TRAPPIST-1 e
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.
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 |
|---|---|---|---|---|---|
| Orbital period | 6.099615 d | ± 0.000011 d | Multi-telescope transit timing (Spitzer/Kepler/HST/JWST) | definitive | NASA Exoplanet Archive |
| Planetary radius | 0.92 R⊕ | ± 0.013 R⊕ | Transit photometry (R_p / R_★ = 0.0689) | definitive | NASA Exoplanet Archive |
| Planetary mass | 0.692 M⊕ | ± 0.022 M⊕ | 7-planet resonant transit-timing variations (Agol et al. 2021) | definitive | NASA Exoplanet Archive |
| Orbital semi-major axis | 0.02925 AU | ± 0.00025 AU | Keplerian dynamical solution around 0.0898 M☉ host star | definitive | NASA Exoplanet Archive |
| Zero-albedo equilibrium temperature | 251.3 K | ± 4.9 K | Derived from 0.662 S⊕ stellar insolation | model-dependent | NASA Exoplanet Archive |
| Host star distance (Gaia DR3) | 12.467 pc | ± 0.006 pc | Gaia DR3 astrometric parallax (80.21 ± 0.04 mas, 40.66 ly) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots TRAPPIST-1 e (Temperate Terrestrial World) at RA 23h 06m 29.28s, Dec -05° 02′ 28.6″ 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
TRAPPIST-1 e is the fourth planet from the ultracool M8 V dwarf star TRAPPIST-1, located 12.467 ± 0.006 parsecs (40.66 light-years) away in Aquarius. Discovered in 2017 using the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) and NASA's Spitzer Space Telescope, TRAPPIST-1 e orbits inside a compact Laplace mean-motion resonant chain of seven Earth-sized worlds, all packed closer to their miniature 2,566 K red-dwarf sun than Mercury is to ours.
Completing one orbit every 6.0996 days at a distance of just 0.02925 AU (4.38 million kilometers), TRAPPIST-1 e receives 66.2% of Earth's solar flux, placing it squarely in the conservative liquid-water habitable zone with a zero-albedo equilibrium temperature of 251 K (−22 °C). Because the seven planets gravitationally tug on one another at every conjunction, their transit times shift by minutes to hours; inverting those transit-timing variations yields a rocky, iron-core bulk density of 4.89 g/cm³ (0.692 Earth masses inside 0.920 Earth radii)—the closest known analog to Earth's uncompressed interior composition.
Because TRAPPIST-1 has a radius only 11.9% that of the Sun (slightly larger than Jupiter), TRAPPIST-1 e blocks 0.475% (4,750 ppm) of the star's light during every 57-minute transit—nearly 56 times deeper than an Earth-across-the-Sun transit—making it the premier terrestrial target for atmospheric transmission spectroscopy with the James Webb Space Telescope.
Practical Visual Observing Guide
- The host star TRAPPIST-1 is an ultra-faint M8 V red dwarf shining at visual magnitude V = 18.80 (though much brighter in the near-infrared at J = 11.35 and K = 10.30).
- Visual observation of the host star requires a 500 mm (20-inch) or larger telescope under dark skies, while amateur CCD/CMOS observers with 250–350 mm telescopes equipped with near-IR/I-band filters can record the star's 11.3-mag infrared flux and detect the 0.005-magnitude transit dip.
Catalog Cross-Identifications & Aliases
Common Aliases: 2MASS J23062928-0502285 e
| Catalog Authority | Identifier |
|---|---|
| NASAEXOPLANET | TRAPPIST-1 e |
| SIMBAD | TRAPPIST-1 e |
| WIKIDATA | Q28822650 |
Related Objects, Comparisons & Guides
Proxima Centauri b (Nearest Exoplanet)
Coordinates, ESPRESSO minimum mass (1.07 M⊕), 11.186-day habitable-zone orbit at 0.04856 AU, and stellar flare environment of Proxima Centauri b.
K2-18 b (Temperate Sub-Neptune in Leo)
Coordinates, Gaia DR3 distance (38.07 pc), 32.94-day habitable-zone orbit, 8.63 M⊕ mass, 2.61 R⊕ radius, and JWST CH4/CO2 spectrum of K2-18 b.
WASP-39 b (JWST Benchmark Saturn Exoplanet)
Coordinates, Gaia DR3 distance (213 pc), 4.055-day period, 0.28 M♃ mass, 1.27 R♃ radius, and JWST CO2/SO2 photochemical spectrum of WASP-39 b.
51 Pegasi b (Dimidium First Hot Jupiter)
Coordinates, Gaia DR3 distance (15.46 pc), 4.2308-day orbital period, Nobel-winning radial-velocity discovery, and observing guide for 51 Pegasi b.
TRAPPIST-1 e vs Proxima Centauri b Comparison
Compare the two benchmark temperate M-dwarf rocky exoplanets TRAPPIST-1 e and Proxima Centauri b: detection method, mass, radius, and habitability.
Trigonometric Parallax, Parsecs & Gaia DR3
How trigonometric parallax (d_pc = 1 / p_arcsec), the distance modulus equation, Hipparcos, and Gaia DR3 microarcsecond astrometry measure cosmic distances.
Measurement Uncertainty & Optics in Astronomy
How random vs systematic errors, asymmetric error bars, model dependencies, and optical aperture/exit-pupil limits shape astronomical measurements.
Confirmed Exoplanets & Host Systems Catalog
Curated NASA Exoplanet Archive reference catalog of benchmark exoplanets: Proxima Centauri b, TRAPPIST-1 e, 51 Pegasi b, HD 209458 b, K2-18 b, and WASP-39 b.
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)
- JWST / MAST Science Archive & Mission Documentation (Cycle 1–4 Public Releases (2022–2026)): Rigby, J., et al. 2023, PASP, 135, 048001 (The Science Performance of JWST as Characterized in Commissioning) — NASA / ESA / CSA / STScI
- 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