TRAPPIST-1 h
Astrophysical Synthesis & Habitability Characterization
TRAPPIST-1 h is a confirmed sub-earth 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 0.3372% across the stellar disk), this world measures 0.755 Earth radii and has a measured mass of 0.326 Earth masses. Combining its mass and radius yields a mean bulk density of 4.18 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.57 g⊕ (5.59 m/s²), and an escape velocity of 7.4 km/s.
In its orbital architecture around TRAPPIST-1, TRAPPIST-1 h completes one full revolution every 18.773 Earth days at a semi-major axis of 0.06189 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 35.9 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.00567 (ranging from 0.0615 AU at periapsis to 0.0622 AU at apoapsis), the planet experiences minimal orbital distance variation.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 172 K (-101°C / -150°F) and an incident flux of 0.14 S⊕ (~196 W/m²), surface water and volatile species on TRAPPIST-1 h would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
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 h sharing its stellar neighborhood alongside TRAPPIST-1 b, TRAPPIST-1 c, TRAPPIST-1 d, TRAPPIST-1 e, TRAPPIST-1 f, TRAPPIST-1 g.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | TRAPPIST-1 |
| Spectral Type | M8.0 V |
| Effective Temp (Teff) | 2,566 K |
| Stellar Radius | 0.1192 R☉ |
| Stellar Mass | 0.0898 M☉ |
| Bolometric Luminosity | 0.00055 L☉ |
| Metallicity [Fe/H] | 0.052 dex |
| Stellar Age | 7.600 Gyr |
| Apparent Magnitude | V: 17.020 · G: 15.645 |
| System Architecture | 1 Star, 7 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.061890 AU |
| Orbital Period | 18.773 days |
| Mean Orbital Velocity | 35.9 km/s |
| Orbital Eccentricity (e) | 0.00567 |
| Orbital Inclination (i) | 89.8050° |
| Mean Bulk Density | 4.18 g/cm³ (7.4 km/s vesc) |
| Insolation Flux | 0.1440 S⊕ (~196 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 40.500 LY (12.430 pc) |