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Gliese 229 (also written as Gl 229 or GJ 229) is a red dwarf about 19 light years away in the constellation Lepus. It has 58% of the mass of the Sun,〔 69% of the Sun's radius,〔 and a very low projected rotation velocity of 1 km/s at the stellar equator.〔 The star is known to be a low activity flare star, which means it undergoes random increases in luminosity because of magnetic activity at the surface. The spectrum shows emission lines of calcium in the H and K bands. The emission of X-rays has been detected from the corona of this star. These may be caused by magnetic loops interacting with the gas of the star's outer atmosphere. No large-scale star spot activity has been detected. The space velocity components of this star are U = +12, V = –11 and W = –12 km/s. The orbit of this star through the Milky Way galaxy has an eccentricity of 0.07 and an orbital inclination of 0.005.〔 == Substellar companions == A substellar companion was discovered in 1994 and confirmed in 1995 as Gliese 229B, one of the first two instances of clear evidence for a brown dwarf, along with Teide 1. Although too small to sustain hydrogen-burning nuclear fusion as in a main sequence star, with a mass of 20 to 50 times that of Jupiter (0.02 to 0.05 solar masses), it is still too massive to be a planet. As a brown dwarf, its core temperature is high enough to initiate the fusion of deuterium with a proton to form helium-3, but it is thought that it used up all its deuterium fuel long ago. This object now has a surface temperature of 950 K. In March 2014, a super-Neptune mass planet candidate was announced in a much closer-in orbit around GJ 229 (). Given the proximity to the Sun, the orbit of GJ 229b might be fully characterized by the Gaia space-astrometry mission or via direct imaging. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gliese 229」の詳細全文を読む スポンサード リンク
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