Recent measurements with the James Webb Space Telescope (JWST) cast doubt on the current understanding of the exoplanet Trappist-1 b's nature. Until now, it was assumed to be a dark rocky planet without an atmosphere, shaped by a billion-year-long cosmic impact of radiation and meteorites. The opposite appears to be true. The surface shows no signs of weathering, which could indicate geological activity such as volcanism and plate tectonics. Alternatively, a planet with a hazy atmosphere composed of carbon dioxide is also viable. The results demonstrate the challenges of determining the properties of exoplanets with thin atmospheres.
Trappist-1 b is one of seven rocky planets orbiting the star Trappist-1, located 40 light-years away. The planetary system is unique because it allows astronomers to study seven Earth-like planets from relatively close range, with three of them in the so-called habitable zone. This is the area in a planetary system where a planet could have liquid water on the surface. To date, ten research programmes have targeted this system with the James Webb Space Telescope (JWST) for 290 hours.
The current study, in which researchers from the Max Planck Institute for Astronomy (MPIA) in Heidelberg are significantly involved, was led by Elsa Ducrot from the Commissariat aux Énergies Atomiques (CEA) in Paris, France. This study uses measurements of the thermal infrared radiation -- essentially heat radiation -- of the planet Trappist-1 b with MIRI (Mid-Infrared Imager) at the JWST and has now been published in the journal Nature Astronomy. It includes the results from last year, on which the previous conclusions were based, which describe Trappist-1 b as a dark rocky planet without an atmosphere.
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