APOD090703 近日点与远日点

今天的APOD是太阳，我们平时可能不会注意到，太阳的大小变化有这么大。
http://apod.nasa.gov/apod/ap090703.html

2009 July 3
Perihelion and Aphelion

                               
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Credit & Copyright: Enrique Luque Cervigón
Explanation:
This year Aphelion, the point in Earth's elliptical orbit when it is farthest from the Sun, occurs tomorrow, July 4th. Of course, that doesn't affect the seasons on our fair planet. Those are determined by the tilt of Earth's axis of rotation and not Earth's distance from the Sun, so July is still winter in the south and summer in northern hemisphere. But it does mean that on July 4th the Sun will be at its smallest apparent size. This composite neatly compares two pictures of the Sun taken with the same telescope and camera on the dates of Perihelion (closest approach) and Aphelion in 2008. The image labels include Earth's distance in kilometers from the Sun on the two dates. Otherwise difficult to notice, the change in the Sun's apparent diameter between Perihelion and Aphelion is clear. The difference amounts to a little over 3 percent.

今天的APOD大图，1092X1044
http://apod.nasa.gov/apod/image/0907/PerihelionAphelion_cervignon.jpg

                               
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今天的成大翻译
http://www.phys.ncku.edu.tw/~astrolab/mirrors/apod/apod.html

2009 年 7 月 03 日
近日點與遠日點
影像提供與版權: Enrique Luque Cervigón
說明:
明天(7月4日)地球經過遠日點(Aphelion)，所位的遠日點是指地球公轉太陽時，距離太陽最遙遠的位置。當然日地距離的差異並不影響到地球上季節的更迭，影響地球季節變化的主因是來自於地球自轉軸傾斜，因此七月仍就是北半球夏季、南半球冬季。不過遠日點確實是代表太陽直徑最小。上面這張太陽的合成影像是透過同一組望遠鏡與相機，在2008年的近日點(Perihelion)與遠日點兩天所拍攝，在影像上還標示了當時的日地距離，可明顯的辨識出來，在近日點與遠日點的太陽直徑不同，兩者相差約3%。

还是大图爽！

那谁注意得到啊！