Astronomers at the Université de Montréal have confirmed a diverse cast of rocky worlds around a small star, L 98-59. The team, led by Charles Cadieux, used data from NASA’s TESS space telescope and ESO’s HARPS and ESPRESSO spectrographs to study the planetary system.
The researchers found five planets orbiting L 98-59, with four already known and confirmed. The fifth planet, designated L 98-59 f, was revealed through subtle variations in the star’s motion. This planet is located in the habitable zone, where conditions are suitable for liquid water to exist.
One of the inner planets, L 98-59 b, has a size comparable to Earth’s and half its mass. The other two inner planets may experience extreme volcanic activity due to tidal heating. Meanwhile, the third planet is unusually low in density, making it a “water world.”
The study also revealed nearly perfect circular orbits for the inner planets, a favorable configuration for future atmospheric detections.
“This system offers a unique laboratory to address some of the field’s most pressing questions,” said René Doyon, co-author of the study. “What are super-Earths and sub-Neptunes made of? Do planets form differently around small stars? Can rocky planets around red dwarfs retain atmospheres over time?”
The discovery confirms L 98-59 as a compelling nearby system for exploring the diversity of rocky planets and searching for signs of life. The team’s advanced analysis techniques and use of existing archival data allowed them to double the precision of mass and radius estimates for the known planets.
Their findings are set to be published in The Astronomical Journal, providing new insights into the nature and formation of small planets orbiting red dwarf stars.
Source: https://nouvelles.umontreal.ca/en/article/2025/07/22/a-udem-team-confirms-a-fifth-potentially-habitable-planet-around-l-98-59-a-red-dwarf-35-l