Proxima Centauri
Proxima Centauri is a star in the constellation Centaurus, magnitude 11.1.
The nearest star to the Sun: a tiny, flaring red dwarf with an Earth-mass planet in its habitable zone.
In 1915 Robert Innes, at the Union Observatory in Johannesburg, found a faint red star near Alpha Centauri sharing its motion across the sky. It turned out to be the nearest star of all after the Sun, and its name, Proxima, is Latin for ‘nearest’. It belongs to the Alpha Centauri system, circling the bright pair once in about 550,000 years.
Proxima is a red dwarf with an eighth of the Sun’s mass and a seventh of its diameter — only about one and a half times the width of Jupiter. More than 85% of its energy comes out as infrared. Its whole interior churns, driving a strong magnetic field and violent flares that can reach 27 million kelvins. The same churning keeps fresh hydrogen flowing into its core, so it will keep shining for about four trillion years — hundreds of times the present age of the universe.
In 2016 astronomers found Proxima b, a planet at least as massive as Earth, orbiting every 11.2 days within the star’s habitable zone. Given the flares, whether it could support life is highly uncertain. A second, smaller planet, Proxima d, circles even closer.
Proxima Centauri is 4.2 light-years away: the light we see from it set off in 2022, around the time the James Webb Space Telescope was launched.
Did you know?
- Small but dense. Proxima is on average about 33 times denser than the Sun, and the gravity at its surface is roughly 160 times Earth’s.
- A future blue dwarf. As it slowly turns hydrogen into helium, Proxima will grow smaller and hotter, becoming a ‘blue dwarf’, then end as a white dwarf — without ever becoming a red giant.
An 11th-magnitude red dwarf that needs a telescope, about two degrees south-west of brilliant Alpha Centauri. It looks utterly ordinary — a faint reddish point in a rich Milky Way field — so use a detailed chart to be sure you have the right one.
When and where to see it
It is best placed in the evening sky around May, when it crosses the meridian at about 10 pm local time (around midnight in April). It can be seen from everywhere south of 27°N and never sets south of 27°S.
At its highest it stands below the horizon from 50°N, below the horizon from 35°N, 27° up from the equator, 62° up from 35°S.
Facts
- Type
- Star
- Constellation
- Centaurus
- Designations
- Proxima Cen, Proxima, HIP 70890
- Magnitude
- 11.1
- Position
- RA 14h 29.7m, Dec −62° 41′ (J2000)
- Spectral type
- M5.5Ve
- Colour
- orange-red (B−V 1.82)
- Distance
- 4.2 light-years
- Discovered
- Robert Innes, 1915
Open AstroPilot to see when Proxima Centauri is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.