An illustration of TRAPPIST-1b. Credits: NASA, ESA, CSA, J. Olmsted (STScI).

TRAPPIST-1 c’s Atmosphere is Thin, If Present, Reveals Webb

TRAPPIST-1 c is one of seven rocky planets orbiting an ultracool M dwarf star located 40 light-years from Earth.


Scientists across the globe have employed NASA’s James Webb Space Telescope, deducing a potentially negligible atmosphere surrounding the rocky exoplanet TRAPPIST-1 c, based on the recorded heat energy.

TRAPPIST-1 c’s Atmosphere is Thin If Present

The findings hint at a significantly thin, if not non-existent, atmosphere. The planet’s dayside temperature averages around 380 kelvins, or approximately 225 degrees Fahrenheit. This fact makes TRAPPIST-1 c the chilliest rocky exoplanet to have its thermal emission characterized.


The revelation enhances our understanding of rocky exoplanets similar to those in our solar system. It also contributes to the ongoing study of whether planets orbiting smaller red dwarfs, such as TRAPPIST-1, can harbor life-supporting atmospheres.

Unraveling the Exoplanetary Atmospheres

“Previously, we could only scrutinize planets with dense hydrogen-rich atmospheres,” said first author Sebastian Zieba. “With Webb, we can now probe for atmospheres dominated by elements such as oxygen, nitrogen, and carbon dioxide.”

The researchers viewed TRAPPIST-1 c, a planet comparable in size to Venus, as potentially having a thick CO2 atmosphere, much like Venus itself.

The Puzzling Nature of TRAPPIST-1 c

TRAPPIST-1 c is one of seven rocky planets orbiting an ultracool M dwarf star located 40 light-years from Earth. The planets, comparable in size and mass to Earth’s inner planets, have atmospheres that remain enigmatic.


M dwarfs are known for intense X-ray and ultraviolet radiation early in their lives, which can erode a young planetary atmosphere. Moreover, the availability of crucial elements such as water, CO2, and other volatiles during their formation remains uncertain.

Finding Clues in Light Patterns

The scientists utilized MIRI, Webb’s Mid-Infrared Instrument, to observe the TRAPPIST-1 system. They monitored the planetary system during secondary eclipse events, comparing brightness levels to calculate the amount of mid-infrared light emitted by the planet’s dayside.

An Insight into the Planetary Atmosphere

The planet’s infrared light emission, affected by its temperature and atmospheric composition, provided valuable insights. A thick CO2 atmosphere would absorb 15-micron light, causing the planet to appear dimmer at that wavelength. Conversely, atmospheric clouds would reflect light, making the planet seem brighter and obscuring the presence of CO2.

Gleaning Information on TRAPPIST-1 c

“Our findings align with a scenario where the planet lacks an atmosphere or has an extremely thin CO2 atmosphere, sans clouds,” stated Zieba. “If the planet had a dense CO2 atmosphere, we would have observed an exceptionally shallow secondary eclipse or none.”

The data dismisses the likelihood of the planet being a true Venus analog with a dense CO2 atmosphere and sulfuric acid clouds. This suggests the planet might have formed with limited water, potentially applicable to other cooler planets in the TRAPPIST-1 system.


A New Dawn in Exoplanet Study

This high-precision investigation showcases the extraordinary capability of the Webb telescope. “Webb brings us to a point where we can compare exoplanet systems to our solar system like never before,” asserted Laura Kreidberg, a co-author of the study.

This study lays the groundwork for further research, including full-orbit observations of TRAPPIST-1 b and c, enhancing our understanding of these mysterious celestial bodies.

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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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