Wolf 359 ranks as the fifth closest star to Earth. Only the sun, the binary (double) star Alpha Centauri, and two other stars are nearer. Wolf 359 lies about 7.8 light-years away. One light-year is the distance light travels in a vacuum in a year, about 9.46 trillion kilometers. As seen from Earth, Wolf 359 appears in the constellation Leo, the Lion. The star takes its name from the German astronomer Max Wolf, who discovered it in 1918 in photographs taken through a telescope. Wolf 359 shines too faintly to be seen with the unaided eye.
Astronomers classify Wolf 359 as a type of small, faint star called a red dwarf. Wolf 359 has about 1/10 the sun’s mass (amount of matter). Its diameter measures about 1/5 that of the sun. Wolf 359’s 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 relatively cool surface, Wolf 359 gives off about 1/50,000 as much light as does the sun.
The surface of Wolf 359 occasionally gives off violent eruptions called flares. These flares appear much more pronounced than those that occur on the sun. Flares on Wolf 359 sometimes cause the star’s brightness to more than double in just a few minutes. For this reason, astronomers refer to Wolf 359 as a flare star.
See also Star (table: The 10 known stars nearest Earth) .
