A new search of TESS observations is putting numbers on a difficult question: how often do planets orbit a pair of red dwarf stars? A preprint posted October 15, led by Dominic Oddo, reports one new planet-sized candidate in a sample of eclipsing binaries containing two M dwarfs.
The team used a custom algorithm to find individual planetary transits, then tested the survey’s sensitivity and accounted for gaps in its observing coverage. The result is not a confirmed new planet or a precise population count.
For planets with radii between two and 16 times Earth’s and orbital periods up to 600 days, the authors obtain a 95 percent confidence upper limit of 33 percent if planetary and stellar orbits share a plane. Assuming instead randomly oriented planetary orbits raises that limit to 40.2 percent. These are ceilings under specified assumptions, not evidence that one-third of red-dwarf binaries host such planets. The study has been submitted to AAS journals.
Two moving targets
Finding these systems requires favorable geometry. A transit is a temporary loss of starlight when a planet passes in front of a star. In a circumbinary system, both stars also move around each other, complicating the timing and appearance of those crossings.
A NASA account of the 2021 discovery of TIC 172900988 b illustrates the problem. That giant planet takes roughly 200 days to orbit its two Sun-like stars, but the available TESS observations covered only about 30 days. The fortunate arrangement let astronomers see it cross both stars five days apart, while the stars themselves produced multiple eclipses.
That earlier discovery involved different kinds of stars, so it is not a direct comparison of population rates. It shows why a survey’s viewing angle and time coverage matter. A sparse list of detections cannot be read straightforwardly as a sparse population of planets.
Reporting checked October 20, 2026 (UTC). Catch-up coverage of the October 15 preprint.
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