TRAPPIST-1 g

Astrophysical Synthesis & Habitability Characterization

TRAPPIST-1 g is a confirmed terrestrial exoplanet orbiting the star TRAPPIST-1, located approximately 40.5 light-years (12.43 parsecs) from the Solar System. First announced in 2017 by Multiple Observatories using the Transit detection technique (producing an estimated primary transit depth of 0.754% across the stellar disk), this world measures 1.129 Earth radii and has a measured mass of 1.321 Earth masses. Combining its mass and radius yields a mean bulk density of 5.06 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.04 g⊕ (10.2 m/s²), and an escape velocity of 12.1 km/s.

In its orbital architecture around TRAPPIST-1, TRAPPIST-1 g completes one full revolution every 12.352 Earth days at a semi-major axis of 0.04683 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 41.2 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.00208 (ranging from 0.0467 AU at periapsis to 0.0469 AU at apoapsis), the planet experiences minimal orbital distance variation.

✓ Classified as a Temperate Habitable Zone Candidate.

With an estimated equilibrium temperature of 197 K (-76°C / -105°F) and an incident stellar irradiance of 0.25 S⊕ (~343 W/m²), TRAPPIST-1 g orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.

The host star TRAPPIST-1 is classified as a low-mass red dwarf of spectral type M8.0 V with an effective photospheric temperature of 2,566 K, a radius of 0.1192 R☉, a mass of 0.0898 M☉, an estimated bolometric luminosity of 0.00055 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.6 Gyr and a metallicity of [Fe/H] = 0.052 dex (metal-rich relative to the Sun). From Earth, TRAPPIST-1 shines at apparent V-band magnitude 17.02 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TRAPPIST-1 system is a multi-planet architecture hosting 7 confirmed worlds, with TRAPPIST-1 g sharing its stellar neighborhood alongside TRAPPIST-1 b, TRAPPIST-1 c, TRAPPIST-1 d, TRAPPIST-1 e, TRAPPIST-1 f, TRAPPIST-1 h.

Discovery Facility: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).