An international team of scientists has discovered possible traces of a sulfur-rich atmosphere on an exoplanet located 35 light-years from Earth.
This planet, named L 98-59 d, has a diameter one and a half times that of Earth and could be the smallest known exoplanet to possess an atmosphere.
The identified gases, including sulfur dioxide (SO₂) and hydrogen sulfide (H₂S), suggest the presence of a volcanic or molten surface.
In our Solar System, there are two main categories of planets: rocky bodies like Earth and Mars, and gas giants like Jupiter and Saturn.
However, exoplanets – planets that orbit other stars – offer a wider variety of sizes.
Many of these celestial bodies fall into an intermediate range between Earth and Neptune, a type absent in our system but very common in the galaxy.
Among these, the smaller planets are defined as super-Earths, while the larger ones are called sub-Neptunians.
L 98-59 d, classified as a super-Earth, was discovered in 2019 thanks to NASA’s TESS space telescope, using the transit method.
This approach measures the slight dips in starlight caused by the planet passing in front of its star, providing information about its size.
The atmosphere of L 98-59 d was analyzed through the James Webb Space Telescope (JWST), which observed the starlight filtered by the planet’s atmosphere during a transit. This light, analyzed through transmission spectroscopy, revealed clues of an unusual atmosphere rich in SO₂ and H₂S.
These gases are absent in the rocky planets of our system, where water vapor and carbon dioxide predominate.
The conditions of L 98-59 d could be extremely hostile, characterized by a volcanic or molten surface and high temperatures due to its proximity to its star, with a year lasting only seven Earth days.
Additionally, the possible presence of volcanic activity could be fueled by tidal heating, a phenomenon similar to that observed on Io, Jupiter’s moon.
The discovery of such a peculiar atmosphere represents an important breakthrough in the study of exoplanets.
Confirming the presence of these gases will require further observations with the JWST.
These data will not only allow a better understanding of the atmospheric composition of L 98-59 d but also deepen the evolutionary processes of planets outside our system.
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