TRAPPIST-1 h
Planet· orbits TRAPPIST-1
TRAPPIST-1 h — the outermost and coldest planet, small (0.76 Earth radii) and on a 19-day orbit receiving only ~14% of Earth's sunlight. Its low density suggests an icy, volatile-rich make-up. Beyond the habitable zone and too cold for liquid water without a powerful atmosphere; never imaged.
Open in 3D viewSee TRAPPIST-1 h in the live, interactive 3D map
Key facts
Mass
1.95 × 10²⁴ kg
0.326 M⊕
Radius
4,810 km
76% of Earth's radius
Surface gravity
5.62 m/s²
57% of Earth's gravity
Year
18.77 Earth days
Distance from TRAPPIST-1
9,258,612 km
Science
Physical
- Mass
- 1.95 × 10²⁴ kg · 0.326 M⊕
- Agol et al. 2021 — transit-timing variations
- Radius
- 4,810 km · 76% of Earth's radius
- Agol et al. 2021 — transit photometry
- Density
- 4,176 kg/m³ · 4.2× water
- Computed from mass and radius
- Surface gravity
- 5.62 m/s² · 57% of Earth's gravity
- Computed from mass and radius
- Escape velocity
- 7.35 km/s · 66% of Earth's escape velocity
- Computed from mass and radius
Orbital
- Semi-major axis
- 9,258,612 km
- Real orbital elements (semi-major axis, period, eccentricity) from the NASA Exoplanet Archive; the system is shown face-on in the zone plane
- Eccentricity
- 0.00567
- Real orbital elements (semi-major axis, period, eccentricity) from the NASA Exoplanet Archive; the system is shown face-on in the zone plane
- Inclination
- 0.00 °
- Real orbital elements (semi-major axis, period, eccentricity) from the NASA Exoplanet Archive; the system is shown face-on in the zone plane
- Orbital period
- 18.8 days
- Real orbital elements (semi-major axis, period, eccentricity) from the NASA Exoplanet Archive; the system is shown face-on in the zone plane
- Perihelion
- 9,206,116 km
- Computed from the orbital elements
- Aphelion
- 9,311,109 km
- Computed from the orbital elements
- Mean orbital velocity
- 35.9 km/s
- Computed from the orbital elements
Atmosphere
- Composition
- Unknown. Beyond the habitable zone and receiving only ~14% of Earth's sunlight, TRAPPIST-1 h is too cold for liquid water without a powerful atmosphere; none has been detected.
Composition
- Bulk composition
- Small (0.76 Earth radii) and the least dense of the seven, suggesting an icy, volatile-rich make-up. Never imaged; appearance unknown.
- 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 Visual mode; Realism shows a plain spectral colour.
Radiation & temperature
- Insolation
- 0.144 S⊕ · 14% of the sunlight Earth receives
- Computed from TRAPPIST-1's luminosity and the orbital distance (inverse-square; Earth's sunlight = 1).
- Equilibrium temperature
- 172 K (-101 °C)
- Computed model value (assumes no atmosphere), for the ~14% of Earth's flux the planet receives on its 19-day orbit — not measured.
Discovery & history
- Discovered
- February 22, 2017
- By
- Michaël Gillon et al. (TRAPPIST / Spitzer)
- Method
- Transit detection
- Name
- Designated 'h' 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.
Revealed in February 2017, when a 20-day campaign by NASA's Spitzer Space Telescope with ground-based telescopes showed TRAPPIST-1 hosts seven transiting planets (Gillon et al., Nature, 2017). Its mass was later measured from the tiny timing tugs the planets exert on one another (transit-timing variations).
Images
Images from open archives · credit shown per image