軌道交點
軌道交點是傾斜的軌道穿越參考平面的兩個點之一[1]。包含於參考平面上的軌道(稱為無傾斜軌道)沒有交點。一般的參考平面有:
- 對地心軌道的參考平面是地球的赤道平面。在這種情況的無傾斜軌道稱為赤道面[2]。
- 對日心軌道的參考平面是黃道。在這種情況的無傾斜軌道稱為黃道面[2]。
- 對太陽系之外的軌道,參考平面是垂直於觀測者視線方向的平面,稱為天球平面[3], chap. 17.。
交線是天體的軌道平面與參考平面交會之間的交集,它經過這兩個交點[2]。
如果參考平面的參考方向被定義在其中的一個平面側,則這兩個交點就可以被區分。對地心和日心軌道,稱為升交點(或北交點)的是軌道上的天體運行到參考平面北側時通過點,而降交點(或南交點)則是天體運行至南側時通過的點[4]。對於太陽系之外的軌道,升交點是天體遠離觀測者時所經過的點,降交點則是朝向觀測者接近時所經過的點[5], p. 137.。
升交點的符號是(Unicode: U+260A, ☊),而降交點的符號是(Unicode: U+260B, ☋)。在中世紀與現代的早期,升交點和降交點分別被稱為龍頭(拉丁:龍骨,阿拉伯:ra's al-jauzahar)和龍尾(拉丁語:)相對應[6], p. 141; [7], p. 245.。同樣的,在阿拉伯語中如ganzaar、genzahar、geuzaar和zeuzahar等已經很少用到的字,都曾被中世紀的西方用來表示這兩個交點[8], pp. 196–197; [9], p. 65; [10], pp. 95–96.。希臘的名詞αναβιβάζων和καταβιβάζων也被用來稱呼升交點和降交點,在英文以anabibazon和catabibazon表示升交點[11]; [12], ¶27.。
參考資料
- node 的存檔,存档日期2007-03-09., entry in The Columbia Encyclopedia, 6th ed., New York: Columbia University Press, 2001–04. Accessed on line May 17, 2007.
- line of nodes 页面存档备份,存于, entry in The Encyclopedia of Astrobiology, Astronomy, and Spaceflight, David Darling, on line, accessed May 17, 2007.
- Celestial Mechanics 页面存档备份,存于, Jeremy B. Tatum, on line, accessed May 17, 2007.
- ascending node 页面存档备份,存于, entry in The Encyclopedia of Astrobiology, Astronomy, and Spaceflight, David Darling, on line, accessed May 17, 2007.
- The Binary Stars, R. G. Aitken, New York: Semi-Centennial Publications of the University of California, 1918.
- Survey of Islamic Astronomical Tables, E. S. Kennedy , Transactions of the American Philosophical Society, new series, 46, #2 (1956), pp. 123–177.
- Cyclopædia, or, An universal dictionary of arts and sciences 页面存档备份,存于, Ephraim Chambers, London: Printed for J. and J. Knapton [and 18 others], 1728, vol. 1.
- Planetary Latitudes, the Theorica Gerardi, and Regiomontanus, Claudia Kren, Isis, 68, #2 (June 1977), pp. 194–205.
- Prophatius Judaeus and the Medieval Astronomical Tables, Richard I. Harper, Isis 62, #1(Spring, 1971), pp. 61–68.
- Lexicographical Gleanings from the Philobiblon of Richard de Bury, Andrew F. West, Transactions of the American Philological Association(1869-1896), 22(1891), pp. 93–104.
- anabibazon, entry in Webster's third new international dictionary of the English language unabridged: with seven language dictionary, Chicago: Encyclopaedia Britannica, 1986. ISBN 0-85229-503-0.
- New thoughts on the genesis of the mysteries of Mithras, Roger Beck, Topoi 11, #1 (2001), pp. 59–76.
- Introduction to Astronomy 250, Coordinates, Seasons, Eclipses 页面存档备份,存于, lecture notes, Astronomy 250, Marcia Rieke, University of Arizona, accessed on line May 17, 2007.
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