Astronomers have refined the measurements of a planet orbiting in the habitable zone of a nearby star, concluding that it is about 2.3 times the mass of Earth and receives roughly 90 percent as much radiation from its star as Earth gets from the Sun. The world, GJ 3378 b, lies about 25 light-years away in the constellation Camelopardalis, according to reports in Sci.News and Space.com describing the study.
The planet was first detected in 2024, but a fresh analysis using two spectrographs shortened its estimated orbital period from about 24.7 days to 21.45 days and lowered its minimum mass, Tech Explorist reported. The lower mass makes it more likely to be a rocky 'super-Earth' than a gas-rich mini-Neptune, while its position in the star's habitable zone — the range of orbits where liquid water could exist on a surface — was preserved.
The findings were published in The Astrophysical Journal, according to the outlets covering the work. The study was led by researchers including Paul Robertson of the University of California, Irvine, with co-authors from institutions including the University of Texas at Austin and the University of Pennsylvania, Tech Explorist and Sci.News reported.
How the planet was pinned down
The team refined the planet's properties using the Habitable-zone Planet Finder on the Hobby-Eberly Telescope in Texas and the NEID spectrometer on the WIYN Telescope at Kitt Peak in Arizona, Sci.News reported. Both instruments detect planets by measuring the tiny gravitational wobble a world induces in its host star, a technique known as the radial-velocity method.
Its host, Gliese 3378, is a faint red dwarf — the most common type of star in the galaxy. Robertson said the planet receives 'just enough' starlight 'to maintain the surface pressures at which you can have liquid water,' according to Tech Explorist, and described it as 'one of our closest cosmic neighbors.'
Why the atmosphere question matters
Researchers cautioned that sitting in the habitable zone does not make a planet habitable. Sci.News reported that GJ 3378 b lies near what scientists call the 'cosmic shoreline,' the boundary beyond which stellar radiation can strip a planet's atmosphere away — leaving open the central question of whether this world has retained an atmosphere at all.
Red dwarfs are known to emit strong flares early in their lives, and scientists have debated for years whether rocky planets closely orbiting such stars can hold onto their air. Gogod James, a student in Robertson's group, said that if a habitable-zone planet 'has a proper atmosphere, we can justify further research looking for biosignatures,' Tech Explorist reported, referring to chemical signs that could indicate life.
What to watch
The outlets described GJ 3378 b as the kind of nearby target astronomers hope to study in detail with future observations, though the reporting did not specify a confirmed telescope schedule. Follow-up work capable of detecting and characterizing any atmosphere would be the decisive next step; until then, the planet remains an intriguing but unconfirmed candidate rather than a demonstrated second Earth.