GJ 3378b
GJ 3378b is a super-Earth exoplanet orbiting the red dwarf gj-3378, 25 light-years away in the constellation Camelopardalis.
Habitability
Discovered in 2024 with an initial mass estimate of ~5 M⊕, GJ 3378b’s mass and orbit were refined in June 2026 using the Habitable-zone Planet Finder instrument on the Hobby-Eberly Telescope at McDonald Observatory: revised mass ~2.3 M⊕ and orbital period 21 days (down from 25). The lighter mass strengthens the case for a rocky composition, and the tightened orbit confirms its position within the star’s habitable zone — though the same tight orbit around a cool, small star exposes the planet to intense stellar radiation that could strip any atmosphere. It joins gj-887-d as a recently refined nearby M-dwarf habitable-zone candidate, and is a target for follow-up biosignature searches by next-generation observatories including the habitable-worlds-observatory.
See src-gj-3378b-habitability-2026-06.