Proxima Centauri b

Planet· orbits the Sun

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

11.19 Earth days

Distance from Proxima Centauri

7,264,473 km

Science

Physical

Minimum mass (m·sin i): 6.30 × 10²⁴ kg · 1.06 M⊕
Radius: Not measured

Orbital

Semi-major axis: 7,264,473 km
Eccentricity: 0
Inclination: 0.00 °
Orbital period: 11.2 days
Perihelion: 7,264,473 km
Aphelion: 7,264,473 km
Mean orbital velocity: 47.2 km/s

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 Vision mode; Realism shows a plain spectral colour.

Radiation & temperature

Insolation: 0.665 S⊕ · 66% of the sunlight Earth receives
Equilibrium temperature: 218 K (-55 °C)

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

Proxima b with its red-dwarf sun low on the horizon — artist's impression, not a photograph (the planet has never been imaged) — ESO / M. Kornmesser (CC BY 4.0) · Wikimedia Commons

Proxima b imagined as an arid rocky world — artist's impression, not a photograph; its true appearance is unknown — ESO / M. Kornmesser (CC BY 4.0) · Wikimedia Commons

Images from open archives · credit shown per image