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HD 40307 f is an extrasolar planet orbiting the star HD 40307. It is located 42 light-years away in the direction of the southern constellation Pictor. The planet was discovered by the radial velocity method, using the European Southern Obervatory's HARPS apparatus by a team of astronomers led by Mikko Tuomi at the University of Hertfordshire and Guillem Anglada-Escude of the University of Goettingen, Germany. This planet is the fifth planet from the star, at a distance of about 0.25 AU (compared to 0.39 AU for Mercury) with negligible eccentricity. HD 40307 f's minimum mass is 5.2 that of Earth, and dynamical models suggest it cannot be much more (and so is measured close to edge-on).〔 Planets like this in that system have been presumed "super-Earth". Even though HD 40307 f is closer to the star than Mercury is to the Sun, it gets (slightly) less insolation than Mercury gets because the parent star is dimmer than our home star.〔Tuomi, Fig 17〕 It still gets more heat than Venus gets (like Gliese 581 c), and it has more gravitational potential than Venus has. HD 40307 f is more likely a super-Venus than a "super-Earth".〔Tuomi, Fig 17 cites Fig 4 in , "100% clouds" region〕 Moreover planets b, c, and d are presumed to have migrated in from outer orbits; and planet b is predicted a sub-Neptune. It is likely that this planet f formed even further out. Whether it is a sub-Neptune or super-Venus is, perhaps, a moot point. ==References== 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「HD 40307 f」の詳細全文を読む スポンサード リンク
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