Just 11.4 light-years from us, a planet orbits within its star’s habitable zone.
The planet, named Gl 725 B c, was added to NASA’s catalogue of confirmed exoplanets on August 20, 2026. Its discovery had been published earlier this year in Astronomy & Astrophysics. It orbits Gl 725 B, a red dwarf located about 3.5 parsecs from us.
Astronomers did not see it directly: they measured the tiny movements of its star caused by the planet’s gravitational pull. This method, called radial velocity, can notably be used to estimate a minimum mass. For Gl 725 B c, NASA’s catalogue indicates about 3.4 Earth masses, with an uncertainty of 0.7.
Artist’s view of a rocky exoplanet around a red dwarf. The habitable zone of these stars lies much closer to the star than the Sun’s.
Credit: NASA / JPL-Caltech
A complete orbit around its star takes 37.9 days. The planet is about 20.8 million kilometres from it. This distance would be far too small around the Sun, but Gl 725 B is much smaller and cooler than our star, with a surface temperature close to 3,106 °C.
The planet therefore receives an amount of energy compatible with the so-called habitable zone of its star. This term refers to the region where liquid water could exist on the surface under certain conditions.
Its estimated equilibrium temperature is about −58 °C, but this calculation does not take into account any possible atmospheric greenhouse effect. The actual temperature of its surface therefore remains unknown. Its composition is unknown as well, because the method used does not directly provide its radius.
The system’s proximity makes this discovery interesting. At 11.4 light-years, Gl 725 B c belongs to our immediate stellar neighbourhood on the scale of the Galaxy. Nearby planets offer better prospects for detailed observations than similar worlds located hundreds of light-years away.
The measurements were obtained with the SPIRou spectropolarimeter installed on the Canada-France-Hawaii Telescope. The team had to extensively correct traces left in the observations by Earth’s atmosphere. This correction brought out the weak periodic motion associated with the planet.
The same system also shows a signal corresponding to a candidate planet even closer to the star, Gl 725 B b. It would have at least 1.5 Earth masses and complete its orbit in 4.765 days. Additional observations may clarify the architecture of this system.