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36 Ursae Majoris is a double star〔 in the northern constellation of Ursa Major. With an apparent visual magnitude of 4.82,〔 it can be seen with the naked eye in suitable dark skies. Based upon parallax measurements, this star lies at a distance of from Earth.〔 This star is a solar analog—meaning it has physical properties that make it similar to the Sun. It has 12% more mass and a radius 15% larger than the Sun,〔 with an estimated age of 2.7 billion years.〔 The spectrum of this star matches a stellar classification of F8 V, which indicates this is a main sequence star that is generating energy at its core through the nuclear fusion of hydrogen. The energy is being radiated into space from its outer envelope at an effective temperature of 6,126 K.〔 This gives the star the characteristic yellow-white hue of an F-type star.〔 36 Ursae Majoris has a magnitude 8.86 common proper motion companion with about half this star's mass〔 at an angular separation of 122.5″ along a position angle of 303°, as of 2012. A second companion with a magnitude of 11.44 is located at an angular separation of 240.6″ along a position angle of 292°, as of 2004.〔 == Hunt for substellar objects == According to Nelson & Angel (1998),〔(The Range of Masses and Periods Explored by Radial Velocity Searches for Planetary Companions )〕 36 Ursae Majoris could host one or two (or at least three) jovian planets (or even brown dwarfs) at wide separations from the host star, with orbital periods of 10–15, 25 and 50 years respectively. The authors have set upper limits of 1.1–2, 5.3 and 24 Jupiter masses for the putative planetary objects. Also Lippincott (1983)〔(An unseen companion to 36 Ursae Majoris A from analysis of plates taken with the Sproul 61-CM refractor )〕 had previously noticed the possible presence of a massive unseen companion (with nearly 70 times the mass of Jupiter, just below the stellar regime, thus a brown dwarf). Putative parameters for the substellar object show an orbital period of 18 years and quite a high eccentricity (e=0.8). Even Campbell et al. 1988〔(A search for substellar companions to southern solar-type stars )〕 inferred the existence of planetary objects or even brown dwarfs less massive than 14 Jupiter masses around 36 Ursae Majoris. Nevertheless, no certain planetary companion has yet been detected or confirmed. The McDonald Observatory team has set limits to the presence of one or more planets〔( Detection Limits from the McDonald Observatory Planet Search Program )〕 with masses between 0.13 and 2.5 Jupiter masses and average separations spanning between 0.05 and 5.2 AU. An infrared excess has been detected around this star, most likely indicating the presence of a circumstellar disk at a radius of 38.6 AU. The temperature of this dust is 50 K.〔 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「36 Ursae Majoris」の詳細全文を読む スポンサード リンク
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