Ross 154 ranks as the ninth closest star to Earth. It lies about 9.7 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, Ross 154 appears in the constellation Sagittarius, the Archer. The star takes its name from the American astronomer Frank E. Ross, who first cataloged it in 1925. Ross 154 shines too faintly to be seen with the unaided eye.
Astronomers classify Ross 154 as a type of small, faint star called a red dwarf. Ross 154 has about 1/6 the sun’s mass (amount of matter). Its diameter measures about 1/4 that of the sun. Ross 154’s reddish color results from relatively low surface temperatures, around 2700 K. One kelvin (K) equals one Celsius degree above absolute zero (–273.15 °C). Ross 154 gives off about 1/250 as much light as does the sun.
Ross 154 exhibits sudden, intense increases in brightness called flares that fade within a few minutes. These flares probably resemble solar flares on the sun. But because Ross 154 is much smaller than the sun, the flares have a much more pronounced effect on its overall brightness. For this reason, astronomers refer to Ross 154 as a flare star.
See also Sagittarius ; Star (table: The 10 known stars nearest Earth) .
