Alpha Centauri
Alpha Centauri is the nearest star system to the Sun, 4.37 light-years away. It is a triple system: the Sun-like pair Alpha Centauri A (G2V) and B (K1V), which orbit each other every ~80 years, plus the faint red dwarf Proxima Centauri — the single closest star to the Sun, and host to the two confirmed planets Proxima b and Proxima d. No confirmed planets are known around A or B.
Key facts
Science
Classification
- Type
- Triple star system
- Stars
- Alpha Centauri A (G2V), B (K1V), Proxima Centauri (M5.5Ve)
Planets
- Confirmed planets
- 2 · Proxima b and Proxima d
- Around A and B
- None confirmed
Distance & age
- Distance
- 4.37 light-years (A/B); 4.24 (Proxima) · the closest star system to the Sun
- Age
- ~5.3 billion years · estimated — a little older than the Sun
How we know
- Note
- Planet confirmations follow the NASA Exoplanet Archive (checked 2026-07-02): only Proxima b and d are confirmed. The disputed 'Proxima c' is not confirmed and is not shown. On the map Proxima is placed near the A–B pair for usability; it truly lies about 12,950 AU (0.21 light-years) away.
Discovery & history
- Name
- 'Alpha Centauri' is the brightest star of the constellation Centaurus (Bayer designation, 1603). Its stars carry the IAU proper names Rigil Kentaurus (A), Toliman (B) and Proxima Centauri (C).
The bright star of Centaurus has been known since antiquity. In 1689 Jean Richaud found it to be a double star; in 1839 Thomas Henderson's parallax revealed it as our nearest stellar neighbour. Robert Innes discovered the faint companion Proxima in 1915, and in 2016–2022 ESO's HARPS and ESPRESSO spectrographs confirmed the planets Proxima b and d.
Images
Images from open archives · credit shown per image