|
Alpha Aquarii (Alpha Aqr, α Aquarii, α Aqr) is a single star in the Aquarius. It has the traditional name Sadalmelik, which is derived from Arabic for "Luck of the king". The apparent visual magnitude of 2.94〔 makes this the second-brightest star in Aquarius. Based upon parallax measurements made during the Hipparcos mission, this star is located at a distance of roughly from Earth.〔 With an age of 53 million years,〔 this star has evolved into a supergiant with a stellar classification of G2 Ib.〔 It has 6.5〔 as much mass as the Sun and has expanded to around 77〔 times the Sun's radius. It is radiating 3,000〔 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 5,210 K.〔 At this heat, the star glows with the yellow hue of a G-type star.〔 Examination of this star with the Chandra X-ray Observatory shows it to be significantly X-ray deficient compared to G-type main sequence stars. This deficit is a common feature of early G-type giant stars.〔 Sadalmelik has a visual companion, designated ''CCDM J22058-0019B'', with an apparent visual magnitude of approximately 12.2. It is at an angular separation of 110.4 arcseconds from Sadalmelik along a position angle of 40°.〔 The name ''Sadalmelik'' derives from an Arabic expression سعد الملك ''sa‘d al-malik'' meaning "Luck of the king". Ulug Beg was combined the name with ο Aqr. The name ''Rucbah'' has also been applied to this star; it shares this name with Delta Cassiopeiae.〔pp. 51, 148, (''Star-names and Their Meanings'' ), Richard Hinckley Allen, New York: G. E. Stechert, 1899.〕 It is only one of two stars with ancient proper names to lie within a degree of the celestial equator. The origin of the Arabic name is lost to history.〔 In Chinese, (), meaning ''Rooftop (asterism)'', refers to an asterism consisting of α Aquarii, θ Pegasi and ε Pegasi.〔 ''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, α Aquarii itself is known as (, (英語:the First Star of Rooftop).)〔 (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.〕 ==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「Alpha Aquarii」の詳細全文を読む スポンサード リンク
|