# Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST

**Authors:** Thomas P. Greene, Taylor J. Bell, Elsa Ducrot, Achrène Dyrek, Pierre-Olivier Lagage, Jonathan J. Fortney  
**arXiv:** [2303.14849](https://arxiv.org/abs/2303.14849)  
**Date:** 2023-03-26  
**Summary page:** https://www.summarizepaper.com/en/paper/2303.14849v1/

## Key points

- The TRAPPIST-1 system has seven planets similar to those in our Solar System
- Transmission spectroscopy technique used with Hubble and Spitzer Space Telescopes, but no atmospheric features detected or strongly constrained
- TRAPPIST-1 b receives four times as much irradiation as Earth from the Sun
- Photometric secondary eclipse observations of TRAPPIST-1 b using F1500W filter of MIRI instrument on JWST were conducted by Thomas P. Greene and colleagues
- Secondary eclipse detected with 8.7-sigma confidence, suggesting only dayside hemisphere re-radiates incident flux from host star's radiation
- Little or no planetary atmosphere redistributing radiation from it or detectable atmospheric absorption from carbon dioxide (CO$_2$) or other species
- Findings provide important insights into planetary atmospheres and their evolution under extreme conditions like those found in close-in exoplanets like TRAPPIST-1 b

## Summary

The TRAPPIST-1 system consists of seven planets similar in size, mass, density and stellar heating to those found in our Solar System. It has been studied using the transmission spectroscopy technique with the Hubble and Spitzer Space Telescopes but no atmospheric features have been detected or strongly constrained. TRAPPIST-1 b is the closest planet to its M dwarf star and receives four times as much irradiation as Earth does from the Sun. This high level of stellar heating suggests that its thermal emission may be measurable. In this study Thomas P. Greene and colleagues present photometric secondary eclipse observations of TRAPPIST-1 b using the F1500W filter of the MIRI instrument on JWST. They detect a secondary eclipse with 8.7-sigma confidence when all data are combined which suggests that only the dayside hemisphere of the planet re-radiates incident flux from its host star's radiation and there is little or no planetary atmosphere redistributing radiation from it or detectable atmospheric absorption from carbon dioxide (CO$_2$) or other species. The authors conclude that their findings provide important insights into planetary atmospheres and their evolution under extreme conditions such as those found in close-in exoplanets like TRAPPIST-1 b.