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Eta Virginis (η Vir, η Virginis) is a multiple star system in the zodiac constellation of Virgo. It has the traditional name Zaniah . From parallax measurements, the distance to this star was found to be roughly . It has an apparent visual magnitude of 3.89,〔 which is bright enough for the system to be seen with the naked eye in dark skies. Although the star looks single, lunar occultations have shown this star to be a very close triple star system consisting of two stars only 0.5 AU apart with a third slightly more distant star. The inner pair is a spectroscopic binary that completes an orbit with a period of 72 days. The inclination of this orbit was determined through interferometer observations to be 45.5°, which allowed the individual masses of the two stars to be estimated. The primary star, η Vir Aa, has a mass of about 2.5 times the Sun's mass, while the secondary, η Vir Ab, has 1.9 solar masses. The faint tertiary star, η Vir B, orbits the inner group in a wider orbit over a period of 13.1 years.〔 Because Zaniah is near the ecliptic, it can be occulted by the Moon and (very rarely) by planets. On October 12, 272 BC, the ancient Greek astronomer Timocharis observed a conjunction of the star with Venus.〔〔 The last occultation by a planet took place on September 27, 1843, also by Venus, which will occult it again on November 19, 2445. ==Etymology== The medieval name Zaniah is from the Arabic زاوية ''zāwiyah'' "corner", the same source as Zavijava. In the catalogue of stars in the ''Calendarium of Al Achsasi Al Mouakket'', this star was designated Thanih al Aoua, which was translated into Latin as Secunda Latratoris, meaning ''the second barker''. This star, along with β Vir (Zavijava), γ Vir (Porrima), δ Vir (Auva) and ε Vir (Vindemiatrix), were Al ʽAwwāʼ, the Barker.〔 In Chinese, (), meaning ''Left Wall of Supreme Palace Enclosure'', refers to an asterism consisting of η Virginis, γ Virginis, δ Virginis, ε Virginis and α Comae Berenices.〔 ''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, η Virginis itself is known as (, (英語:the First Star of Left Wall of Supreme Palace Enclosure).),〔 (香港太空館 - 研究資源 - 亮星中英對照表 ), Hong Kong Space Museum. Accessed on line November 23, 2010.〕 representing (), meaning ''The Left Law Administrator''.〔 (English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name ), Hong Kong Space Museum. Accessed on line November 23, 2010.〕 左執法 (Zuǒzhífǎ), spelled Tso Chih Fa by R.H. Allen, means "the Left-hand Maintainer of Law" 〔(Richard Hinckley Allen: Star Names — Their Lore and Meaning: Virgo )〕 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「Eta Virginis」の詳細全文を読む スポンサード リンク
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