Webb finds 'sulfur' world
The James Webb Space Telescope has revealed a bizarre exoplanet 35 light‑years away with a permanent magma ocean and a sulfur‑rich atmosphere that likely contains hydrogen sulfide — meaning it could literally smell like rotten eggs. Astronomers are calling it a potential new class of planet because its extreme surface and atmospheric chemistry don't fit existing categories. (kxan.com) (dailygalaxy.com)
Designated L 98-59 d, the object is the subject of a Nature Astronomy paper led by Harrison Nicholls that was published online March 16, 2026 (nature.com). Researchers from the University of Oxford, the University of Groningen, the University of Leeds and ETH Zurich combined space-based transit spectroscopy with ground-based observations to constrain the planet’s atmosphere and interior (ox.ac.uk). Their coupled atmosphere–interior models infer an early bulk sulfur plus hydrogen inventory exceeding 1.8% by mass and predict in‑situ photochemical production of SO2 in an H2 background as an explanation for the observed spectral features (nature.com). Parameters used in the study include a radius of roughly 1.5–1.6 Earth radii, a mass on the order of ~2.1–2.3 Earth masses and a bulk density near 3.45 g cm−3, with the planet completing an orbit in about 7.5 days. The paper’s models require a global molten silicate layer extending thousands of kilometres that can act as a long‑term reservoir for sulfur, allowing volatile exchange between mantle and atmosphere over billions of years ( ). The authors explicitly present L 98-59 d as a candidate first member of a broader population of gas‑rich, sulphurous super‑Earths, and the Nature paper’s accepted manuscript lists receipt 29 May 2025 and acceptance 18 February 2026 ( ).
