thornton, UNSW

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• “It’s just a matter of: what is the mass of it? Is it a planet? Is it a brown dwarf? Is it a star?” — Margo Thornton, UNSW

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• “[But] a planet like Tatooine could potentially exist where there is that sweet spot between its orbit of the two stars – where it’s not too hot and it’s not too cold.” — Sara Webb, Swinburne

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If confirmed, these worlds would broaden knowledge of planet formation in binaries and provide test cases for extreme climate modeling. The success of eclipse-timing analysis suggests TESS archives and upcoming missions could reveal more circumbinary planets, refining their galactic frequency.

The Guardian