StarAlpha Centauri system
Proxima Centauri
The nearest star to the Sun: a small, cool red dwarf only 4.24 light-years away, unusually active for its age, and circled by two confirmed planets and one candidate.
- Star type
- M5.5Ve red dwarf
- Distance
- 4.2465 light-years · 1.301 parsecs
- Mass
- 0.122 solar masses
- Mean radius
- 0.154 solar radii
- Luminosity
- About 0.0017 solar luminosities
- Surface temperature
- About 3,040 K
- Rotation
- About 83 days
- Age
- About 4.8 billion years
The nearest star
Proxima Centauri lies in the constellation Centaurus, close enough that its light reaches us in 4.24 years. It is gravitationally associated with Alpha Centauri A and B, the bright pair that dominates the system, on a very long and poorly known orbit.
Despite its proximity, Proxima is far too faint to see with the unaided eye. Its apparent brightness is only about magnitude 11, and in ordinary images it is an unresolved point of light rather than a disk.
Small, cool, and long-lived
Proxima is an M5.5Ve dwarf: the “e” denotes emission lines from an active chromosphere. It has roughly one-eighth of the Sun’s mass and less than one-sixth of its radius. Its surface is about 3,040 K, cool enough for the star to glow a deep orange-red.
Low-mass stars burn their hydrogen slowly. Proxima is already about 4.8 billion years old, yet it is expected to remain on the main sequence for trillions of years. Red dwarfs like it are the most common stars in the Galaxy, even though none are visible to the naked eye from Earth.
A flare star
Proxima’s deep convection zone and rapid rotation generate a strong magnetic field. Starspots rotate across its surface, and magnetic reconnection produces flares that brighten the star across X-ray, ultraviolet, optical, and radio wavelengths. Its activity cycle has been the subject of long-running monitoring campaigns.
Flares and coronal mass ejections can erode or chemically alter a planet’s atmosphere. That makes Proxima b an important test case: it sits in the star’s habitable zone, but habitability depends on how much atmosphere survives the stellar weather.
Worlds around Proxima
The system contains two confirmed planets and one candidate. The inner planet, Proxima d, completes an orbit in about five days. Proxima b orbits in about 11.2 days and receives roughly 70% of the stellar flux Earth receives from the Sun. The outer candidate, Proxima c, has a proposed orbit of about 1,900 days and remains unconfirmed.
How we study it
Radial-velocity spectrographs such as ESPRESSO and NIRPS measure the star’s tiny wobble caused by orbiting planets. X-ray observatories including XMM-Newton track flares and the hot corona; ALMA probes millimeter emission and the outer system; and high-resolution imaging campaigns attempt to resolve the star’s environment directly.
Because Proxima is unresolved in ordinary photographs, the medallion on this page is an illustration of a cool red dwarf, not a photograph. The system diagram on the Proxima system page is likewise illustrative.
Recent publications
| Year | Paper | Venue | Link |
|---|---|---|---|
| 2026 | Titanium Oxide Absorption as a Proxy to Detect Long term Variation and Activity Cycle in Proxima Centauri | arXiv preprint | arXiv |
| 2026 | Star-planet interaction in the Proxima system | arXiv preprint | arXiv |
| 2025 | Time-resolved X-ray spectra of Proxima Centauri as seen by XMM-Newton | arXiv preprint | arXiv |
| 2025 | The Proxima Centauri Campaign — First Constraints On Millimeter Flare Rates from ALMA | arXiv preprint | arXiv |
| 2025 | Modelling magnetic star-planet interaction in the iconic M dwarfs Proxima Centauri, YZ Ceti and GJ 1151 | arXiv preprint | arXiv |
| 2025 | Suárez Mascareño et al., NIRPS confirmation and refined mass for Proxima b | A&A 700, A11 | DOI |
Compiled 20 October 2026. Preprints are labelled; links resolve to the arXiv or publisher record.