1 / 5 | The strange planet discovered by scientists that has a magma ocean. SMACS 0723 | NASA’s James Webb Space Telescope produced the deepest, sharpest infrared image of the distant universe to date. Known as “Webb’s First Deep Field,” this image of the galaxy cluster SMACS 0723 is packed with detail. -Twitter
An international team of scientists, led by the University of Oxford (United Kingdom), has identified a new class of planet outside the Solar System that does not fit into any of the categories known until now, characterized by hosting enormous amounts of sulfur in the depths of a permanent ocean of magma.
The planet, called “L 98-59 d”, orbits a star located about 35 light years from Earth; It has a surprisingly low density and an atmosphere rich in sulfur gases, which initially baffled astronomers, who today published the results of their research in the journal Nature Astronomy.
The discovery of the new planet, which is 1.6 times the size of Earth, could significantly expand what is known so far about the diversity of worlds in the galaxy, stressed the researchers, who have used observations made with the James Webb space telescope, together with ground-based observatories, to reveal the presence of hydrogen sulfide and other sulfur compounds in the planet’s atmosphere.
A new category of worlds
These features don’t fit the usual categories into which small planets are classified, such as rocky gas dwarfs with hydrogen atmospheres or water-rich worlds made up of deep oceans and ice, and to understand this strange world, researchers used advanced computer simulations that recreate the planet’s evolution over almost five billion years.
Models suggest that the planet’s mantle is made up primarily of molten silicates, similar to Earth’s lava, creating a global ocean of magma that could extend thousands of kilometers beneath its surface, and that gigantic molten reservoir acts as a sulfur storehouse, capable of holding it over geological time scales.
In addition, this magma ocean contributes to maintaining a dense atmosphere rich in hydrogen, where gases such as hydrogen sulfide are found, and although normally this gas would be lost to space due to radiation from the host star, the chemical exchange between the molten interior and the atmosphere has allowed it to be preserved for billions of years.
The lead author of the study, Harrison Nicholls, explained that the discovery could force us to rethink the current categories with which astronomers have described small planets, and explained that although it is unlikely that a molten planet like this could support life, its study reveals the enormous diversity of worlds that exist outside the Solar System and raises the possibility that there are many more similar planets yet to be discovered.
How are they formed and which ones could be habitable?
Observations made in 2024 with the James Webb Space Telescope detected sulfur dioxide in the upper layers of the planet’s atmosphere, and models indicate that these gases are generated when ultraviolet radiation from its star triggers chemical reactions in the atmosphere.
At the same time, the magma ocean beneath the surface acts as a gigantic reservoir that absorbs and releases these compounds over time, and this interaction between the interior of the planet and its atmosphere is what would explain the unusual properties detected by the telescopes.
The space telescope thus continues to provide key information on exoplanets, and future space missions, such as Ariel and PLATO – both from ESA, to study hundreds of exoplanets – could further expand this knowledge and better understand how they form and evolve and predict which ones could be habitable.