Proxima Centauri b
Planet· orbits Proxima Centauri
Proxima Centauri b — the nearest known exoplanet, 4.25 light-years away. A roughly Earth-mass world (minimum mass 1.06 Earths) orbiting inside Proxima Centauri's habitable zone every 11.2 days. It has never been imaged: its true size, surface and atmosphere are unknown.
Open in 3D viewSee Proxima Centauri b in the live, interactive 3D map
Key facts
Minimum mass
6.30 × 10²⁴ kg
1.06 M⊕
Year
11.18 Earth days
Distance from Proxima Centauri
7,264,473 km
Science
Physical
- Minimum mass (m·sin i)
- 6.30 × 10²⁴ kg · 1.06 M⊕
- Radial-velocity detection measures m·sin i; the true mass depends on the unknown orbital inclination.
- Radius
- Not measured
- No transit has been observed, so the radius has never been measured — composition models give 0.94–1.4 Earth radii; the rendered size is that estimate, not data.
Orbital
- Semi-major axis
- 7,264,473 km
- From the NASA Exoplanet Archive (radial-velocity orbit; the orbital inclination is unknown, so the orbit is shown face-on in the zone plane)
- Eccentricity
- 0
- From the NASA Exoplanet Archive (radial-velocity orbit; the orbital inclination is unknown, so the orbit is shown face-on in the zone plane)
- Inclination
- 0.00 °
- From the NASA Exoplanet Archive (radial-velocity orbit; the orbital inclination is unknown, so the orbit is shown face-on in the zone plane)
- Orbital period
- 11.2 days
- From the NASA Exoplanet Archive (radial-velocity orbit; the orbital inclination is unknown, so the orbit is shown face-on in the zone plane)
- Perihelion
- 7,264,473 km
- Computed from the orbital elements
- Aphelion
- 7,264,473 km
- Computed from the orbital elements
- Mean orbital velocity
- 47.2 km/s
- Computed from the orbital elements
Atmosphere
- Composition
- Unknown — no atmosphere has been detected or ruled out. The planet sits in the habitable zone (0.037–0.088 AU) receiving ~65% of Earth's flux, is likely tidally locked, and endures its star's frequent flares — whether it retains an atmosphere is one of the system's open questions.
Composition
- Bulk composition
- Unknown. The minimum mass of 1.06 Earths is consistent with a rocky world, but no spectrum of the planet itself has ever been taken.
- Surface appearance
- Appearance based on ESO/M. Kornmesser's artist's concept. No spacecraft has imaged this world, so its real appearance is unknown — The surface shown is an artistic representation, shown only in Visual mode; Realism shows a plain spectral colour.
Radiation & temperature
- Insolation
- 0.665 S⊕ · 66% of the sunlight Earth receives
- Computed from Proxima Centauri's luminosity and the orbital distance (inverse-square; Earth's sunlight = 1).
- Equilibrium temperature
- 218 K (-55 °C)
- NASA Exoplanet Archive model value (no atmosphere assumed), computed for Proxima's dim red output — not measured.
Discovery & history
- Discovered
- August 24, 2016
- By
- Guillem Anglada-Escudé et al. (ESO, Pale Red Dot)
- Method
- Radial-velocity detection (stellar wobble)
- Name
- Designated 'b' as the first planet found around Proxima Centauri, following the IAU convention of lettering planets in discovery order starting at 'b'.
Announced on 24 August 2016 by Guillem Anglada-Escudé's team after the 'Pale Red Dot' campaign — months of nightly radial-velocity monitoring with ESO's HARPS spectrograph at La Silla, Chile (with UVES at the VLT). The star's spectrum swings by just ~1.4 m/s — walking pace — every 11.2 days, betraying an unseen roughly Earth-mass companion in the habitable zone of the nearest star. It remains the closest exoplanet known.
Images
Images from open archives · credit shown per image