本帖最后由 gohomeman1 于 2009-3-18 10:50 编辑
March 17, 2009 09:00 AM (EDT)
News Release Number: STScI-2009-12
Quadruple Saturn Moon Transit Snapped by Hubble
ABOUT THIS IMAGE:
On February 24, 2009,the Hubble Space Telescope took a photo of four moons of Saturn passingin front of their parent planet. In this view, the giant orange moon Titan casts a large shadow onto Saturn's north polar hood. Below Titan,near the ring plane and to the left is the moon Mimas, casting a muchs maller shadow onto Saturn's equatorial cloud tops. Farther to the left, and off Saturn's disk, are the bright moon Dione and the fainter moon Enceladus.
2009.2.24，哈勃太空望远镜获得了一系列图片，图片显示土星的四个小卫星在土星行星背景前列队而过。在土星北极附近投下的巨大阴影的橙色大卫星是土卫六——泰坦。泰坦左下靠近土星光环的是土卫一弥玛斯，在土星赤道云层上投下小得多的投影。更远的左边的土星环上方，是明亮的土卫四狄俄涅和昏暗的土卫二恩克拉多斯(土星的卫星基本都是神话中的巨人啊，本文说的就是这4个卫星，注意后面的图上的黑点是阴影)。
These rare moon transits only happen when the tilt of Saturn's ring plane is nearly "edge on" as seen from the Earth. Saturn's rings will be perfectly edge on to our line of sight on August 10, 2009, and September 4, 2009. Unfortunately, Saturn will be too close to the sun to be seen by viewers on Earth at that time. This "ring plane crossing" occurs every 14-15 years. In 1995-96 Hubble witnessed the ring plane crossing event, as well as many moon transits, and even helped discovers everal new moons of Saturn.
这种卫星横越土星表面的现象只发生在土星光环面与我们的视线基本平行的时候（“倾角”接近0）。2009.8.10和2009.9.4，光环倾角将完美的趋向0.但不幸的是，这时土星与太阳在天空中的位置太接近了，从我们地球很难观察它。“土星光环线性化”每隔14-15年发生一次。1995-96年期间，哈勃目击了土星环线性化事件，那次也观察到大量卫星从土星面前经过事件，（这）有助于发现新的土星卫星。
PS：我不知道土星光环缩小到一条线这件事在天文学上怎么称呼，大家明白这个意思就是。此时用小望远镜已经看不见光环。
The banded structure in Saturn's atmosphere is similar to Jupiter's.
Early 2009 was a favorable time for viewers with small telescopes towatch moon and shadow transits crossing the face of Saturn. Titan,Saturn's largest moon, crossed Saturn on four separate occasions:January 24, February 9, February 24, and March 12, although not all events were visible from all locations on Earth.
土星大气的条纹结构与木星的类似。
2009年上半年是小望远镜观察土卫们和它们的影子在土星前面穿过的好时机。土星最大的卫星——土卫六在以下4个时间从土星前面经过：1.24，2.9，2.24，3.12，虽然地球上的观察者不能在这四次时间都看见这个事件（有可能在白天——译注）。
These pictures were taken with Hubble's Wide Field Planetary Camera2 on February 24, 2009, when Saturn was at a distance of roughly 775million miles (1.25 billion kilometers) from Earth. Hubble can see details as small as 190 miles (300 km) across on Saturn. The dark band running across the face of the planet slightly above the rings is the shadow of the rings cast on the planet.
这些图片是哈勃在2009.2.24用广角行星相机2拍摄的（貌似现在哈勃唯一可用的就是这个相机了——译注）。此时土星离我们约12.5亿公里，WFPC2的分辨率是土星上300千米大小的细节。光环上方土星表面上的黑色细带是光环的影子。
Object Name: Saturn
Image Type: Astronomical
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) |
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置顶卡
变色卡
千斤顶
显身卡