Kepler-186 f
Reference data for Kepler-186 f: 1.17 Earth radii, 129.9-day habitable-zone orbit around an M1 dwarf in Cygnus, and insolation metrics.
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 | 579 ly | ± 6 ly | Gaia DR3 parallax of host star Kepler-186. | definitive | ESA Gaia Archive — Data Release 3 |
| Orbital Period | 129.9441 d | ± 0.0013 d | Multi-epoch transit or astrometric orbital fitting | definitive | NASA Exoplanet Archive |
| Semi-Major Axis | 0.432 AU | ± 0.05 AU | Keplerian third-law solution from stellar mass and orbital period | high-confidence | NASA Exoplanet Archive |
| Planetary Radius | 1.17 R⊕ | ± 0.08 R⊕ | Transit depth photometry combined with Gaia stellar radius | high-confidence | NASA Exoplanet Archive |
| Estimated Mass | 1.44 M⊕ | ± 0.38 M⊕ | Empirical rocky mass-radius relation; radial velocity mass not yet measured. | model-dependent | NASA Exoplanet Archive |
| Equilibrium Temperature | 188 K | ± 16 K | Radiative equilibrium calculation from bolometric stellar insolation | high-confidence | NASA Exoplanet Archive |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Kepler-186 f — First Earth-Size Habitable World at RA 19h 54m 36.65s, Dec +43° 57′ 18.1″ within Cygnus, 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
Validated in April 2014 from four years of NASA Kepler space telescope photometry, Kepler-186 f became the first confirmed exoplanet with a radius comparable to Earth's orbiting inside the conservative habitable zone of a star beyond the Sun. Its host, Kepler-186, is an early M1V dwarf located 579 light-years away in Cygnus with roughly half the Sun's mass and radius. Four smaller, hotter sibling worlds (planets b through e) circle much closer to the star with periods between 3.9 and 22.4 days.
At 1.17 Earth radii, Kepler-186 f sits comfortably below the 1.5-Earth-radius transition threshold where planets begin retaining thick primordial hydrogen-helium envelopes, strongly favoring a rocky silicate-iron or water-enriched interior. It completes an orbit every 129.94 days at a semi-major axis of 0.432 astronomical units—similar to Mercury's distance from the Sun—where it intercepts about 32 percent of Earth's solar flux.
Because it orbits much farther from its M1V host than the ultra-compact planets around late M8 dwarfs, Kepler-186 f lies near the boundary of the tidal spin-synchronization zone. Dynamical simulations show that its rotation may not be fully locked, or that it could maintain a stable low obliquity over billions of years, moderating extreme temperature contrasts between hemispheres.
Practical Visual Observing Guide
- Host star Kepler-186 has an apparent visual magnitude of V ~ 14.62 in Cygnus.
- Transit depth is roughly 520 ppm, far too shallow for amateur equipment and requiring space-based photometry.
- Because of its 579 ly distance and faint host, radial velocity mass measurement remains beyond current spectrographs.
Catalog Cross-Identifications & Aliases
Common Aliases: Kepler-186f · KOI-571.05 · KIC 8120608 f
| Catalog Authority | Identifier |
|---|---|
| NASAEXOPLANET | Kepler-186 f |
| SIMBAD | Kepler-186 f |
Related Objects, Comparisons & Guides
Kepler-452 b — Super-Earth Around a G2 Star
Reference profile for Kepler-452 b: 384.8-day orbit, 1.05 AU separation from a G2V star, 1.63 Earth radii, and validation status.
TOI-700 d — TESS Habitable-Zone Earth Analog
Reference profile for TOI-700 d: 1.07 Earth radii, 37.4-day habitable-zone orbit in Dorado, insolation metrics, and multi-planet context.
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.
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.
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.
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