TRAPPIST-1 e
Planet· orbits TRAPPIST-1
TRAPPIST-1 e — an Earth-sized, rocky planet in the middle of the habitable zone, receiving about 65% of Earth's sunlight. Its measured mass and radius give a near-Earth density, making it the most Earth-like of the seven in size and composition. Potentially habitable — but no atmosphere, water or surface has been detected, and its appearance is unknown.
Open in 3D viewSee TRAPPIST-1 e in the live, interactive 3D map
Key facts
Mass
4.13 × 10²⁴ kg
0.692 M⊕
Radius
5,861 km
92% of Earth's radius
Surface gravity
8.03 m/s²
82% of Earth's gravity
Year
6.1 Earth days
Distance from TRAPPIST-1
4,375,738 km
Science
Physical
- Mass
- 4.13 × 10²⁴ kg · 0.692 M⊕
- Agol et al. 2021 — transit-timing variations
- Radius
- 5,861 km · 92% of Earth's radius
- Agol et al. 2021 — transit photometry
- Density
- 4,900 kg/m³ · 4.9× water
- Computed from mass and radius
- Surface gravity
- 8.03 m/s² · 82% of Earth's gravity
- Computed from mass and radius
- Escape velocity
- 9.7 km/s · 87% of Earth's escape velocity
- Computed from mass and radius
Orbital
- Semi-major axis
- 4,375,738 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
- 0.0051
- 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
- 6.1 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
- 4,353,421 km
- Computed from the orbital elements
- Aphelion
- 4,398,054 km
- Computed from the orbital elements
- Mean orbital velocity
- 52.2 km/s
- Computed from the orbital elements
Atmosphere
- Composition
- Unknown — no atmosphere has been detected or ruled out. TRAPPIST-1 e sits squarely in the habitable zone and receives about 65% of Earth's sunlight, so with a suitable atmosphere it could hold liquid water — but it is likely tidally locked and exposed to the star's flares, and whether it keeps any atmosphere is unknown. 'Potentially habitable' is a statement about starlight, not a finding of habitability.
Composition
- Bulk composition
- Rocky. Its measured mass (0.69 Earth) and radius (0.92 Earth) give a near-Earth density, consistent with a rock-and-iron world — in size and composition the most Earth-like of the seven. Nothing of its surface has ever been imaged; its appearance is 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
- 0.646 S⊕ · 65% of the sunlight Earth receives
- Computed from TRAPPIST-1's luminosity and the orbital distance (inverse-square; Earth's sunlight = 1).
- Equilibrium temperature
- 250 K (-23 °C)
- Computed model value (assumes no atmosphere), for the ~65% of Earth's flux the planet receives — not a measured temperature. The real surface temperature depends on an atmosphere that has not been detected.
Discovery & history
- Discovered
- February 22, 2017
- By
- Michaël Gillon et al. (TRAPPIST / Spitzer)
- Method
- Transit detection
- Name
- Designated 'e' 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