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Tabby's star may be orbited by a planetary-mass companion
By analyzing data from NASA's Transiting Exoplanet Survey Satellite (TESS) and conducting new radial velocity measurements, U.K. and French astronomers have found evidence that the mysterious Tabby's star may be orbited by an object about nine times more massive than Jupiter. The new findings are published on the preprint server arXiv.
Mysterious flickering star
KIC 8462852, also known as Tabby's star (after the discoverer Tabetha S. Boyajian), is a peculiar F3V main-sequence star showcasing deep, irregular flux variations of up to 20% in its light curve. The star is about 50% larger and more massive than the sun, with an effective temperature of 6,750 K. In 2021, it was found that Tabby's star is part of a binary system with a red dwarf companion, which is about half the size and mass of our sun.
Several hypotheses have been proposed to explain the irregular dips in the light curve of Tabby's star, including a family of exocomets or planetesimal fragments. It was even proposed that the flux variations could be caused by extraterrestrial megastructures, which was later debunked. However, the origin of these dips remains uncertain.
Now, a new study by astronomers led by Cristina Madurga-Favieres may bring us closer to disentangling this mystery. They suggest that Tabby's star is orbited by an object on the planet/brown dwarf boundary, which may somehow be involved in the observable variations.
"This work presents a symmetric round-shaped transit found in the TESS data of KIC 8462852, suggesting the existence of a companion, either a giant planet or a brown dwarf, around the star," the researchers wrote in the paper.
Possible companion object
According to the study, the companion would have a radius of about 1.7 Jupiter radii, a mass of around 9.4 Jupiter masses and a density of 2.2 g/cm3. It would be a cool object with an equilibrium temperature of 268 K, orbiting its host on a slightly eccentric orbit at a distance of some 2.35 AU.
The astronomers emphasize that the presence of such a companion would explain why, if the exocomets/planetesimals hypothesis is true, these bodies are driven to the vicinity of the star and break up, as it would orbitally perturb them.
However, more observations of the system are required to determine the final orbital period and confirm the presence of the companion. The paper's authors hope that the upcoming data release from Gaia DR4, planned for December 2026, will reveal the true nature of this object.
They add that observations with the James Webb Space Telescope (JWST) and the Hubble Space Telescope (HST) could be used to observe and study the primordial atmosphere of the companion. Such observations, along with the discovery of the next transit, would help disclose more information about the system.
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Publication details
Cristina Madurga-Favieres et al, Evidence for a giant companion orbiting Tabby's star, arXiv (2026). DOI: 10.48550/arxiv.2607.20643
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Citation: Tabby's star may be orbited by a planetary-mass companion (2026, July 28) retrieved 28 July 2026 from https://phys.org/news/2026-07-tabby-star-orbited-planetary-mass.html
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