L 98-59 (TOI-175, TIC 307210830) is a red dwarf star located in the constellation of Volans, at a distance of , as measured by the Gaia spacecraft.
Broadband photometry shows that it is an M dwarf star, redder, smaller and fainter than the Sun. It has three confirmed terrestrial-size planets in transit, which were announced in 2019 by the Transiting Exoplanet Survey Satellite (TESS), as well as two additional non-transiting planets, for a total of five known planets. The outermost planet is in the habitable zone.
Planetary system The planets L 98-59 b, c, and d were discovered in 2019 by TESS. The non-transiting potential super-Venus planet L 98-59 e was discovered in 2021, along with indications of the presence of L 98-59 f, another non-transiting super-Earth located in the system's habitable zone. In 2025, the planet f was confirmed, and an additional planet candidate orbiting interior to planet b was detected.
The two innermost confirmed planets, L 98-59 b and c, as well as L 98-59 e are possibly hot rocky planets. L 98-59 d has a low density, around versus for Earth, indicating large amounts of volatiles.
Atmosphere characterization In September 2021, suggested tests of the abilities of the Hubble Space Telescope and the James Webb Space Telescope (JWST) to detect and describe the atmospheric features of the three inner planets were reported. In 2022, Hubble observations of three transiting planets found with no clear evidence of atmospheres, with high mean molecular weight atmospheres, cloudy or hazy atmospheres, or no atmospheres all being consistent with the observed flat spectra. However, the JWST did find evidence of sulfur dioxide, hydrogen, and hydrogen sulfide for planets b and d, suggesting that both are sulfur-rich volcanic worlds with strong tidal heating, and may contain a global internal magma ocean. A 2026 study was able to confirm the presence of hydrogen sulfide for planet d using ground-based telescope.
Gallery
See also List of potentially habitable exoplanets List of exoplanets discovered in 2019 TOI-700 d
References
External links New ESO observations show rocky exoplanet has just half the mass of Venus (ESO press release) TESS – Official Website Smallest exoplanet found so far (video; 1:53; NASA; June 2019)