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Zeta Hydrae (ζ Hya, ζ Hydrae) is a solitary star in the equatorial constellation of Hydra. This is a generally faint constellation, so, at an apparent visual magnitude of +3.10,〔 this is the third brightest member after Alphard and Gamma Hydrae. The distance to this star has been measured using the parallax technique, yielding a value of roughly .〔 At this distance, the visual magnitude of the star is diminished by 0.03 as a result of extinction from intervening gas and dust.〔 The star Delta Hydrae is located from Zeta Hydrae and may be a co-moving companion.〔 With a stellar classification of G9 II-III,〔 this is an evolved giant star that is radiating 132〔 times the luminosity of the Sun from its outer envelope at an effective temperature of 4,925 K.〔 At this heat, the star glows with the yellow hue of a G-type star.〔 The radius of this star, as measured using interferometry, is about 18 times the Sun's radius.〔 It has an estimated 4.2 times the mass of the Sun〔 and is around old.〔 ==Name and etymology== This star, along with δ Hya (Lisan al Sudja), ε Hya, η Hya, ρ Hya and σ Hya (Minhar al Shija), were Ulug Beg's Min al Azʽal, "Belonging to the Uninhabited Spot".〔 According to the catalogue of stars in the ''Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars'', ''Min al Azʽal'' or Minazal were the title for five stars:δ Hya as ''Minazal I'', η Hya as ''Minazal II'', ε Hya as ''Minazal III'', ρ Hya as ''Minazal IV'' and ζ Hya as ''Minazal V'' (exclude σ Hya).〔 In Chinese, (), meaning ''Willow'', refers to an asterism consisting of ζ Hydrae, δ Hydra, σ Hydrae, η Hydrae, ρ Hydrae, ε Hydrae, ω Hydrae and θ Hydrae〔 ''中國星座神話'', written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.〕 Consequently, ζ Hydrae itself is known as (, (英語:the Sixth Star of Willow)).〔 (AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 28 日 )〕 The people of Groote Eylandt called Unwala, "The Crab", for the star cluster including this star, δ Hya (Lisan al Sudja), ε Hya, η Hya, ρ Hya and σ Hya (Minhar al Shija).〔 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 Hydrae」の詳細全文を読む スポンサード リンク
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