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APOD090930：土星过春分点

发表于 2009-9-30 12:36 | 查看: 2319| 回复: 12来自：浙江省宁波市电信

明天起可能短期内不关注论坛了，这是今天的APOD
http://apod.nasa.gov/apod/ap090930.html

2009 September 30
Saturn at Equinox

Credit: Cassini Imaging Team,ISS,JPL,ESA,NASA
Explanation:
How would Saturn look if its ring plane pointed right at the Sun?Before last month, nobody knew. Every 15 years, as seen from Earth,Saturn's ringspoint toward the Earth andappear to disappear.The disappearing rings are no longer a mystery -- Saturn's rings are known to beso thin and theEarth is so near the Sunthat when the rings point toward the Sun, they also pointnearly edge-on at the Earth.Fortunately, in thisthird millennium, humanity is advanced enough to have a spacecraft that can see the ringsduring equinoxfrom the side.Last month, that Saturn-orbiting spacecraft,Cassini,was able to snap a series of unprecedented pictures ofSaturn's rings during equinox.A digital composite of 75 such images isshown above.The rings appear unusually dark, and a very thin ring shadow line can be made out on Saturn's cloud-tops. Objects sticking out of the ring plane arebrightly illuminated and castlong shadows. Inspection of these images may helphumanity understand the specificsizes of Saturn's ring particles and thegeneral dynamicsof orbital motion.

土星, 春分点

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购买望远镜就在牧夫天文商城

gohomeman1

发表于 2009-9-30 12:38 来自：浙江省宁波市电信

北京天文馆今天翻译极快，这就是了 http://www.bjp.org.cn/apod/today.htm

春分中的土星

影像提供：Cassini Imaging Team, ISS, JPL, ESA, NASA
说明：
当土星的光环盘面正对着太阳时，看起来是什么样子的？在上月前，没有人知道。从地球看去，每15年土星的光环都将指向地球一次，并且消失。消失的光环不再神秘，土星的光环太稀薄，而地球距离太阳太近，以至于光环指向太阳时，光环同样也近似侧面指向地球。幸运的是，在这第三个世纪里，人类利用足够先进的飞船在春分日里能从侧面看到光环。上月，绕土星飞行的卡西尼飞船，拍摄了一系列春分日土星光环影像。一张由75帧影像合成的数码照片就显示在上面。光环看起来异常昏暗，在土星的云端外还有一道很细的阴影线。伸出光环盘面外的天体被照亮，并投射出长长的阴影。通过仔细检查这些影像能够帮助人类理解土星光环内微粒的特殊大小以及轨道运行的大体动态。

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gohomeman1

发表于 2009-9-30 12:39 来自：浙江省宁波市电信

今天的APOD巨图，为了方便大家下载浏览，我使用的是北京天文馆镜像，7227X3847px。
http://www.bjp.org.cn/files/2009-09/30/F_2d3abecbb0b84749a6aa5345665a9d6d_saturnequinox_cassini_big.jpg

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新地平线号

发表于 2009-9-30 12:41 来自：山东省潍坊市奎文区教育网

真清楚啊

（等你回来啊！）

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gohomeman1

发表于 2009-9-30 12:42 来自：浙江省宁波市电信

几个缩写的翻译：
Cassini Imaging Team：卡西尼（探测器）图像团队

ISS：国际空间站

JPL：美国喷气推进实验室

ESA：欧洲空间局

NASA：美国国家航空航天局/美国宇航局

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gohomeman1

发表于 2009-9-30 12:45 来自：浙江省宁波市电信

当真正环面以侧边面对太阳时，光环会显得更暗。

当然，这种现象已经发生过n次了，说发生时无人知道云云，这是英语的常用说法，大家别当真。

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大眼小蛙

发表于 2009-9-30 13:36 来自：江苏省徐州市电信

近几年不好观测光环，实在是遗憾啊……

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q5968661

发表于 2009-9-30 14:19 来自：福建省厦门市电信

本帖最后由 q5968661 于 2009-9-30 15:54 编辑

this third millennium 这第三个世纪？

2001 January 1

The Millennium that Defines Universe
Credit: Camille Flammarion; Courtesy: HSC, U. Oklahoma;
Digitization: K. Magruder (OU); Coloring: R. J. Nemiroff (Michigan Tech)

Explanation: Welcome to millennium three. During millennium two, humanity continually redefined its concept of "Universe": first as spheres centered on the Earth, in mid-millennium as the Solar System, a few centuries ago as the Galaxy, and within the last century as the matter emanating from the Big Bang. During millennium three humanity may hope to discover alien life, to understand the geometry and composition of our present concept of Universe, and even to travel through this Universe. Whatever our accomplishments, humanity will surely find adventure and discovery in the space above and beyond, and possibly define the surrounding Universe in ways and colors we cannot yet imagine by the threshold of millennium four.