About the image. Drawn with Alpha Centauri A and B close together and Proxima as a small red point far away. In reality Proxima is about 13 000 times as far from the pair as Earth is from the Sun, so the distance is shortened here. Surface details are imagined.
To the naked eye from the southern hemisphere, Alpha Centauri is a single brilliant star, the third-brightest in the night sky after Sirius and Canopus. A small telescope splits it in two, and a third, much fainter star sits off to the side. Together they are our closest neighbours: the nearest stars to the Sun.
A and B
Alpha Centauri A and B are both similar to the Sun. A is slightly larger and heavier, a yellow star about 1.5 times as bright. B is slightly smaller and cooler, orange, and about half as bright. They circle each other every 79.8 years on a stretched orbit that brings them as close as about 11 times the Earth–Sun distance and as far apart as 36. Both are about 6.2 billion years old, a little older than the Sun, and they lie 4.344 light-years away.
Proxima
The third star, Proxima Centauri, was discovered in 1915. It is a small, dim red dwarf with about an eighth of the Sun’s mass, far too faint to see without a telescope. It lies about 13 000 times as far from A and B as Earth is from the Sun and takes over half a million years to complete one orbit around them. It happens to be on the side of the system facing us, which makes it, at 4.2465 light-years, the closest star of all.
Planets
Proxima has at least two planets. Proxima b, found in 2016, is about the mass of Earth and orbits in the zone where liquid water could exist. Proxima d is smaller, about a quarter of Earth’s mass, on a 5-day orbit. A third, Proxima c, has been proposed but not confirmed.
In August 2025 astronomers using the James Webb Space Telescope reported a possible giant planet around Alpha Centauri A, seen once in 2024. Later observations did not recover it, possibly because it had moved too close to the star. It remains a candidate.
Going there
At the speed of Voyager 1, about 17 kilometres per second, the trip would take some 77 000 years. In 2016 the Breakthrough Starshot project proposed sending tiny probes on laser-driven sails at a fifth of the speed of light, reaching Alpha Centauri in about 20 years. The project has since been put on hold.
How far out it would be
Alpha Centauri goes around once every 80 years, at 23.299 AU from its star. Dashed circles show Jupiter and Saturn around the Sun, on the same scale.
Earth days passing: 0
To scale · radius, Sun = 1Sun: 1.00 · Alpha Centauri A: 1.22 · Alpha Centauri B: 0.86
How hot is it?
Earth (average)288 K · 15 °C
Water boils373 K · 100 °C
Venus surface737 K · 464 °C
Iron melts1 811 K · 1 540 °C
Sun's surface5 772 K · 5 500 °C
Alpha Centauri5 748 K · 5 470 °C
Alpha Centauri: surface temperature of Alpha Centauri A. Logarithmic scale from 100 K to 10 000 K. Reference values: NASA, IAU.
How long to get there?
Alpha Centauri is about 4.344 light-years away.
Light299 792 km/s4.3 years
Breakthrough Starshotplanned light sail, 20% of light speed22 years
Parker Solar Probefastest spacecraft so far, 192 km/s6 783 years
Voyager 1leaving the Solar System, 17 km/s76 606 years
At Voyager 1's speed the trip would take about 958 human lifetimes of 80 years. Bars are on a logarithmic scale. Speeds: NASA, Breakthrough Initiatives.
Gallery
A large yellow star and a smaller orange star side by side, with a tiny red star far off in the upper right, an impression of the three stars of Alpha Centauri. AI-generated painting.A large golden sun and a small orange sun in a dark sky above a rocky, reddish-brown landscape, an impression of the sky of a planet in the Alpha Centauri system. AI-generated painting.Alpha Centauri, 3D artist's impression, rendered from the interactive model.Alpha Centauri, 3D artist's impression, from another angle, rendered from the interactive model.Alpha Centauri, 3D artist's impression, close-up, rendered from the interactive model.
Timeline
1689Jean Richaud sees it is a double star.
1839Thomas Henderson measures its distance.
1915Robert Innes discovers Proxima Centauri.
2016Proxima b is discovered; Breakthrough Starshot is announced.
2025JWST reports a planet candidate around Alpha Centauri A.
Questions people ask
What is the closest star to Earth?
After the Sun, Proxima Centauri, 4.2465 light-years away.
How far is Alpha Centauri?
Alpha Centauri A and B are 4.344 light-years away.
Does Alpha Centauri have planets?
Yes. Proxima has two confirmed planets. A planet candidate around Alpha Centauri A was reported in 2025 but has not been confirmed.