A star already famous for defying explanation may have a hidden companion large enough to account for its strangest behavior. Astronomers led by Cristina Madurga-Favieres at the University of Warwick say new data point to a giant object, somewhere between a large planet and a small brown dwarf, orbiting KIC 8462852, the star better known as Tabby’s Star or Boyajian’s Star. The proposed companion would carry about 9.4 times Jupiter’s mass and measure roughly 1.7 times Jupiter’s radius, circling a star located approximately 1,470 light-years away in the constellation Cygnus. The finding has not yet passed peer review, and at least one prominent astronomer argues the evidence is thin.
That caution matters because Tabby’s Star has burned researchers before. Its light curve, recorded by NASA’s Kepler mission, showed brightness dips of up to 20 percent, far deeper than an ordinary transiting planet could cause, and the anomaly drew global attention when astronomer Jason Wright floated the idea of a Dyson swarm: a theoretical array of energy-collecting structures built by an advanced civilization. Most astronomers preferred stranger but more natural explanations, from shifting dust clouds to swarms of disintegrating comets, and none of those ideas ever settled the question of what kept driving fresh material into the star’s path decade after decade. Even the more mundane rival explanations lacked a mechanism robust enough to keep the dimming going for a decade, which is exactly the gap a large, gravitationally disruptive companion could fill.
The Star That Broke Every Model
Tabby’s Star earned its reputation the hard way. Kepler’s data showed irregular dimming episodes that no single transiting body could explain, and the star’s odd behavior spawned a string of competing hypotheses, including clouds of dust, comet swarms and even a slowly melting exomoon. In 2021, astronomers confirmed the star has a binary companion, a red dwarf roughly half the mass of the sun, but that discovery did nothing to explain the dimming itself. The dips kept recurring without an obvious driver, and the star has been comparatively quiet in recent years, which left the underlying mystery unresolved rather than settled. A companion massive enough to disturb smaller bodies gravitationally would be the first concrete mechanism proposed since the alien-megastructure idea was largely ruled out. The star’s alternate name comes from astronomer Tabetha Boyajian, who first flagged the anomaly in the Kepler data and lent her name to the object as Boyajian’s Star.
What TESS and Ground-Based Telescopes Found
The new evidence comes from a reanalysis combining data from NASA’s Transiting Exoplanet Survey Satellite with archival radial velocity measurements gathered at the Nordic Optical Telescope, the European Southern Observatory’s 3.6-meter telescope, the Observatoire de Haute-Provence and the Leonard Euler telescope. Fresh analysis of the SOPHIE spectrograph data from Haute-Provence added further detail to the picture. The result describes a companion 9.4 times as massive as Jupiter and 1.7 times its radius, sitting in the size range where the boundary between a giant planet and a small brown dwarf blurs. The object would follow a slightly eccentric orbit averaging 2.35 astronomical units from the star and would run cold, at an estimated 268 Kelvin, or about 23 degrees Fahrenheit.
The transit signal that revealed the companion appeared as a single symmetric, round-shaped dip in the TESS light curve, a shape consistent with a spherical object passing in front of the star rather than an irregular cloud of dust. No transiting companion of this kind had ever been detected around Tabby’s Star before this analysis, which the paper’s authors describe as significant on its own, independent of whether it eventually explains the dimming.
A Possible Source for the Comet Swarms
The companion matters because it could supply a missing piece of an older theory. One long-standing idea holds that groups of exocomets, breaking apart as they pass close to the star, are responsible for the irregular light dips Kepler recorded. A large planet orbiting nearby could be the gravitational engine driving that process, nudging icy bodies out of stable orbits and sending them toward the star to disintegrate. The preprint argues that a companion’s presence would explain why such fragments are driven toward the star’s vicinity in the first place, since the object would perturb their orbits over time. TESS has already confirmed that this kind of debris field exists elsewhere, having identified at least 30 exocomets around the nearby star Beta Pictoris, so the mechanism is not without precedent.
Skepticism Awaiting Confirmation
Not every astronomer is convinced. Writing on the social platform Bluesky, Wright said he had examined many radial velocity curves over the years and that a key figure in the new paper does not show clear evidence of a giant planet or brown dwarf companion. He added that the authors had, at best, ruled out companions across most orbital periods rather than confirmed one, leaving only a small remaining parameter space where an object could still hide. Disagreement at the preprint stage is normal, since the paper has not yet been peer-reviewed. More data could settle the question either way. The James Webb Space Telescope or the Hubble Space Telescope could attempt to detect the companion directly, and the European Space Agency’s Gaia mission, which finished its observations and was decommissioned in 2025, is expected to release a fourth batch of data in December 2026 that could reveal more about what, if anything, is orbiting Tabby’s Star. Even if that release adds nothing definitive, the debate itself shows how far the study of this star has moved: a decade ago the leading theory involved an alien civilization, and today the competing explanations are a giant planet, a brown dwarf, or simple noise in the data.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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