A red dwarf star just 25 light-years from Earth is hosting a super-Earth sitting almost exactly where liquid water could survive on its surface — and astronomers didn’t just find it once. A team led by Paul Robertson, associate professor of astronomy at the University of California, Irvine, confirmed the planet’s existence using two independent spectrographs on two separate telescopes, an unusually strong evidentiary standard for a field where single-instrument radial-velocity detections are sometimes later retracted. The discovery, reported in The Astrophysical Journal, was announced by UC Irvine on 30 June 2026.
A super-Earth in the “sweet spot”
The planet, designated GJ 3378b, orbits a small, cool M-dwarf star roughly twice Earth’s diameter, with a minimum mass just over twice Earth’s — squarely in the “super-Earth” size class. What makes it newsworthy isn’t just its size but its position: it receives about 90% of the radiation that Earth receives from the Sun, placing it inside its star’s habitable zone, the orbital range where a rocky planet could plausibly hold liquid water. “This super-Earth gets about 90 percent of the radiation from its host star as Earth gets from its sun, so it’s right in the sweet spot,” Robertson said.
Why two instruments matter more than one
Planets this small are found indirectly, by measuring the tiny gravitational wobble they induce in their host star’s light — a technique called radial-velocity spectroscopy. The signal is faint enough, and the noise sources numerous enough (starspots, instrument drift, stellar activity), that single-instrument super-Earth detections in the literature have occasionally not held up. Robertson’s team avoided that trap by measuring the same wobble with two independent, purpose-built spectrographs: the Habitable-zone Planet Finder (HPF) on the Hobby-Eberly Telescope at McDonald Observatory in Texas, and the NEID spectrometer on the WIYN Telescope at Kitt Peak National Observatory in Arizona. Both instruments, built specifically to hunt for small planets around red dwarf stars, independently recovered the same periodic signal — a cross-validation step that functions as a real-time reproducibility check rather than a retrospective one, and gives the detection considerably more weight than a single dataset would.
Who did the work
The UC Irvine team included graduate student Gogod James alongside Robertson, working with Michael Endl and William Cochran of the University of Texas at Austin and McDonald Observatory, Gudmundur Stefansson of Schmidt Sciences, and Suvrath Mahadevan of Pennsylvania State University — a multi-institution collaboration spanning the two observatories that built and operate HPF and NEID. The research was funded by National Science Foundation Astronomy & Astrophysics Research Grants and NASA’s Interdisciplinary Consortia for Astrobiology Research program, reflecting the dual observational-astronomy and astrobiology framing of the search: NASA’s astrobiology funding line specifically supports the hunt for potentially habitable worlds, not just planet detection for its own sake.
What “habitable zone” does and doesn’t mean
Being in the habitable zone is a necessary condition for surface liquid water, not proof of it. GJ 3378b’s host star is a red dwarf — a class of star known for flare activity and tidally-locking planets in close orbits, both of which complicate the case for a genuinely Earth-like environment. Confirming the planet’s habitable-zone status is the beginning of a research program, not its conclusion: the next steps for planets like this typically involve atmospheric characterization, usually via transit spectroscopy if the geometry allows it, to determine whether an atmosphere — and any biosignature gases — is actually present.
What to watch
- Whether GJ 3378b transits its star from Earth’s vantage point, which would open the door to atmospheric spectroscopy with instruments like JWST.
- Further independent confirmation or refinement of the planet’s mass and orbital parameters as more radial-velocity data accumulates.
- How red-dwarf flare activity and tidal effects factor into ongoing habitability assessments for M-dwarf planets generally.
Source: UC Irvine News, “UC Irvine astronomers discover a new, Earth-like exoplanet,” 30 June 2026, reporting on a paper published in The Astrophysical Journal.
