Discovery of a Molten Lava Planet
Astronomers have identified a planet composed primarily of molten lava, indicating the possible existence of a new category of liquid planet.
The planet, designated L98-59d, is located approximately 35 light years from Earth and measures about 1.6 times the size of our planet. It orbits a small red star. Initial hypotheses suggested the planet might be similar to known types, but recent analyses indicate it could be fundamentally distinct from previously observed planets.
“The whole thing really is in a mushy, molten state,” said Dr Harrison Nicholls, an astrophysicist at the University of Oxford. “It’s like molasses. It’s likely that this planet’s core would also be molten.”
Surface temperatures on L98-59d are estimated to reach around 1,900°C (3,500°F). The planet is expected to have large waves traversing its magma ocean, driven by tidal forces from neighboring planets. Its atmosphere is rich in hydrogen sulphide, which would produce a pervasive odor reminiscent of rotten eggs. These extreme conditions are considered unfavorable for life as we know it.
“If there are aliens out there that could live in lava that would be amazing, but I don’t think it’s likely that it’s habitable,” said Nicholls. “It’s nice to revel in the alienness of the planet itself.”
Advances in Exoplanet Observation
Exoplanets such as L98-59d are too distant for direct imaging or robotic exploration. Historically, astronomers estimated their size, density, and temperature by observing the dimming of their host star’s light as the planet transited. The James Webb Space Telescope (JWST), however, enables more detailed study by analyzing starlight filtered through a planet’s atmosphere to identify its chemical composition.
Previous JWST observations revealed that L98-59d possesses a sulphur-rich atmosphere, which is inconsistent with it being either a rocky or water world—the two conventional categories for planets of its size. Neither type could sustain a sulphur-rich atmosphere over the nearly 5 billion years since the planet’s formation.
Simulations Reveal a Global Magma Ocean
Researchers employed advanced computer simulations to reconstruct L98-59d’s history from shortly after its formation to the present. These models suggest the planet harbors a global magma ocean extending thousands of kilometers beneath its surface, and possibly a molten core.
“You can only really explain this planet if it has this deep magma ocean inside of it,” said Nicholls. “The magma ocean efficiently stores the gases and keeps the gases protected from physical processes that would otherwise remove them.”
The findings imply that molten planets may be more common than previously thought and suggest caution when classifying exoplanets as potentially habitable.
“Some planets in the so-called habitable zone might not be very habitable at all, they might be these molten planets,” said Nicholls. “While this molten planet is unlikely to support life, it reflects the wide diversity of the worlds which exist beyond the solar system. We may then ask, what other types of planet are waiting to be uncovered?”
Expert Commentary
Dr Jo Barstow, a planetary scientist at the Open University who participated in the JWST observations of L98-59d, commented on the new findings.
“We talked about it possibly being an exoplanet that resembles Jupiter’s moon Io, with lots of volcanoes caused by tidal heating,” she said. “This work suggests it could be even more extreme.”
The research has been published in the journal .
