Overview / Key Facts
- Distance: ~39 light-years from Earth
- Star Type: Ultracool M-dwarf
- Planets: Seven rocky, Earth-sized exoplanets (TRAPPIST-1b to TRAPPIST-1h)
- Orbital Periods: 1.5 to 18.8 days in the compact system
- Highlights: JWST breakthrough observations, atmospheric loss challenges, and habitability prospects for the exoplanets in this system
- Target Planets: Notably, TRAPPIST-1e, TRAPPIST-1f, and TRAPPIST-1g lie in the habitable zone
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Why TRAPPIST-1 Matters for Alien Life Research
This red dwarf system has transformed exoplanet science. This nearby ultracool dwarf, is about 39 light-years away, hosts seven rocky exoplanets. Among these, three of them orbit the habitable zone—where conditions might allow liquid water. With the powerful James Webb Space Telescope (JWST) focused on this system, scientists uncover secrets about these exoplanets’ atmospheres and surface conditions, deepening our understanding of habitability around M dwarfs like this Trappist system
Read more on this star system Here
Overcoming Stellar Interference: The Role of JWST
How Stellar Contamination Affects Data
Studying exoplanets is challenging because brightness variations from the star’s surface—such as spots and flares—can obscure a planet’s faint atmospheric signal. This stellar contamination makes it difficult to isolate the true signature of an exoplanet’s atmosphere.
Recent work by Rathcke et al. (2025) demonstrated that by observing consecutive transits of TRAPPIST-1b and TRAPPIST-1c, these effects can be reduced, making the data clearer and more reliable
Stellar Challenges: Active surface features on stars like red dwarfs significantly complicate exoplanet atmospheric studies.
Is TRAPPIST-1c Airless? New Insights from JWST
JWST’s NIRISS instrument has provided valuable insights into TRAPPIST-1c. In a study by Radica et al. (2025), two separate transits were analyzed after accounting for this star’s brightness variations. Their findings ruled out thick, hydrogen-rich atmospheres and dense water vapor, methane, or ammonia layers above about 10 mbar. For context, this planet’s dayside temperature is around 340 K—warmer than Earth’s average (288 K) but much cooler than Venus. These results suggest that the planet may be a bare rock or host only a very thin secondary atmosphere.
TRAPPIST-1b: Two Possible Scenarios
Observations using JWST/MIRI have led to two competing interpretations:
- Bare Rock Scenario:
- Planet might be a volcanic, ultramafic world—similar to Earth’s mantle rocks—with little to no atmosphere. The brightness temperatures (424 K at 12.8 µm and 478 K at 15 µm) support a scenario where intense stellar radiation has stripped the planet’s atmosphere.
- Hazy Atmosphere Scenario:
- Alternatively, it could possess a thick, CO₂-rich atmosphere with photochemical hazes, creating a thermal inversion. In this model, the upper atmosphere is hotter than the layers below, flipping absorption features into emission. However, strong UV radiation from a red dwarf would likely destroy methane, a key element in haze formation.
Bullet Points:
- Bare Rock: No detectable atmosphere; high reflectivity (Bond albedo ~0.19).
- Hazy Atmosphere: Potential CO₂-rich environment with a thermal inversion, though UV challenges methane’s survival.
Its temperature (478 K) is higher than Mercury’s dayside (~430 K), emphasizing the extreme conditions close to the star.
Or
TRAPPIST-1d: A Borderline World in the Habitable Zone
TRAPPIST-1d sits near the outer edge of the habitable zone. According to Way (2025), this exoplanet could fall into one of three categories:
- Exo-Venus: A planet with a runaway greenhouse effect and a thick CO₂ atmosphere.
- Exo-Earth: A world with moderate, life-sustaining conditions.
- Exo-Dead: A barren, airless world that has lost its atmosphere.
If TRAPPIST-1d has also experienced atmospheric erosion like its inner siblings, it reinforces the idea that even habitable-zone red dwarf exoplanets struggle to retain significant atmospheres.
Future Challenges in Detecting Exoplanet Atmospheres
Detecting the faint atmospheres of TRAPPIST-1 exoplanets remains a formidable task. Stellar flares and surface variations can create overlapping spectral signals—a phenomenon known as spectral degeneracy—where similar features may come from a hazy atmosphere or a bare rocky surface. Emission photometry, which measures a planet’s thermal glow during secondary eclipses, offers an alternative approach, yet it too faces these challenges. Future phase curve observations that track a planet’s emission over its orbit will be essential to disentangle these effects and reveal the true nature of these exoplanet atmospheres.
Conclusion: A Roadmap for Discovering Life Beyond Earth
The TRAPPIST-1 system remains a cornerstone in the search for extraterrestrial life. Its seven Earth-sized exoplanets, especially the potentially habitable TRAPPIST-1e, TRAPPIST-1f, and TRAPPIST-1g, offer a unique opportunity to understand the evolution of rocky worlds. Early JWST observations have revealed severe atmospheric challenges and stellar interference, yet future phase curve studies and advanced spectral models promise to clarify whether these planets can sustain life. As we continue to explore this system, the lessons learned will guide us in our broader quest to discover life beyond Earth.
References
- Carone, L., Barnes, R., Noack, L., Thamm, A., Bitsch, B., Barth, P., Garcia, R., Helling, C., Chubb, K., & Balduin, A. (2025). How to delay H₂O loss in the habitable zone of TRAPPIST: Add CO₂! Bulletin of the American Astronomical Society, 245th AAS Meeting, Vol. 57, No. 2, id. 172.02.
- Sintayehu, J., Barnes, R., & Driscoll, P. (2025). The Role of Magnetic Fields in Atmospheric Loss on TRAPPIST-1 Exoplanets e, f, and g. Bulletin of the American Astronomical Society, 245th AAS Meeting, Vol. 57, No. 2, id. 306.08.
- Radica, M., Piaulet-Ghorayeb, C., Taylor, J., Coulombe, L.-P., Benneke, B., & Albert, L. (2025). Promise and Peril: Stellar Contamination and Strict Limits on the Atmospheric Composition of TRAPPIST-1c from JWST NIRISS Transmission Spectra. The Astrophysical Journal Letters, 979(1), L5. https://iopscience.iop.org/article/10.3847/2041-8213/ad253f
- Peacock, S., Rustamkulov, Z., Moran, S., MacDonald, R., et al. (2025). JWST NIRSpec Observations of TRAPPIST-1h and b. Bulletin of the American Astronomical Society, 245th AAS Meeting, Vol. 57, No. 2, id. 232.03.
- Rathcke, A. D., Buchhave, L. A., De Wit, J., Rackham, B. V., August, P. C., et al. (2025). Stellar Contamination Correction Using Back-to-Back Transits of TRAPPIST-1b and c. The Astrophysical Journal Letters, 979(1), L19.
- Ducrot, E., Lagage, P.-O., Min, M., Gillon, M., Bell, T. J., Tremblin, P., et al. (2024). Combined Analysis of the 12.8 and 15 μm JWST/MIRI Eclipse Observations of TRAPPIST-1b. arXiv:2412.11627v1 [astro-ph.EP]. https://arxiv.org/abs/2412.11627
- Way, M. J. (2025). TRAPPIST-1d: Exo-Venus, Exo-Earth, or Exo-Dead? The Astrophysical Journal Letters, 980(1), L7. https://iopscience.iop.org/article/10.3847/2041-8213/ad2abc