James Webb Telescope Observations Rule Out Dense Atmospheres on Inner TRAPPIST-1 Rocky Exoplanets

New JWST findings show TRAPPIST-1b and TRAPPIST-1c lack atmospheres, with 500-degree temperature gaps. Discover what this means for exoplanet habitability.

By: AXL Media

Published: Apr 13, 2026, 7:58 AM EDT

Source: Information for this report was sourced from Université de Genève

The Thermal Mapping of Earth-Sized Celestial Neighbors

An international research initiative utilizing the James Webb Space Telescope has achieved a significant milestone in exoplanetary science by documenting the climatic conditions of distant rocky worlds. By focusing on the TRAPPIST-1 system, a cluster of seven planets orbiting a red dwarf star, scientists from the University of Geneva and the University of Bern have moved beyond simple detection to active climate mapping. The study centered on the two innermost planets, TRAPPIST-1b and TRAPPIST-1c, which serve as critical test cases for understanding how Earth-like planets evolve in high-radiation environments. According to the research published in Nature Astronomy, these observations represent the first time the surface temperatures of such small, rocky exoplanets have been measured with this level of precision.

The Harsh Realities of Red Dwarf Star Proximity

While red dwarfs are the most common stars in the Milky Way, their habitability remains a subject of intense debate due to their volatile nature. These stars are known to emit powerful ultraviolet radiation and particle fluxes that can strip away planetary gases over time. The two studied planets orbit their host star at such close range that they have become tidally locked, meaning one hemisphere faces the star in perpetual daylight while the other remains in a state of eternal night. Brice-Oliver Demory of the University of Bern explains that a dense atmosphere would typically act as a heat engine, moving energy from the scorching day side to the frigid night side. However, the lack of such heat transfer suggests that the stellar bombardment has effectively eroded any gaseous envelope these worlds might have once possessed.

Quantifying the Extreme Temperature Divide

The research team dedicated 60 hours of observation time to tracking the infrared light flux of the two inner planets throughout their orbits. The resulting data showed a staggering contrast between the two hemispheres, with daytime temperatures on the surface reaching between 100°C and 200°C. In contrast, the night sides of these planets were found to be plunged into extreme cold, dropping below -200°C. This 500-degree differential provides clear evidence that there is no energy redistribution taking place, confirming the absence of a substantial atmosphere. The data suggests th...