TRAPPIST-1 Archives

Illustration of flare heating in three types of stars. The dashed line marks the stellar surface; blue areas show the quiet atmosphere, and red areas show regions heated during a white-light flare. Vertical arrows indicate the radiative output, with length proportional to intensity. In solar-like stars (left), heating is regulated by hydrogen ionization, which limits temperatures of white-light flares to ∼ 9000 K. In late M dwarfs like TRAPPIST-1 (middle), molecular hydrogen dissociation acts as a thermostat, capping temperatures of white-light flares near ∼ 3500 − 4000 K. In early M dwarfs (right), insufficient concentration of H2 means the dissociation thermostat is ineffective, allowing higher white-light flare temperatures. -- astro-ph.SR

Exoplanets, -moons, -comets, Radiation, Space Weather & Heliophysics, Status Report, TRAPPIST-1

Molecular Hydrogen Controls The Temperatures Of Flares On TRAPPIST-1

by Keith CowingJanuary 6, 2026January 6, 2026

Early JWST observations of TRAPPIST-1 have revealed an unexpected puzzle: energetic white-light flares (E>1030 erg) reach temperatures of only ∼3500–4000,K, nearly three times cooler than typical solar flares, which peak […]

Final semi-major axes of satellites versus their initial orbital distance (in Hill radii) for TRAPPIST-1 e. -- astro-ph.EP

Exoplanets, -moons, -comets, Status Report, TRAPPIST-1

Orbital Stability Of Moons Around The TRAPPIST-1 Planets

by Keith CowingDecember 23, 2025December 23, 2025

We investigate the dynamical stability of potential satellites orbiting the seven planets of the TRAPPIST-1 system using a suite of N-body simulations.

Top: White light curves of observation 1, observation 3, and observation 15 from the NA reduction, both at native time resolution in black and binned to 25x in red for visibility. All transits are labeled by planet. Observation 1 also has a large flare that occurs right before the egress of planet e. Shown in the upper right is a schematic of our proposed setup, with the true overlapping planetary transit chords taken from Agol et al. (2021). Middle: Hα light curve from the NA reduction. Peaks in Hα correspond to flaring events, many of which are not visible in the white light curve, at least without hints to their location from the Hα signature. Note that the light curves are binned in time to 50x (to approximately 70 second bins) relative to that shown in the white light curve for visibility in the low signal single wavelengths shown. Bottom: Transmission spectrum of TRAPPIST-1 e (top) and TRAPPIST-1 b (bottom) for observation 1, observation 3, and observation 15 from left to right. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report, TRAPPIST-1

JWST TRAPPIST-1 e/b Program: Motivation and First Observations

by Keith CowingDecember 9, 2025December 9, 2025

One of the forefront goals in the field of exoplanets is the detection of an atmosphere on a temperate terrestrial exoplanet, and among the best suited systems to do so […]

Located about 39 light-years from Earth, the TRAPPIST system resembles a miniature version of our solar system: The star, an ultracool red dwarf, and all its planets would comfortably fit inside the orbit of planet Mercury. Credit NASA, ESA, CSA, STScI, Joseph Olmsted (STScI)

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Press Release, Titan, TRAPPIST-1

A New Look At TRAPPIST-1e, An Earth-sized, Habitable-zone Exoplanet

by Keith CowingDecember 5, 2025December 5, 2025

Of the seven Earth-sized worlds orbiting the red dwarf star TRAPPIST-1, one planet in particular has attracted the attention of scientists, because it orbits the star within the “Goldilocks zone” […]

Overview of the atmosphere-interior exchange model we use for this study including the various geological processes that we simulate and the various parameters we consider in this model. The carbon cycle is the major overarching process added to this model, which is a negative feedback cycle that regulates the temperature of the planet over geologic timescales, which is crucial for studying habitability. -- astro-ph.EP

Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, TRAPPIST-1

The Effect of Oxygen Fugacity and Initial Volatile Abundance on the Atmospheres of the TRAPPIST-1 Planets

by Keith CowingNovember 17, 2025November 17, 2025

The TRAPPIST-1 planets have become prime targets for studying the atmospheric and geophysical properties of planets around M-dwarf stars.

