Tau Ceti e, also called 52 Ceti e, is a doubtfulexoplanet candidate proposed to be orbiting Tau Ceti, first detected in 2012 by statistical analyses of the star's variations in radial velocity obtained using HIRES, AAPS and HARPS. Its possible properties were refined in 2017, where it was one of two planets recovered from new data, the other being Tau Ceti f. Studies published in 2021 and 2025 have been unable to confirm this planet.
It would orbit at a distance of (between the orbits of Venus and Mercury in the Solar System) with an orbital period of 168 days and has a minimum mass of 3.93 Earth masses. If Tau Ceti e possesses an Earth-like atmosphere, the surface temperature would be around . Based upon the incident flux upon the planet, a study of planetary habitability by Güdel et al. (2014) suggested that the planet lies outside of the conservative habitable zone defined by the runaway greenhouse limit, but within the optimistic habitable zone defined by the "recent Venus" limit.
In Andy Weir's 2021 science fiction novel, Project Hail Mary, along with the 2026 film, Tau Ceti serves as the primary present-day setting of the novel and Tau Ceti e is given the name "Adrian" (after the character from the Rocky franchise) and serves as the setting for the climax of the story.