L 98-59 b
L 98-59 b is an exoplanet having a size between that of the Earth and Mars and a mass only half that of Venus. It orbits L 98-59, a red dwarf star 34.6 light-years away in the constellation Volans. There are at least 4 other planets in the system: L 98-59 c, d, e, f and the unconfirmed ".06". Its discovery was announced on 27 June 2019 in The Astronomical Journal and in a NASA press release. It was the smallest planet discovered by TESS until the discovery of LHS 1678 b, and was the lowest-mass planet whose mass had been measured using radial velocities until Proxima Centauri d was found in 2022.
Characteristics
L 98-59 b orbits its star in 2.25 days and stays so close to the star that it receives 22 times more energy than Earth receives from the Sun. There are 4 confirmed planets in the system but they are not in the habitable zone of the host star. The temperature of the planet detected by TESS is 330 °C. In 2022, transmission spectroscopy indicated that the planet has either no atmosphere or an opaque atmosphere with high-altitude hazes.Transmission spectroscopy observations with the James Webb Space Telescope NIRSpec published in 2025 favor the presence of a sulfur dioxide atmosphere. This is likely driven by volcanism, implying that L 98-59 b experiences at least eight times as much volcanism and tidal heating as Io.