Recent findings on L 98-59d, part of the five-planet system L 98-59, indicate that this intriguing exoplanet may host an extensive global magma ocean, effectively trapping sulfur deep within its interior. This discovery introduces a previously unidentified category of extraterrestrial worlds.
The distant L 98-59 system lies approximately 34.5 light-years away in the southern constellation Bootes.
Known as TOI-175 or TIC 307210830, this bright M dwarf star has a mass roughly one-third that of the Sun.
This intriguing planetary system features at least three transiting planets and two non-transiting planets: L 98-59b, L 98-59c, L 98-59d, L 98-59e, and L 98-59f.
L 98-59d completes an orbit around its parent star every 7.5 days and is about 1.6 times larger than Earth, receiving approximately four times the radiant energy of our planet.
A recent study led by astronomer Harrison Nichols from the University of Oxford aimed to reconstruct the planetary history of this super-Earth, tracing its evolution from its formation nearly 5 billion years ago.
By correlating telescope observations with comprehensive physical models of the planet’s interior and atmosphere, the research team gained insights into the planet’s deep geological processes.
The findings suggest that L 98-59d possesses a mantle of molten silicate similar to Earth’s lava, underpinned by a vast global magma ocean that extends for thousands of kilometers.
This massive molten reservoir enables L 98-59d to store significant amounts of sulfur within its interior over geological timescales.
Moreover, the magma ocean assists in retaining a hydrogen-rich atmosphere laden with sulfur compounds like hydrogen sulfide, which is typically lost to space due to X-ray radiation emitted by the host star.
Over billions of years, the interplay between its molten interior and atmosphere has sculpted L 98-59d into the striking world observed today.
Researchers propose that L 98-59d may represent the inaugural example of a newly identified category of gas-rich sulfur exoplanets that sustain long-lived magma oceans. If validated, this could greatly expand our understanding of planetary diversity in the galaxy.
“This discovery highlights that the current classifications of small planets may be overly simplistic,” remarked Dr. Nichols.
“While this molten world is unlikely to support life, it showcases the vast array of planets beyond our solar system. What other types of celestial bodies remain undiscovered?”
For more details, refer to the study published in today’s edition of Nature Astronomy.
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H. Nichols et al. Evolution of a volatile-rich molten super-Earth L 98-59d. Nat Astron, published online March 16, 2026. doi: 10.1038/s41550-026-02815-8
Source: www.sci.news
