A 21-hour dip could help explain Tabby's star's decade-long dimming mystery
Since 2016, an ordinary-looking F-type star called KIC 8462852, nicknamed Tabby's star, has behaved anything but ordinarily. In a new study published in the Monthly Notices of the Royal Astronomical Society on July 6, researchers revisited this star to find out what is really causing its irregular dimming.
In July 2026, a study by Cristina Madurga-Favieres from the University of Warwick found evidence for a giant companion orbiting Tabby's star, explaining its decade-long dimming mystery. The team used NASA's Transiting Exoplanet Survey Satellite (TESS) to discover a symmetric, round-shaped transit lasting 21 hours and dimming the star's brightness by 1%.
If confirmed, this companion could be either a giant planet or a brown dwarf, with a mass between 5 to 14 Jupiter masses and a radius 1.7 times Jupiter's radius. The companion's gravitational perturbations may drive debris, such as exocomets or planetesimal fragments, into orbits around the star, producing the irregular dimming initially observed.
Future monitoring could confirm the companion's existence and provide insights into its role in Tabby's star's dimming patterns.
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