L 98-59 b
Terrestrial planet orbiting L 98-59
From Wikipedia, the free encyclopedia
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.[2] It orbits L 98-59, a red dwarf star 34.6 light-years away in the constellation Volans. There are at least 4 (possibly 5) other planets in the system: L 98-59 c, d, e, f and the unconfirmed ".06".[2][4] Its discovery was announced on 27 June 2019 in The Astronomical Journal[1] and in a NASA press release. It was the smallest planet discovered by TESS[5] until the discovery of LHS 1678 b,[6] and was the lowest-mass planet whose mass had been measured using radial velocities[2] until Proxima Centauri d was found in 2022.[7]
Artist's impression and size comparison with Earth and Mars | |
| Discovery[1] | |
|---|---|
| Discovery date | March 2019 |
| Transit | |
| Orbital characteristics[2] | |
| 0.02191+0.00080 −0.00084 AU | |
| Eccentricity | 0.103+0.117 −0.045 |
| 2.2531136+0.0000012 −0.0000015 d | |
| Inclination | 87.71°+1.16° −0.44° |
| Semi-amplitude | 0.56±0.16 m/s[3] |
| Star | L 98-59 |
| Physical characteristics[2] | |
| 0.850+0.061 −0.047 R🜨 | |
| Mass | 0.47+0.13 −0.15 M🜨[3] |
Mean density | 4.3+1.2 −1.9 g/cm3[3] |
| Temperature | 627+33 −36 K (354 °C; 669 °F, equilibrium) |
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.[5] The temperature of the planet detected by TESS is 330 °C.[8] In 2022, transmission spectroscopy indicated that the planet has either no atmosphere or an opaque atmosphere with high-altitude hazes.[9]
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.[10]