Overview
- A peer‑reviewed paper published June 30, 2026, reports a revised mass of roughly 2.3 times Earth and a refined orbital period near 21 days for GJ 3378b, placing it in the host red dwarf’s habitable zone.
- The new measurements rely on radial‑velocity data from the Habitable‑zone Planet Finder on the Hobby‑Eberly Telescope and the NEID spectrometer on the WIYN Telescope, which together reduced earlier mass estimates near five Earths.
- The lower mass makes a rocky, super‑Earth composition more likely and increases the plausibility that the planet could support liquid surface water if it has retained an atmosphere.
- GJ 3378b sits close to the ‘cosmic shoreline,’ a boundary where strong stellar radiation can strip atmospheres, so whether it still holds an atmosphere is unknown with current telescopes.
- Astronomers plan continued ground‑based radial‑velocity follow‑up and expect that direct atmospheric study will depend on next‑generation facilities such as the Giant Magellan Telescope, the Extremely Large Telescope, and a future Habitable Worlds Observatory.