Proxima Centauri
Star
Proxima Centauri — a small M5.5 red dwarf and the nearest star to the Sun, 4.246 light-years away. It is gravitationally bound to the A–B pair, orbiting them at about 12,950 AU (0.21 light-years) every ~511,000 years — shown far closer here for usability. A violent flare star, it hosts the nearest known exoplanets.
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Key facts
Mass
2.43 × 10²⁹ kg
0.122 M☉
Radius
107,277 km
15% of the Sun's radius
Surface temperature
2,992 K (2719 °C)
Spectral type
M5.5Ve (red dwarf, emission-line flare star)
Science
Physical
- Mass
- 2.43 × 10²⁹ kg · 0.122 M☉
- Radius
- 107,277 km · 15% of the Sun's radius
- Density
- 46,960 kg/m³ · 47× water
- Spectral type
- M5.5Ve (red dwarf, emission-line flare star)
Rotation
- Equatorial period
- 84.9 days
- Note
- Rotation ≈ 85 days, yet violently active: flares can briefly brighten the star several-fold, bathing its planets in X-rays and UV
Composition
- By mass
- Fully convective hydrogen/helium dwarf — energy stirs from core to surface with no radiative zone. Known only from spectroscopy; its feeble output is mostly infrared
Temperature
- Surface
- 2,992 K (2719 °C)
Radiation & temperature
- Luminosity
- 6.00 × 10²³ W · 0.00157 L☉
- Surface temperature
- 2,992 K (2719 °C)
- Peak wavelength
- 969 nm · near-infrared (mostly invisible to the eye)
Discovery & history
- Discovered
- October 12, 1915
- By
- Robert T. A. Innes
- Method
- Photographic plates
- Name
- Proxima — Latin for 'nearest', proposed by Innes himself. Formally adopted as the IAU proper name in 2016.
Discovered in 1915 by Robert T. A. Innes at the Union Observatory, Johannesburg, during a proper-motion survey: a faint red star moving across the sky in lockstep with Alpha Centauri. Its parallax proved it marginally CLOSER than the bright pair — the nearest star to the Sun, a title it will keep for roughly the next 25,000 years.
Images
Images from open archives · credit shown per image