TRAPPIST-1 g
Reference profile for TRAPPIST-1 g: 1.129 Earth radii, 1.321 Earth masses, 12.35-day orbit, and outer habitable-zone conditions.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Distance | 40.66 ly | ± 0.04 ly | Gaia DR3 trigonometric parallax of host star | definitive | ESA Gaia Archive — Data Release 3 |
| Orbital Period | 12.35245 d | ± 0.00006 d | Multi-epoch transit or astrometric orbital fitting | definitive | NASA Exoplanet Archive |
| Semi-Major Axis | 0.04683 AU | ± 0.0004 AU | Keplerian third-law solution from stellar mass and orbital period | definitive | NASA Exoplanet Archive |
| Planetary Mass | 1.321 M⊕ | ± 0.038 M⊕ | Radial velocity or photodynamical transit-timing variations | definitive | NASA Exoplanet Archive |
| Planetary Radius | 1.129 R⊕ | ± 0.015 R⊕ | Transit depth photometry combined with Gaia stellar radius | definitive | NASA Exoplanet Archive |
| Equilibrium Temperature | 199 K | ± 4 K | Radiative equilibrium calculation from bolometric stellar insolation | high-confidence | NASA Exoplanet Archive |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots TRAPPIST-1 g — Largest TRAPPIST-1 Planet Data at RA 23h 06m 29.38s, Dec -05° 02′ 28.5″ within Aquarius, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
At 1.129 Earth radii and 1.321 Earth masses, TRAPPIST-1 g ranks as the physically largest member of the seven-planet family, matching planet b in mass while exceeding it slightly in diameter. Its compressed density of roughly 5.06 grams per cubic centimeter lies well below the pure silicate-iron curve for a 1.3-Earth-mass body, pointing toward an interior enriched with up to five percent water by mass or a substantial high-molecular-weight volatile envelope.
Orbiting 0.0468 astronomical units from its red dwarf host with a period of 12.352 days, this sixth planet receives roughly one-quarter of the solar irradiance that warms Earth. Its equilibrium temperature hovers near 199 K, placing it right at the outer maximum-greenhouse edge of the habitable zone. Sustaining surface liquid water at this distance would require a dense carbon dioxide atmosphere supplemented by trace volcanic gases.
Sandwiched between planet f in a close 4:3 period ratio and outermost planet h in a 3:2 ratio, TRAPPIST-1 g acts as the dynamical heavyweight of the outer system. Its deep 0.76-percent, 68-minute transits provide high signal-to-noise anchor points for photodynamical models that constrain the masses and eccentricities of the entire resonant chain.
Practical Visual Observing Guide
- Produces the deepest outer-system transit (~7,550 ppm) lasting roughly 68 minutes every 12.35 days.
- Coupled in a tight 4:3 mean-motion resonance with TRAPPIST-1 f and a 3:2 resonance with planet h.
- Monitored in infrared transmission spectroscopy campaigns to test for methane, water, and carbon dioxide features.
Catalog Cross-Identifications & Aliases
Common Aliases: TRAPPIST-1g · 2MASS J23062928-0502285 g
| Catalog Authority | Identifier |
|---|---|
| NASAEXOPLANET | TRAPPIST-1 g |
| SIMBAD | TRAPPIST-1 g |
Related Objects, Comparisons & Guides
TRAPPIST-1 f — Cool Habitable-Zone Exoplanet
Reference data for TRAPPIST-1 f: Earth-twin radius, 9.21-day resonant orbit, volatile-rich interior models, and equilibrium temperature.
TRAPPIST-1 e (Temperate Terrestrial World)
Coordinates, Gaia distance (12.47 pc), 6.10-day orbital period, mass 0.692 M⊕, radius 0.920 R⊕, and JWST transit spectroscopy for TRAPPIST-1 e.
LHS 1140 b — Temperate Super-Earth Data
Reference profile for LHS 1140 b: refined mass and radius, 24.7-day habitable-zone orbit in Cetus, water-rich interior, and JWST spectroscopy.
Exoplanet Transit & Radial Velocity Methods
How astronomers detect and characterize exoplanets using photometric transit depth ((Rp/R*)²), Doppler radial velocity (M sin i), and JWST transmission spectra.
Measurement Uncertainty & Optics in Astronomy
How random vs systematic errors, asymmetric error bars, model dependencies, and optical aperture/exit-pupil limits shape astronomical measurements.
Scientific Sources & Dataset Provenance
- NASA Exoplanet Archive (2026-10-01 snapshot): Akeson, R. L., et al. 2013, PASP, 125, 989; NASA Exoplanet Archive (IPAC/Caltech) — NASA Exoplanet Science Institute (NExScI / Caltech / IPAC)
- ESA Gaia Archive — Data Release 3 (DR3 (2022-06-13)): Gaia Collaboration, Vallenari, A., et al. 2023, A&A, 674, A1 (Gaia Data Release 3) — European Space Agency / Gaia DPAC