A new class of planet exists with oceans of magma

Space · Published 22 October 2026 Swipe more like this →

In short: Astronomers have long categorized small planets as either rocky gas-dwarfs or water-rich ice worlds. However, a discovery 35 light-years away suggests our classification system is too simple. This world doesn't just have an atmosphere; it hides a massive, molten reservoir deep beneath its surface.

The exoplanet L 98-59 d orbits a small red star and presents a geological puzzle. While it is roughly 1.6 times the mass of Earth, it possesses an unusually low density for its size. Observations from the James Webb Space Telescope (JWST) revealed significant amounts of hydrogen sulfide in its atmosphere, a chemical fingerprint that didn't fit existing models of planetary composition.

By using advanced computer simulations to reconstruct nearly five billion years of the planet's history, researchers from the University of Oxford and other institutions identified a new category of world. The findings, published in Nature Astronomy, suggest the planet features a mantle of molten silicate—similar to Earth's lava—with a global magma ocean extending thousands of kilometers deep.

This vast molten reservoir allows the planet to store enormous amounts of sulfur over geologic timescales. This internal heat and liquid state also help L 98-59 d retain a thick, hydrogen-rich atmosphere containing sulfur-bearing gases like hydrogen sulfide. The discovery challenges current planetary science, proving that there are still unknown types of worlds waiting to be uncovered.

While this specific study focuses on molten planets, the broader field of exoplanetary research continues to expand our understanding of cosmic diversity. For instance, other systems like Beta Pictoris have revealed giant planets with orbits as wide as 30 astronomical units, further complicating our map of how planetary systems form and evolve.

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