Flare stars are main-sequence stars that abruptly brighten by several magnitudes for a very sort time, then quickly revert to their usual brightness. These flare-ups are erratic, with no detectable periodicity. There is also a large increase in the ultraviolet (UV) in many cases. Typical flare stars such as AD Leonis and YX Canoris exhibit small microflares as often as several times each night, while larger spectacular flares are observed with frequencies of once a week to once a month.

Many astronomers believe that the flare phenomenon represents a localized release of energy within the star atmosphere, similar to flares on the Sun. From this point of view, the Sun is a flare star, but the brightness of a flare star so small compared with the Sun's total brightness, that the solar luminosity is not appreciably increase during a flare. One of the Sun's nearest neighbors, Proxima Centauri, is a flare star.

Copyright (c) 1997-99 Michael Erlewine