Proxima Centauri b
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.
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 | 11.1868 d | ± 0.0029 d | HARPS, UVES & ESPRESSO extreme-precision radial velocity | definitive | NASA Exoplanet Archive |
| Minimum planetary mass (M sin i) | 1.07 M⊕ | ± 0.06 M⊕ | ESPRESSO radial-velocity semi-amplitude K = 1.24 ± 0.07 m/s (Faria et al. 2022) | high-confidence | NASA Exoplanet Archive |
| Orbital semi-major axis | 0.04856 AU | ± 0.0003 AU | Keplerian orbit around 0.1221 M☉ host star | definitive | NASA Exoplanet Archive |
| Equilibrium temperature (Bond albedo 0.3) | 234 K | ± 10 K | Derived from 0.65 S⊕ bolometric irradiance | model-dependent | NASA Exoplanet Archive |
| Distance in light-years | 4.2465 ly | ± 0.0003 ly | Gaia DR3 parallax of host star Proxima Centauri (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Proxima Centauri b (Nearest Exoplanet) at RA 14h 29m 42.95s, Dec -62° 40′ 46.1″ within Centaurus, 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
Proxima Centauri b, announced by Guillem Anglada-Escudé and the Pale Red Dot team in August 2016 using the HARPS and UVES spectrographs in Chile, is the closest exoplanet to our Solar System at just 4.2465 light-years (1.302 parsecs). Subsequent observations with the ultra-stable ESPRESSO spectrograph on the Very Large Telescope refined its Doppler reflex wobble to a semi-amplitude of 1.24 ± 0.07 meters per second—barely the speed of a brisk human walk.
Orbiting its M5.5 Ve red-dwarf host at a distance of 0.04856 AU (7.26 million kilometers, roughly 5% of the Earth–Sun distance), Proxima b completes a full year in just 11.1868 Earth days. Because Proxima Centauri radiates only 0.155% of the Sun's total energy, this tight orbit places Proxima b inside the star's habitable zone, receiving ~65% of Earth's total solar irradiance with an equilibrium temperature near 234 K (−39 °C).
Whether Proxima b can retain a surface atmosphere or liquid water is one of exoplanet science's sharpest debates: orbiting so close to a flare-active red dwarf, the planet is likely tidally locked (or in a 3:2 spin-orbit resonance like Mercury) and receives roughly 400 times more X-ray and extreme-ultraviolet flux than Earth. Upcoming 39-meter Extremely Large Telescope (ELT) high-contrast spectrographs aim to resolve Proxima b directly at its ~37-milliarcsecond maximum angular separation.
Practical Visual Observing Guide
- Proxima b cannot be resolved visually in amateur telescopes (its maximum angular separation from Proxima Centauri is 0.037 arcseconds), but observers south of +27°N can view its 11.13-magnitude host star in an 80–100 mm telescope.
Catalog Cross-Identifications & Aliases
Common Aliases: Alpha Centauri C b · GJ 551 b
| Catalog Authority | Identifier |
|---|---|
| NASAEXOPLANET | Proxima Cen b |
| SIMBAD | Proxima Cen b |
| WIKIDATA | Q26690172 |
Related Objects, Comparisons & Guides
Proxima Centauri (Nearest Star to Sun)
Coordinates, Gaia DR3 parallax (768.07 mas, 4.2465 ly), magnitude 11.13, flare activity, and planetary system guide for Proxima Centauri.
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.
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.
Tau Ceti (HD 10700 Nearby Solar Analog)
Coordinates, Gaia DR3 parallax (273.81 mas, 11.91 ly), magnitude 3.50, debris disk, and observing guide for G8V star Tau Ceti.
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.
Proper Motion, Radial Velocity & Redshift
How astronomers combine tangential proper motion (mas/yr), Doppler radial velocity (km/s), and cosmological redshift (z) to reconstruct 3D space motion.
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.
Bright, Multiple & Variable Stars Catalog
Cross-reference catalog of solar-neighborhood and navigation stars across Bayer, Henry Draper (HD), Hipparcos (HIP), WDS, and Gaia DR3 designations.
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)
- 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
- SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg