漫遊太陽系(四)
林光餘譯
30. A true color image of Titan's colorful south polar vortex captured by NASA's Cassini spacecraft before a distant flyby of Saturn's moon Titan on June 27, 2012, shows a south polar vortex, or a mass of swirling gas, around the pole in the atmosphere of the moon. The south pole of Titan which is 3,200 miles (5,150 km) across is near the center of the view. The formation of the vortex at Titan's south pole may be related to the coming southern winter and the start of what will be a south polar hood. These new, more detailed images are only possible because of Cassini's newly inclined orbits, which are the next phase of Cassini Solstice Mission.
2012年6月27日，卡西尼太空探測船遠距通過土星的泰坦衛星時，拍攝到泰坦衛星的彩色南極渦流圖。泰坦星南極渦流是一團圍繞泰坦星南極大氣層旋轉的氣團。直徑寬達3,200哩的泰坦星的南極正好位在圖中央。泰坦星南極渦流的構成，可能與即將來臨的南方冬季，以及它的南極冰帽的形成有關。這些新拍攝的照片較之前拍攝的更清晰。可能原因是這時卡西尼探測船正為進行下一階段的「夏至任務」而使運行軌道較前傾斜。(譯註：卡西尼先前飛到土星時正值土星北半球「冬至」。)
31. Saturn's moon Dione, seen before Saturn and part of the rings, on May 02, 2012, from approximately 50,762 miles (81,694 kilometers) away.
2012年5月2日卡西尼探測船所拍攝到的土星衛星「土衛四」以及部分土星環。當時卡西尼探測船距離目標50,762哩(81,694公里) 。
32. A giant of a moon appears before a giant of a planet undergoing seasonal changes in this natural color view of Titan and Saturn from NASA's Cassini spacecraft, on May 6, 2012. As the seasons have changed in the Saturnian system, and spring has come to the north and autumn to the south, the azure blue in the northern Saturnian hemisphere that greeted Cassini upon its arrival in 2004 is now fading. The southern hemisphere, in its approach to winter, is taking on a bluish hue. This change is likely due to the reduced intensity of ultraviolet light and the haze it produces in the hemisphere approaching winter, and the increasing intensity of ultraviolet light and haze production in the hemisphere approaching summer.
2012年5月6日，卡西尼探測船拍攝到巨型行星土星與它的巨型月亮──泰坦衛星的彩色全景季節變化圖。此時春季出現在北半球，秋季出現在南半球。2004年卡西尼探測船到達土星時，北半球氣層所顯現的蔚藍色如今逐漸褪去。南半球則因逐漸接近冬季而轉藍。色彩轉變的可能原因是紫外光密度減低，氣層中因冬季到來而出現霧霾；夏季將至時，色彩則因紫外光密度增加而再次轉變。
33. This image, taken by the Hubble Space Telescope, shows the five known moons orbiting the distant, icy dwarf planet Pluto. The green circle marks the newly discovered moon, designated S/2012 (134340) 1, or P5, as photographed by Hubble's Wide Field Camera 3 on 7 July 2012. The moon is estimated to be 10 to 25 kilometers across. It is in a 95,000 kilometer diameter circular orbit around Pluto that is assumed to be aligned in the same plane as the other satellites in the system. The darker stripe in the center of the image is because the picture is constructed from a long exposure designed to capture the comparatively faint satellites of Nix, Hydra, P4 and S/2012 (134340) 1, and a shorter exposure to capture Pluto and Charon, which are much brighter. NASA's New Horizons probe, which will rendezvous with Pluto in July of 2015, was launched in 2006 -- back then, Pluto only had three known moons.
2012年7月7日，哈伯太空望遠鏡使用3號廣角相機，拍攝這張照片。照片中有五顆已知的冥王星衛星，正在遠距離外繞行冰封的矮行星冥王星。圖中綠圈中心點是一顆新發現的被命名為S/2012(134340)1或P5的冥王星衛星。這顆衛星徑寬約10至25公里。它正以直徑95,000公里的圓周軌道繞行冥王星。推測此衛星與其他冥王星衛星位在同一平面上運行。圖中長條橫紋是長時間曝光所致。長時曝光的目的在於彰顯Nix, Hydra, P4以及S/2012(134340)1等幾顆光線黯淡的衛星；同時以較短時間曝光顯現明亮得多的冥王星與凱倫衛星(冥衛一)。美國太空署在2006年發射的「新視野」探測船，預定於2015年7月與冥王星相會；當年發射時，冥王星只有三顆衛星被發現。