Star that varies in brightness repeatedly but sporadically, sometimes by more than one magnitude, within a few minutes. The cause is thought to be the eruption of flares like those observed on the Sun but much larger (see solar flare). Proxima Centauri, in Alpha Centauri, the closest star to the Sun, is a flare star.
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Most flare stars are dim red dwarfs, although recent research indicates that less massive brown dwarfs might also be capable of flaring. The more massive RS Canum Venaticorum variables (RS CVn) are also known to flare, but it is understood that these flares are induced by a companion star in a binary system which causes the magnetic field to become tangled. Additionally, nine stars similar to the Sun have also been seen to undergo flare events. It has been proposed that the mechanism for this is similar to that of the RS CVn variables in that the flares are being induced by a companion, namely an unseen Jupiter like planet in a close orbit .
The Sun's nearest stellar neighbor Proxima Centauri is a flare star, as is another near neighbor; Wolf 359. Barnard's Star, the second nearest star system, is also suspected of being a flare star. Flare stars are intrinsically faint, but have been found to distances of 1000 light years from Earth .