Overview
- A study published on Tuesday June 30, 2026, led by Paul Robertson used radial‑velocity data from the HPF and NEID spectrometers to revise GJ 3378b’s minimum mass to about 2.3 times Earth and its orbital period to roughly 21 days.
- The updated orbit places the planet well inside its red dwarf star’s habitable zone so it receives about 90 percent of the starlight Earth gets, a level that could allow liquid water if the planet has an atmosphere.
- GJ 3378b does not transit its star, which prevents current transit‑spectroscopy methods from probing its air and leaves direct evidence of any atmosphere unknown.
- The planet sits near the so‑called cosmic shoreline, the threshold where stellar radiation tends to strip atmospheres, so its proximity to an active red dwarf makes atmospheric retention uncertain and hard to resolve with existing telescopes.
- First reported in 2024 with a higher mass that suggested a mini‑Neptune, the 2026 revision at 25 light‑years away recasts GJ 3378b as a high‑priority nearby target for future direct‑imaging and spectroscopy by facilities such as GMT, ELT and NASA’s Habitable Worlds Observatory.