土卫四和土卫五环凌日
(原标题: Dione and Rhea Ring Transit)
2025-11-22
浏览次数: 1504
在这张清晰的望远镜快照中，在土星带状行星盘的左边，有两颗冰冷的小卫星土卫四和土卫五从这颗气体巨星广阔的环系统前面经过。这张引人注目的照片是在11月20日拍摄的，当时从地球上看，土星的光环几乎是侧面的。事实上，每隔13到16年，从地球上看到的景象就会与土星的环面对齐，从而产生一系列的环面交叉。在环平面穿越时，行星际的边缘透视使得薄而明亮的环似乎消失了。到11月23日，土星环将达到目前的最小角度，即从地球上观测时最窄的角度，但随后又开始变宽。当然，土卫四和土卫五在土星环平面附近分别每2.7天和4.5天绕土星运行一次，而从地球上看到的下一系列土星环平面交叉将在2038年开始。
查看原文解释
Seen to the left of Saturn's banded planetary disk, small icy moons Dione and Rhea are caught passing in front of the gas giant's extensive ring system in this sharp telescopic snapshot. The remarkable image was recorded on November 20, when Saturn's rings were nearly edge-on when viewed from planet Earth. In fact, every 13 to 16 years the view from planet Earth aligns with Saturn's ring plane to produce a series of ring plane crossings. During a ring plane crossing, the interplanetary edge-on perspective makes the thin but otherwise bright rings seem to disappear. By November 23rd Saturn's rings will have reached a minimum angle for now, at their narrowest for viewing from planet Earth, but then start to widen again. Of course, Dione and Rhea orbit Saturn near the ring plane once every 2.7 and 4.5 days respectively, while the next series of Saturn ring plane crossings as seen from Earth will begin again in 2038.
© Christopher Go