Gliese 251 is an early red dwarf star and the 74th closest star system to the Sun.
An artist's impression of the Gliese 251 system: Gliese 251c (left), its parent star (right), and the previously discovered planet Gliese 251b (center). Image credit: Michael Marcheschi/m2design.
Glass 251 is a bright M-dwarf star located at a distance of 5.58 parsecs (18 light years) in the constellation Gemini.
The star, also known as GJ 251, HD 265866 or Wolf 294, likely contains at least two super-Earths: Gliese 251b and Gliese 251c.
First discovered in 2020, Gliese 251b will have a mass of 3.85 Earth masses and an orbital period of 14.2 days.
The newly discovered exoplanet Gliese 251c has a mass of 3.84 Earth masses and an orbital period of 53.6 days.
“We've found so many exoplanets at this point that discovering a new one isn't that big of a deal,” said UC Irvine astronomer Paul Robertson.
“What makes it especially valuable is that its parent star is nearby, about 18 light-years away. From a cosmic perspective, it's practically next door.”
Gliese 251c was discovered using data from the Habitable Zone Planet Finder (HPF), a high-precision near-infrared spectrograph on the Hobby-Eberly Telescope at McDonald Observatory in Texas.
The planet's signal was further confirmed using the NEID spectrometer at Kitt Peak National Observatory in Arizona.
“With this system, we are on the cutting edge of technology and analysis,” said Design West Technologies data scientist Corey Byrd.
“Although its discovery is highly statistically significant, we are still determining the status of the planet due to the uncertainty of our instruments and methods.”
“We need the next generation of telescopes to see this candidate directly, but we also need investment in the community.”
Gliese 251c's proximity to Earth makes it an ideal target for future exploration with the upcoming Thirty Meter Telescope (TMT).
The large size of the TMT's mirrors could allow it to directly image faint exoplanets such as Gliese 251c and confirm the presence of water.
“TMT will be the only telescope with sufficient resolution to image exoplanets like this,” Dr Beard said.
“This is simply not possible with smaller telescopes.”
The team's results were published in the journal Astronomical Journal.
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Corey Beard etc.. 2025. Discovery of a nearby Super-Earth candidate habitable zone accessible to direct imaging. A.J. 170, 279; doi: 10.3847/1538-3881/ae0e20
