TRAPPIST-1 d — day
Hypothetical warm humid terminator biosphere: tall hollow reed organisms, iridescent membrane gliders, long articulated limbs without vertebrate or human faces.
The imagined scene
The host system is real. All alien organisms, robots, societies and social histories are fictional. Moons, rings, terrain and weather are artistic assumptions unless specifically supported by a cited source. These images are not calibrated simulations of the sky.
The scientific anchor
This illustration is associated with TRAPPIST-1 d, a catalogued exoplanet orbiting TRAPPIST-1. The available catalog measurements below describe the real system; they do not establish the illustrated scenery.
Gillon et al. 2016 · Agol et al. 2021 · Grimm et al. 2018 · Ducrot et al. 2020 · Piaulet-Ghorayeb et al. 2025
Available measurements
Host: TRAPPIST-1 · 1 catalog star(s) · Rocky-size candidate
NASA composite catalog values may combine different papers. Errors and upper/lower limits are retained. “Calculated Value” means derived or estimated. Msini is a minimum mass. Missing values are unknown. A multiple-star system’s single stellar row does not describe every component. Equilibrium temperature is not a measured surface temperature.
| Quantity | Value & uncertainty | Unit | Paper / source |
|---|---|---|---|
| Planet radius | 0.788 [+0.011 / -0.01] | Earth radii | Agol et al. 2021 |
| Planet mass | 0.388 [+0.012 / -0.012] | Earth masses | Agol et al. 2021 |
| Bulk density | 4.3668 [+0.15438 / -0.16541] | g/cm³ | Agol et al. 2021 |
| Orbital period | 4.0492 [+2.6e-05 / -2.6e-05] | days | Agol et al. 2021 |
| Orbital semimajor axis | 0.02227 [+0.00019 / -0.00019] | AU | Agol et al. 2021 |
| Orbital eccentricity | 0.00837 [+0.00093 / -0.00093] | Grimm et al. 2018 | |
| Orbital inclination | 89.896 [+0.077 / -0.077] | degrees | Agol et al. 2021 |
| Irradiation | 1.115 [+0.043 / -0.043] | Earth flux | Agol et al. 2021 |
| Equilibrium temperature | 286.2 [+2.8 / -2.8] | K; not surface temperature | Ducrot et al. 2020 |
| Catalog stellar effective temperature | 2,566 [+26 / -26] | K | Agol et al. 2021 |
| Catalog stellar radius | 0.1192 [+0.0013 / -0.0013] | Solar radii | Agol et al. 2021 |
| Catalog stellar mass | 0.0898 [+0.0023 / -0.0023] | Solar masses | Agol et al. 2021 |
| Catalog stellar luminosity | -3.2573 [+0.01467 / -0.01518] | log10 Solar luminosity | Agol et al. 2021 |
| Catalog stellar age | 7.6 [+2.2 / -2.2] | Gyr | Piaulet-Ghorayeb et al. 2025 |
| Catalog stellar metallicity | 0.052 [+0.073 / -0.073] | dex | Piaulet-Ghorayeb et al. 2025 |
| System distance | 12.43 [+0.018707 / -0.018707] | pc | Gaia DR2 |
What about life?
Passes a deliberately broad 0.25–1.75 Earth-flux triage window. This is not a calculated habitable zone or evidence of water or life. Atmosphere, surface pressure, water inventory, stellar activity and orbital history remain unassessed. No confirmed life; no planet-specific biosignature literature review in this release.
Papers and references
Gillon et al. 2016 · Agol et al. 2021 · Grimm et al. 2018 · Ducrot et al. 2020 · Piaulet-Ghorayeb et al. 2025 · Gaia DR2