Third Tuesday 2017-09: Ross 154 Event Cache

Ross 154 (V1216 Sgr) is a star in the southern zodiac constellation of Sagittarius. It has an apparent visual magnitude of 10.44, making it much too faint to be seen with the naked eye. At a minimum, viewing Ross 154 requires a telescope with an aperture of 6.5 cm (3 in) under ideal conditions. The distance to this star can be estimated from parallax measurements, which places it at 9.69 light-years (2.97 parsecs) away from Earth. It is the nearest star in the southern constellation Sagittarius, and one of the nearest stars to the Sun.

Ross 154 was found to be a UV Ceti-type flare star, with a mean time between major flares of about two days. The first such flare activity was observed from Australia in 1951 when the star increased in magnitude by 0.4. Typically, the star will increase by 3–4 magnitudes during a flare. The strength of the star's surface magnetic field is an estimated 2.2 ± 0.1 kG. Ross 154 is an X-ray source and it has been detected by several X-ray observatories. The quiescent X-ray luminosity is about 9 × 1027 ergs s−1. X-ray flare emission from this star has been observed by Chandra observatory, with a particularly large flare emitting 2.3 × 1033 erg.

A stellar classification of M3.5V makes this a red dwarf star that is generating energy through the nuclear fusion of hydrogen at its core. It has an estimated 17% of the Sun's mass and 24% of the Sun's radius, but it is radiating only 0.38% of the luminosity of the Sun. In contrast to the Sun where convection only occurs in the outer layers, a red dwarf with a mass this low will be entirely convective. Based on the relatively high projected rotation, this is probably a young star with an estimated age of less than a billion years. The abundance of elements heavier than helium is about half that in the Sun.