JWST Discovers New Magma Ocean Exoplanet Type

Astronomers have identified a previously unknown type of exoplanet, characterized by a global ocean of molten magma and an atmosphere rich in sulfur compounds, using observations from NASA's James Webb Space Telescope. The planet, known as L 98-59 d, orbits a red dwarf star about 35 light-years from Earth and represents a distinct class of worlds that challenges existing planetary classifications.

The discovery, detailed in a study published on March 16, 2026, in Nature Astronomy, stems from an international team led by Harrison Nicholls of the University of Oxford. The researchers combined data from the James Webb Space Telescope, captured in 2024, with observations from ground-based telescopes to analyze the planet's properties. L 98-59 d is approximately 1.6 times Earth's size but has an unusually low density, suggesting a composition unlike typical small exoplanets. Its atmosphere contains significant amounts of hydrogen sulfide, a gas known for its rotten-egg odor, along with sulfur dioxide and other sulfur-based molecules.

Computer simulations developed by the team, which included scientists from the University of Groningen, the University of Leeds, and ETH Zurich,...