L 98-59 d (TOI-175 d) is an exoplanet orbiting the star L 98-59 34.6 light years from Earth. L 98-59 d is the third, potentially fourth, planet in its system. Its discovery was announced along with L 98-59 b and c in 2019 by the Transiting Exoplanet Survey Satellite (TESS). L 98-59 d is a super-Earth having a mass of 1.64 M🜨 and has a radius of 1.627 R🜨. It takes 7.450729 days to orbit L 98-59 and orbits at a distance of 4.94% Earth's orbit and has one of the least eccentric orbits in its system with an eccentricity of 0.006. The James Webb Space Telescope (JWST) observations of a planet found with an atmosphere made of hydrogen, hydrogen sulfide, and sulfur dioxide and also found a lava ocean on its surface.
Atmosphere In 2026, the JWST discovered a cloud-free atmosphere around L 98-59 d made of hydrogen, hydrogen sulfide and sulfur dioxide.
Magma ocean The same study that found an atmosphere around this planet found a molten surface made of lava with a temperature of 1900°C. The Guardian
Formation L 98-59 d formed as a sub-Neptune about 5 billion years ago and its star stripped its atmosphere away. L 98-59 d has an abundance of hydrogen, hydrogen sulfide and sulfur dioxide and over time due to volcanic activity formed an atmosphere with the same elements. L 98-59 d has a core mass of 66% Earth's total mass. Its core is 55% of the radius of Earth.https://doi.org/10.1038/s41550-026-02815 The planet L 98-59 d we see today is the dying remnant of a mini-Neptune in the process of losing its atmosphere and becoming airless.
References