Wolf 359

Ownership: UCP
Spectral class: M6.5 Ve red dwarf

U-B color index: +1.54

B-V color index: +2.01

Variable type: Flare star
Absolute magnitude: 16.64
Temperature: 2,800 ± 100 K
Rotation: <3.0 km/s
Age: 1–3.5 × 10⁸ years
Diameter: 150,000 km

Wolf 359, also known as Gliese 406, is an extremely faint class M6 red dwarf in the immediate neighborhood of the Sol system. It is a flare star that undergoes random increases in luminosity because of magnetic activity on its surface.

The projected rotational velocity of this star's equator is less than 3 km/s; below the threshold of detection through spectral line broadening. The outer atmosphere of Wolf 359 is sufficiently cool that molecular lines appear in the spectrum. The space velocity of this star suggests that it belongs to the population of old disk stars. However, evolutionary models suggest that it is a relatively young star with an age of less than a billion years.

It is classified as a UV Ceti-type flare star, and has a relatively high flare rate. Observations have detected 32 flare events within a two hour period, with energies of 10²⁷ ergs (10²⁰ joules) and higher. The mean magnetic field has a strength of about 2.2 kG, but this varies significantly on time scales as short as six hours.