TRAPPIST-1 c

Planet· orbits the Sun

TRAPPIST-1 c — the second planet, Earth-sized and rocky, on a 2.4-day orbit receiving about twice Earth's sunlight. JWST found no evidence of a thick carbon-dioxide atmosphere in 2023. Too hot for habitability; never imaged.

Open in 3D viewSee TRAPPIST-1 c in the live, interactive 3D map

Key facts

Mass

7.81 × 10²⁴ kg

1.31 M⊕

Radius

6,989 km

1.1× wider than Earth

Surface gravity

10.7 m/s²

1.09× Earth's

Year

2.42 Earth days

Distance from TRAPPIST-1

2,363,646 km

Science

Physical

Mass: 7.81 × 10²⁴ kg · 1.31 M⊕
Radius: 6,989 km · 1.1× wider than Earth
Density: 5,463 kg/m³ · 5.5× water
Surface gravity: 10.7 m/s² · 1.09× Earth's
Escape velocity: 12.2 km/s · 1.09× Earth's

Orbital

Semi-major axis: 2,363,646 km
Eccentricity: 0.00654
Inclination: 0.00 °
Orbital period: 2.4 days
Perihelion: 2,348,188 km
Aphelion: 2,379,105 km
Mean orbital velocity: 71 km/s

Atmosphere

Composition: In 2023 JWST thermal measurements found no sign of a thick, CO₂-rich atmosphere. Receiving about twice Earth's sunlight, it is too hot for habitability.

Composition

Bulk composition: Rocky. Mass 1.31 Earth and radius 1.10 Earth give an Earth-like density. Never imaged.
Surface appearance: Appearance based on NASA/ESA/CSA (JWST)'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: 2.22 S⊕ · 2.22× the sunlight Earth receives
Equilibrium temperature: 340 K (67 °C)

Discovery & history

Discovered: May 2, 2016
By: Michaël Gillon et al. (TRAPPIST / Spitzer)
Method: Transit detection
Name: Designated 'c' 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

TRAPPIST-1 c — artist concept accompanying JWST observations; not a photograph, its surface has never been imaged — NASA, ESA, CSA, J. Olmsted (STScI) (public domain) · Wikimedia Commons

TRAPPIST-1 c — NASA artist's concept; not a photograph, appearance unknown — NASA/JPL-Caltech (public domain) · Wikimedia Commons

Images from open archives · credit shown per image