Lalande 21185 ranks as the sixth closest star to Earth. The star lies about 8.3 light-years away. One light-year equals the distance light travels in a vacuum in a year, about 9.46 trillion kilometers. As seen from Earth, Lalande 21185 lies in the southeastern part of the constellation Ursa Major, the Great Bear. The French astronomer Joseph-Jérôme Lefrançais de Lalande first cataloged the star in 1801.
Astronomers classify Lalande 21185 as a type of small, faint star called a red dwarf. It has about half the sun’s mass (amount of matter). The diameter of Lalande 21185 also measures about half that of the sun. Its reddish color results from relatively low surface temperatures, around 3000 K. One kelvin (K) equals one Celsius degree above absolute zero (–273.15 °C). Because of its small size and cool surface, Lalande 21185 gives off about 1/30 as much light as does the sun. It cannot be seen with the unaided eye.
The surface of Lalande 21185 occasionally gives off violent eruptions called flares. These flares may appear much more pronounced than those that occur on the sun. Flares on Lalande 21185 sometimes cause the star’s brightness to increase dramatically in just a few minutes. For this reason, astronomers refer to Lalande 21185 as a flare star.
See also Star (table: The 10 known stars nearest Earth) ; Ursa Major .
