Named L 98-59F, this planet is a super-terrers not transiting with a minimum mass of 2.8 masses of earth on a 23 day orbit inside the habitable area of the small red dwarf L 98-59.
The impression of an artist of the planetary system L 98-59; In the foreground is the Super-Earth in the L 98-59F living area. Image credit: Benoît Gougeon / Udem.
L 98-59, also known as you-175, TIC 307210830, is a dwarf M about a third of the mass of the sun.
The system is located at around 34.5 light years in the southern constellation of Volans.
It has three transit exoplanets, identified by Tess in 2019, in compact orbits of 2.25, 3.7 and 7.45 days, with an external non-Transit planet of 12.8 days confirmed in 2021 using the ESO espresso spectrrograph.
These planets have a diverse range of sizes (0.8 to 1.6 terrestrial rays), masses (0.5 to 3 terrestrial masks) and probable compositions (such as the earth with possibly rich in water).
In a new study, the University of Montreal and the Trottier Institute for Research on exoplanets the astronomer Charles Cadieux and his colleague carefully reanalyzed Tess, Espresso, Harps and Webb.
They were able to determine the size and masses of the planets with unprecedented precision.
“We refine the rays of L 98-59B, C and D to 0.84 terrestrial rays, 1.33, 1.63, respectively,” they said.
“We also report updates of 0.46 terrestrial masses for L 98-59B, 2 for L 98-59C and 1.64 for L 98-59D, and a minimum mass of 2.82 for L 98-59e.”
Astronomers have also confirmed the existence of a fifth planet, L 98-59F, in the living area of the star, where the conditions could allow liquid water to exist.
“Finding a temperate planet in such a compact system makes this discovery particularly exciting,” said Dr. Cadieux.
“It highlights the remarkable diversity of exoplanetary systems and strengthens the case to study the potentially habitable worlds around low -mass stars.”
“These new results paint the most complete image we have ever had from the fascinating system L 98-59,” he added.
“This is a powerful demonstration of what we can achieve by combining data from space telescopes and high precision instruments on earth, and it gives us key objectives for future atmospheric studies with the NASA / ESA / CSA James Webb space telescope.”
The refined measurements reveal almost perfect circular orbits for interior planets, a favorable configuration for future atmospheric detections.
“With its diversity of rocky worlds and a range of planetary compositions, L 98-59 offers a unique laboratory to answer some of the most urgent questions in the field: what are the super-neptums made of” planets are formed in small stars? ” said Professor of the University of Montreal, René Doyon, director of the Trottier Institute for Research on Exoplanets.
The team’s document will be published in the Astronomical review.
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Charles Cadieux and al. 2025. Detailed architecture of the L 98-59 system and confirmation of a fifth planet in the habitable area. AJin press; Arxiv: 2507.09343
