---
title: "Alpha Centauri: facts, distance and size – Krillion Space"
description: "Alpha Centauri is the closest star system to the Sun: two Sun-like stars and the red dwarf Proxima. Its distance, size and sourced facts."
url: https://krilion.app/atlas/alpha-centauri
language: en-US
---

# Alpha Centauri

Triple star system. Depth 17 on the Krillion Space voyage, in the Nearby stars.

Alpha Centauri is the closest star system to the Sun: a pair of Sun-like stars, A and B, with a small red dwarf, Proxima Centauri, circling far outside them. Because A and B are so similar to the Sun and so close to us, they are prime targets in the search for planets and life beyond the solar system.

![Alpha Centauri at depth 17 in Krillion Space, painted by the game (an illustration, not a photograph).](https://krilion.app/assets/atlas/alpha-centauri.webp)

## Fact sheet

- **Type:** Triple star system (G-type and K-type main-sequence stars plus a red dwarf)
- **Distance:** About 4.3 light-years from the Sun (the A and B pair)
- **Size:** Alpha Centauri A is about 1.2 times the Sun's radius and 1.08 times its mass; Alpha Centauri B is about 0.86 times the Sun's radius and 0.91 times its mass
- **Constellation:** Centaurus
- **Position in the sky:** Right ascension 14h 40m, declination −60° 50′
- **Seeing it from Earth:** Easily seen with the naked eye as one bright star from the Southern Hemisphere and low northern latitudes; it never rises for most of the Northern Hemisphere, and splitting A from B needs a small telescope.
- **On the voyage:** Depth 17, in the Nearby stars section of the route, between the Oort Cloud and Proxima Centauri b

## Things to know

- The system has three stars: Alpha Centauri A is a G-type star a little heavier than the Sun, B is a slightly cooler K-type star a little lighter than the Sun, and Proxima Centauri is a small red dwarf. ([NASA](https://svs.gsfc.nasa.gov/20377))
- Alpha Centauri A and B circle each other about once every 80 years, while Proxima orbits the pair from more than 10,000 times the Earth-Sun distance. ([NASA Chandra](https://chandra.harvard.edu/photo/2018/alphacen/))
- Proxima is currently the single closest star to the Sun, with the A and B pair a very close second. ([NASA Chandra](https://chandra.harvard.edu/photo/2018/alphacen/))
- In 2024 the James Webb Space Telescope spotted a possible Saturn-mass gas giant orbiting Alpha Centauri A, but follow-up looks in 2025 did not see it again, so it remains an unconfirmed candidate. ([ESA/Webb](https://esawebb.org/news/weic2515/))
- Alpha Centauri A ranks as the third-brightest star in the night sky, and the system lies so far south that it is seen mainly from the Southern Hemisphere. ([ESA/Webb](https://esawebb.org/news/weic2515/))

## Sources

- [NASA Goddard SVS – Alpha Centauri Stellar System](https://svs.gsfc.nasa.gov/20377)
- [Chandra X-ray Observatory – Alpha Centauri (2018)](https://chandra.harvard.edu/photo/2018/alphacen/)
- [ESA/Webb – Webb finds new evidence for planet around closest solar twin (weic2515)](https://esawebb.org/news/weic2515/)
- [Akeson et al. 2021, AJ – Precision millimeter astrometry of the Alpha Centauri AB system (arXiv)](https://arxiv.org/abs/2104.10086)

## On the route

- Previous landmark: [Oort Cloud](https://krilion.app/atlas/oort-cloud)
- Next landmark: [Proxima Centauri b](https://krilion.app/atlas/proxima-b)
- [The whole Star Atlas](https://krilion.app/atlas)
- [Fly the voyage yourself](https://krilion.app/d/): every right answer warps your ship one stop deeper.