TRAPPIST-1 d
Planet· orbits the Sun
TRAPPIST-1 d — a smaller planet (0.79 Earth radii) on a 4-day orbit at the hot inner edge of the habitable zone, receiving slightly more sunlight than Earth. Its lower density hints at a larger water or volatile fraction. Whether it holds an atmosphere is unknown; its surface has never been imaged.
Open in 3D viewSee TRAPPIST-1 d in the live, interactive 3D map
Key facts
Mass
2.32 × 10²⁴ kg
0.388 M⊕
Radius
5,020 km
79% of Earth's radius
Surface gravity
6.14 m/s²
63% of Earth's
Year
4.05 Earth days
Distance from TRAPPIST-1
3,331,545 km
Science
Physical
- Mass
- 2.32 × 10²⁴ kg · 0.388 M⊕
- Radius
- 5,020 km · 79% of Earth's radius
- Density
- 4,372 kg/m³ · 4.4× water
- Surface gravity
- 6.14 m/s² · 63% of Earth's
- Escape velocity
- 7.85 km/s · 70% of Earth's
Orbital
- Semi-major axis
- 3,331,545 km
- Eccentricity
- 0.00837
- Inclination
- 0.00 °
- Orbital period
- 4.0 days
- Perihelion
- 3,303,660 km
- Aphelion
- 3,359,430 km
- Mean orbital velocity
- 59.8 km/s
Atmosphere
- Composition
- Unknown — none detected or ruled out. TRAPPIST-1 d sits at the hot inner edge of the habitable zone, receiving slightly more sunlight than Earth; whether it holds an atmosphere is unknown.
Composition
- Bulk composition
- Rocky, but its lower density hints at a larger water or volatile fraction than the inner pair. Its true make-up and appearance are unknown — never imaged.
- Surface appearance
- Appearance based on NASA/JPL-Caltech's artist's concept. No spacecraft has imaged this world, so its real appearance is unknown — The surface shown is an artistic representation, shown only in Vision mode; Realism shows a plain spectral colour.
Radiation & temperature
- Insolation
- 1.12 S⊕ · 1.12× the sunlight Earth receives
- Equilibrium temperature
- 286 K (13 °C)
Discovery & history
- Discovered
- May 2, 2016
- By
- Michaël Gillon et al. (TRAPPIST / Spitzer)
- Method
- Transit detection
- Name
- Designated 'd' by its position in the system — planets are lettered inward to outward starting at 'b', so TRAPPIST-1 b is the innermost and h the outermost.
First detected in 2016 with the TRAPPIST telescope at ESO's La Silla Observatory (Gillon et al., Nature, May 2016) — among the first planets found transiting an ultracool dwarf star. Its size and orbit were pinned down the following year by NASA's Spitzer Space Telescope, which revealed the full seven-planet system.
Images
Images from open archives · credit shown per image