Core–mantle partition coefficient of oxygen as a function of pressure and temperature. Left: Experimental data for metal–silicate partitioning of O obtained at high pressures up to 104 GPa. Horizontal dashed line located at DO=0.83 indicates full oxidation of the core (see the main text), and therefore distinguishes ‘terrestrial’ from ‘coreless’ planets. It is clear that, within the investigated pressure range, DO asymptotically approaches the dashed line, but never reaches the core-free regime, albeit higher pressures and temperatures promote the sequestration of O into the metallic core, i.e. larger DO. Right: The same dataset for O partitioning plotted as a function of reciprocal temperature. Dashed lines are fitted results (Eq. 7) showing the dependence of O partitioning on temperature at a given pressure or vice versa. -- astro-ph.EP

Astrogeology, Exoplanets, -moons, -comets, Status Report, TRAPPIST-1

Limits On Forming Coreless Terrestrial Worlds In The TRAPPIST-1 System

by Keith CowingNovember 4, 2025November 4, 2025

With seven temperate Earth-sized planets revolving around an ultracool red dwarf, the nearby TRAPPIST-1 system offers a unique opportunity to verify models of exoplanet composition, differentiation, and interior structure.

Contour plots of surface temperature, cloud water column, albedo, and OLR for our four representative climate states. -- Planetary Science Journal

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report, TRAPPIST-1

Chemistry, Climate, And Transmission Spectra Of TRAPPIST-1 e Explored With A Multimodel Sparse Sampled Ensemble

by Keith CowingOctober 16, 2025October 16, 2025

TRAPPIST-1 e is one of a few habitable zone exoplanets that is amenable to characterization in the near term. In this study our motivations are both scientific and technical.

Snapshots of VGS-calculated surface water mass (in units of Earth’s ocean mass) for TRAPPIST-1 analogs, shown as a function of total planet mass (M⊕) and final orbital distance (AU). Panel (a) depict planets at the halfway point of accretion (i.e., when the protoplanet reaches half its final mass), while panels (b) show the final planet properties. Measured properties of the TRAPPIST-1 planets are indicated by black circles (Agol et al. 2021). At mid-assembly, most inner planets are water-poor due to early impact-driven loss and higher irradiation. By the end of accretion, increased volatile delivery events from more water-rich materials and reduced erosion allow many planets, particularly beyond ∼0.03 AU,to accumulate and preserve large water reservoirs, leading to the strong radial gradient in water content. -- astro-ph.EP

Analog Studies, Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Status Report, TRAPPIST-1, Water/Hycean Worlds & Oceanography

Born Dry or Born Wet? A Palette of Water Growth Histories in TRAPPIST-1 Analogs and Compact Planetary Systems

by Keith CowingOctober 15, 2025October 15, 2025

It is still unclear whether exoplanets in compact multiplanet systems such as TRAPPIST-1 are able to accrete large quantities of volatiles, grow to sufficient mass, and maintain robust atmospheres and […]

JWST NIRSpec PRISM transmission spectra compared with modeled atmospheric scenarios. The x-axis shows wavelengths in microns, while the y-axis shows the transit depth in parts per million. Each of the individual visits (translucent colored circles with error bars), the combination of visits 1 and 2 (gray circles with error bars), and the stellar-contamination-corrected four-visit spectrum from N. Espinoza et al. (2025; black circles with error bars) are compared to the HST data from J. de Wit et al. (2018; dark red stars with error bars). An array of forward-model spectra for different atmospheric scenarios is overlaid (colored lines). Atmospheric models rich in H2 can be easily ruled out, while many high mean molecular weight scenarios are consistent with the JWST data. -- IOPscience

Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Extremeophiles and Extreme Environments, Habitable Zones, Imaging & Spectroscopy, Status Report, TRAPPIST-1

JWST-TST DREAMS: Secondary Atmosphere Constraints for the Habitable Zone Planet TRAPPIST-1 e

by Keith CowingOctober 14, 2025October 14, 2025

The TRAPPIST-1 system offers one of the best opportunities to characterize temperate terrestrial planets beyond our own solar system.

H2 abundance constraints for TRAPPIST-1 e from HST and JWST as a function of surface pressure. Posterior distribution showcasing the improvement on constraints on possible H2-dominated atmospheres on TRAPPIST-1 e between HST (left in gray; obtained by applying our GP retrieval methodology to the HST/WFC3 data in Z. Zhang et al. 2018) and JWST (right in blue; obtained by applying it to the four NIRSpec/PRISM transits presented in this work). The distribution for HST mainly follows the centered log-ratio prior allowing the H2-dominated solution at virtually all pressures ≳1 bar; the JWST one disfavors the H2-dominated solution. -- IOPscience

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report, TRAPPIST-1

JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e

by Keith CowingOctober 14, 2025October 14, 2025

TRAPPIST-1 e is one of the very few rocky exoplanets that is both amenable to atmospheric characterization and resides in the habitable zone of its star—located at a distance from […]