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Astronomers have spotted a planet orbiting a star in our neighborhood of the Milky Way galaxy that presents a unique hellscape \u2013 covered with a perpetual ocean of magma and \u200benveloped by a noxious and fiercely hot sulfur-rich atmosphere.<\/strong><\/p>\n The molten planet\u2019s diameter is more than 60% greater than Earth, though its density is only about \u200c40% that of our planet. It orbits a star smaller and dimmer than the sun located about 34 light-years from Earth in the constellation Volans. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).<\/p>\n \u201cThe planet lacks distinct structure within its magma ocean, so there is no crust, upper mantle and lower mantle. The magma ocean is a single deep, mushy layer,\u201d said Harrison Nicholls, a postdoctoral \u200bresearcher at the University of Cambridge Institute of Astronomy and lead author of the research published on Monday in the journal Nature Astronomy.<\/p>\n Small crystals of solid rock may be \u200btrapped within the turbulent fluid magma comprising the mantle, Nicholls said.<\/p>\n The planet\u2019s metallic core appears to be relatively small, with the magma ocean \u2060comprising 70-90% of the planetary interior radius \u2013 reaching a depth between 2,775 and 3,565 miles (4,465-5,740 km).<\/p>\n Its thick atmosphere is composed primarily of hydrogen, but has a very high sulfur content. \u200bAbout 10% of the atmosphere is the toxic gas hydrogen sulfide, which gives off the stench of rotten eggs. The atmosphere has caused a runaway greenhouse effect, trapping heat from the star, \u200bthat keeps the planet\u2019s surface so hot that it remains molten.<\/p>\n \u201cYour nose can smell hydrogen sulfide at concentrations of something like one part per billion, so this would be overwhelmingly stinky. But you wouldn\u2019t survive long enough in this hot atmosphere to notice,\u201d said planetary scientist and study co-author Raymond Pierrehumbert of the University of Oxford and Massachusetts Institute of Technology.<\/p>\n The atmosphere\u2019s composition suggests a high sulfur content in the planetary \u200binterior, the researchers said.<\/p>\n \u201cWe do not know the exact composition of the molten material but our interpretation of the observations suggests that the high sulfur content would likely mean a mineralogical \u200bcomposition different to our solar system\u2019s planets,\u201d Nicholls said.<\/p>\n The planet, named L 98-59 d, was discovered in 2019, then was observed by the James Webb Space Telescope in 2024 and by ground-based telescopes in \u200c2025. The \u2060researchers used advanced computer simulations to reconstruct its history spanning nearly five billion years, making it somewhat older than Earth.<\/p>\n It orbits a common type of star called a red dwarf. The star\u2019s mass is just under 30% that of the sun and its luminosity about 1% that of the sun. In terms of orbital distance, L 98-59 d is the third of five planets known to orbit this star.<\/p>\n More than 6,100 planets beyond our solar system, called exoplanets, have been discovered since the 1990s, though none quite like this one. Its unique combination of a \u200bmagma ocean and a sulfur-laden atmosphere puts it \u200bin a class by itself, for now.<\/p>\n Other \u2060molten planets are known, some orbiting so close to their host stars that their surfaces are broiled. That is not the dynamic with L 98-59 d.<\/p>\n \u201cA key point to recognize is that all planets \u2013 including Earth \u2013 start out molten, but this one has remained so because \u200bof a combination of factors,\u201d Nicholls said.<\/p>\n Its hot atmosphere plays the leading role in preventing the magma from hardening into rock, and \u200bits magma ocean helps maintain \u2060the harsh atmosphere. Two secondary factors in heating up L 98-59 d are the star\u2019s radiation and gravitational interactions with the system\u2019s other planets.<\/p>\n As scientists seek evidence of possible life on exoplanets, this one is not a promising candidate.<\/p>\n \u201cThis planet\u2019s surface is in excess of 1,500 degrees Celsius (2,732 degrees Fahrenheit), so it would not harbor life as we know it,\u201d Nicholls said.<\/p>\n \u201cThe era of exoplanet discovery \u2060keeps showing us \u200bnew kinds of worlds, indeed \u2018strange new worlds,\u2019 generally stranger than anything in \u2018Star Trek,’\u201d Pierrehumbert said, using a phrase \u200bfrom the \u201cStar Trek\u201d prologue. \u201cThis offers all sorts of exciting opportunities to put together fundamental physics in very novel ways.\u201d<\/p>\n<\/div>\n