Astronomers Identify Possible “Magma Ocean” Planet 35 Light Years Away
Astronomers studying a distant exoplanet say it may represent a previously unknown category of world—one dominated not by rock or water, but by molten lava.
The number of known exoplanets, or planets outside our solar system, has reached 6,000, according to NASA. The new research focuses on L98-59d, a planet orbiting a small red dwarf star roughly 35 light-years from Earth. The planet is about 1.6 times Earth’s size, placing it in a size range where scientists typically expect either rocky planets or ocean-covered “water worlds.” Yet new findings suggest it may instead be something entirely different.
Earlier observations using the James Webb Space Telescope revealed that L98-59d possesses an atmosphere unusually rich in sulfur. That chemical signature puzzled astronomers because neither rocky planets nor water worlds should be able to sustain such an atmosphere over the nearly 5 billion years the planet has existed.
To investigate, researchers at the University of Oxford ran advanced computer simulations tracing the planet’s evolution from shortly after its formation. The models suggest the world may contain a vast global magma ocean extending thousands of kilometers beneath its surface.
“Until now, astronomers would have placed a planet like this into one of two familiar categories, either a rocky ‘gas-dwarf’ with an atmosphere of hydrogen, or a water-rich world made of deep oceans and ice,” the University of Oxford said in a statement.
“These new findings reveal that L 98-59d fits neither description. Instead, it appears to belong to an entirely different class of planet containing heavy sulfur molecules.”
“You can only really explain this planet if it has this deep magma ocean inside of it,” said Dr. Harrison Nicholls, an astrophysicist at the university.
“The magma ocean efficiently stores the gases and keeps the gases protected from physical processes that would otherwise remove them.”
If the model is correct, L98-59d would be a world of extreme conditions. Scientists estimate that surface temperatures could reach 3,500°F (1,900°C). Tidal forces from neighboring planets may generate enormous waves across the molten surface, while the atmosphere, rich in hydrogen sulfide, would likely smell strongly of rotten eggs. “The whole thing really is in a mushy, molten state. It’s like molasses. It’s likely that this planet’s core would also be molten,” Nicholls said.
“We cannot yet quantify how rare this scenario is. However, given the results of our modeling, and also on the basis of well-justified physical processes which happen during planet formation, we believe that these magma ocean planets may represent a substantial fraction of the exoplanets in our galaxy.”
Although the discovery highlights the diversity of planetary systems beyond our own, researchers say the environment on L98-59d is unlikely to support life.
“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. It’s nice to revel in the alienness of the planet itself.”
Studying exoplanets has long posed challenges for astronomers. Because these worlds are too distant to visit or directly photograph, scientists historically relied on indirect measurements, such as monitoring the slight dimming of a star when a planet passes in front of it, to estimate properties like size, density and temperature.
More recently, the James Webb Space Telescope has enabled analysis of planetary atmospheres by examining how starlight filters through them. These observations provided the initial clues that L98-59d might not fit neatly into existing categories of planets.
The possibility that molten planets could exist in significant numbers may also complicate how astronomers evaluate distant worlds for potential habitability.
“Some planets in the so-called habitable zone might not be very habitable at all, they might be these molten planets,” Nicholls said.
“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 planets are waiting to be uncovered?”
Dr. Jo Barstow, a planetary scientist at the Open University who was involved in earlier Webb observations of L98-59d, said the new analysis offers a compelling explanation for the planet’s unusual characteristics.
“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.”
“What’s astonishing is that exoplanets are still delivering huge surprises decades after the field began,” said Dr. Sara Seager, an astrophysicist and planetary scientist at MIT, who wasn’t involved in the study. “We can look forward to more examples of this possible class of hydrogen-rich, sulfur-bearing atmosphere worlds.”
Moumita Basuroychowdhury is a Contributing Reporter at The National Digest. After earning an economics degree at Cornell University, she moved to NYC to pursue her MFA in creative writing. She enjoys reporting on science, business and culture news. You can reach her at moumita.b@thenationaldigest.com.
