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Zeta Doradus (ζ Dor) is a young star system that lies approximately 38 light-years away. The system consists of two widely separated stars, with the primary being bright enough to be observed with the naked eye but the secondary being much a much fainter star that requires telescopic equipment to be observed. ==Components== Zeta Doradus A is a bright, high proper motion star with a spectral type of F7V, meaning that it is a main sequence star that is hotter and brighter than the Sun. With an apparent magnitude of 4.82, it is approximately the eight brightest star in the constellation of Dorado. Though it has been known that Zeta Doradus B is a nearby star since at least the Gliese Catalogue of Nearby Stars, the connection that it is a common proper motion companion to Zeta Doradus A was only made much more recently thanks to HIPPARCOS data. The two stars form a wide binary, with a physical separation between the components of about 0.018 parsecs (0.06 light-years) which is approximately 12400 AU.〔 This is comparable to the 15000 AU separation between Alpha Centauri AB and Proxima Centauri. Both components of the system show considerable activity: The log R'HK of the stars are -4.373 and -4.575,〔 respectively, whereas a star is "quiet" when it has a Log R'HK of <-4.8. This indicates that the system is young; indeed, the estimated age for Zeta Doradus A is only 0.58 Gigayears,〔 about an eighth of the solar age. It is not unusual for a young star to possess a debris disk; Zeta Doradus A is no exception, as it has been found to have an infra-red excess indicative of a disk of small bodies like comets re-emitting absorbed light at a redder wavelength. For Zeta Doradus A, the dust disk has a luminosity of 6.0 x 10−6 times the solar luminosity〔 and a temperature of 91 ± 12 Kelvin,〔 indicating that it lies at a separation of several AU. 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「Zeta Doradus」の詳細全文を読む スポンサード リンク
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