Stars · the nearest

Proxima Centauri: the nearest star to the Sun

Proxima Centauri, an orange-red dwarf star with a sprinkling of dark spots, with the Milky Way behind it

Proxima Centauri is the nearest star to the Sun, 4.25 light-years away: light from it has been travelling for four years and three months. It is a red dwarf too faint to see without a telescope, and it has at least two planets, one of them an Earth-sized world in the zone where water could be liquid. In Exo-View you can fly there from the Sun.

Fly to Proxima Centauri See the Milky Way

Distance: 4.25 light-years, about 40 trillion km
Kind: Red dwarf, spectral type M5.5
Size: 0.15 times the Sun's width, about one and a half times Jupiter's
Surface temperature: About 3,000 K, against the Sun's 5,800 K
Brightness: About 1/600 of the Sun's total light; magnitude 11, far below the naked-eye limit
Spin: Once in about 83 days
Planets: Proxima b, 11.2-day orbit, about Earth's mass; Proxima d, 5-day orbit, about a quarter of Earth's mass

The third star of Alpha Centauri

To the naked eye the nearest star system is Alpha Centauri, the bright point in the southern constellation of Centaurus, which is really two Sun-like stars close together. Proxima is a faint third member, found in 1915, circling the pair at a distance of about 13,000 times the gap between the Earth and the Sun, taking roughly half a million years to go round.

Its planets

In 2016 astronomers announced Proxima b, found by the way Proxima wobbles as it pulls on its star. It is at least about as heavy as the Earth, circles in 11 days, and sits in the habitable zone, where it gets about as much warmth as Earth does. It is very close to its star, so it is probably locked with one face to it, and Proxima's flares, which can double its brightness in minutes, would bathe it in X-rays. Whether it has air or water is unknown. In 2022 a smaller planet, Proxima d, was found closer in, a quarter of the Earth's mass.

How long to get there

Light takes 4.25 years. The fastest spacecraft that have left the solar system, the Voyagers, travel at about 17 km/s, and at that speed the journey would take about 75,000 years. That is why the star is a target for ideas, such as tiny sails pushed by lasers, rather than for a mission.

In Exo-View

The key below flies from the Sun to Proxima Centauri. Its two planets are drawn in their orbits, labelled as an illustration of the figures: nobody has a picture of an exoplanet, only a wobble in a star's light.