Super-Earth Discovered in the Habitable Zone of a Nearby Red Dwarf

Madrid, March 12, 2025 (Lusa) -- An international team of scientists has detected a super-Earth orbiting in the habitable zone of GJ 3998, a nearby red dwarf located 59 light-years away.

The new planet, called GJ 3998 d, is the third planet found in this system, the Institute of Astrophysics of the Canary Islands (IAC) highlighted in a statement on Tuesday.

"GJ 3998 d is a welcome addition to the planetary census of our cosmic neighborhood," said Atanas Stefanov, a La Caixa Foundation-funded PhD student at the IAC and the University of La Laguna (ULL), and lead author of the study, published in the journal Astronomy & Astrophysics.

This super-Earth appears to be in the habitable zone of one of the closest stars to the Sun.

"This gives us one more reason to continue searching for habitable planets around us," Stefanov stressed.

The newly discovered planet, GJ 3998 d, is a super-Earth with a mass six times that of Earth, is in the "optimistic" habitable zone of its star and completes an orbit every 41.8 days.

At this distance, GJ 3998 d receives only 20% more stellar radiation compared to what Earth receives from the Sun.

"GJ 3998 is significantly smaller and cooler than the Sun, which shifts the habitable zone closer to the star," explained Alejandro Suárez Mascareño, IAC researcher and co-author of the study.

"Although it is certainly different from Earth, if the planet is rocky, it may be capable of hosting liquid water on its surface, one of the main requirements for life," said Jonay I. González Hernández, an IAC researcher and also a co-author.

The proximity of this system to the Sun makes GJ 3998 d an attractive candidate for atmospheric characterization.

"It should be possible to test for the presence of an atmosphere and search for oxygen using the future ANDES spectrograph on ESO's Extremely Large Telescope (ELT). GJ 3998 d would also be a good target for the future 50-metre Exo Life Finder (ELF) telescope, led by the IAC, which will search for biomarkers in exoplanet atmospheres," highlighted Rafael Rebolo, IAC researcher and co-author of the study.

The discovery is part of the HADES program, an international effort to explore planetary systems around red dwarfs, using the Telescopio Nazionale Galileo (TNG) at the Roque de los Muchachos Observatory on La Palma.

Red dwarfs are stars smaller and cooler than the Sun and make up almost three-quarters of the stellar population in our galaxy, the IAC also explained.

Their low mass and abundance make them prime targets in the search for low-mass planets, and GJ 3998, one of these red dwarfs, has been of particular interest to the community due to its proximity (59 light-years) and moderate stellar activity. A light year is about 9.46 trillion kilometers.

A previous study by the same team in 2016 had already detected two planets, so the presence of an additional signal in the data prompted continued observations and a reanalysis of the dataset.