Jul 24, 2025 05:56 AM
https://www.eurekalert.org/news-releases/1092112
INTRO: A team led by the Trottier Institute for Research on Exoplanets (IREx) has achieved the most precise study to date of the L 98-59 planetary system, and confirmed the existence of a fifth planet in the star’s habitable zone, where conditions could allow liquid water to exist.
Volcanic planets, a sub-Earth, and a water world. L 98-59, a small red dwarf located just 35 light-years from Earth, hosts three small transiting exoplanets discovered in 2019, thanks to NASA's TESS space telescope, and a fourth planet revealed through radial velocity measurements with the European Southern Observatory's ESPRESSO spectrograph. All four planets orbit their parent star in a compact orbital configuration, all at distances five times closer than Mercury is to the Sun.
By carefully reanalyzing a rich set of observations from ground-based and space-based telescopes, a team led by Université de Montréal and Trottier Institute for Research on Exoplanets (IREx) researcher Charles Cadieux has determined the planets’ sizes and masses with unprecedented precision.
“These new results paint the most complete picture we’ve ever had of the fascinating L 98-59 system,” said Cadieux. “It’s 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 targets for future atmospheric studies with the James Webb Space Telescope [JWST].”
All planets in the system have masses and sizes compatible with the terrestrial regime. The innermost planet, L 98-59 b, is only 84% of Earth’s size and about half its mass, making it one of the rare sub-Earths known with well-measured parameters.
The two inner planets may experience extreme volcanic activity due to tidal heating, similar to Jupiter’s volcanic Moon, Io, in the Solar System. Meanwhile, the third, unusually low in density, may be a “water world,” a planet enriched in water unlike anything in our Solar System.
The refined measurements reveal nearly perfectly circular orbits for the inner planets, a favourable configuration for future atmospheric detections.
“With its diversity of rocky worlds and range of planetary compositions, L 98-59 offers a unique laboratory to address some of the field’s most pressing questions: 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?” adds René Doyon, co-author of the study, who is a professor at UdeM and the Director of IREx... (MORE - details, no ads)
PAPER: http://dx.doi.org/10.48550/arXiv.2507.09343
INTRO: A team led by the Trottier Institute for Research on Exoplanets (IREx) has achieved the most precise study to date of the L 98-59 planetary system, and confirmed the existence of a fifth planet in the star’s habitable zone, where conditions could allow liquid water to exist.
Volcanic planets, a sub-Earth, and a water world. L 98-59, a small red dwarf located just 35 light-years from Earth, hosts three small transiting exoplanets discovered in 2019, thanks to NASA's TESS space telescope, and a fourth planet revealed through radial velocity measurements with the European Southern Observatory's ESPRESSO spectrograph. All four planets orbit their parent star in a compact orbital configuration, all at distances five times closer than Mercury is to the Sun.
By carefully reanalyzing a rich set of observations from ground-based and space-based telescopes, a team led by Université de Montréal and Trottier Institute for Research on Exoplanets (IREx) researcher Charles Cadieux has determined the planets’ sizes and masses with unprecedented precision.
“These new results paint the most complete picture we’ve ever had of the fascinating L 98-59 system,” said Cadieux. “It’s 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 targets for future atmospheric studies with the James Webb Space Telescope [JWST].”
All planets in the system have masses and sizes compatible with the terrestrial regime. The innermost planet, L 98-59 b, is only 84% of Earth’s size and about half its mass, making it one of the rare sub-Earths known with well-measured parameters.
The two inner planets may experience extreme volcanic activity due to tidal heating, similar to Jupiter’s volcanic Moon, Io, in the Solar System. Meanwhile, the third, unusually low in density, may be a “water world,” a planet enriched in water unlike anything in our Solar System.
The refined measurements reveal nearly perfectly circular orbits for the inner planets, a favourable configuration for future atmospheric detections.
“With its diversity of rocky worlds and range of planetary compositions, L 98-59 offers a unique laboratory to address some of the field’s most pressing questions: 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?” adds René Doyon, co-author of the study, who is a professor at UdeM and the Director of IREx... (MORE - details, no ads)
PAPER: http://dx.doi.org/10.48550/arXiv.2507.09343