狄奧與瑞亞環過境
Dione and Rhea Ring Transit
來源：Christopher Go｜發表日期：2025-11-22
在這張清晰的望遠鏡快照中，土星帶狀行星盤左側的小冰衛星狄奧（Dione）和瑞亞（Rhea）從這顆氣體巨行星龐大的星環系統前掠過。這幅照片拍攝於 11 月 20 日，當時從地球上看土星環幾乎處於邊緣位置。事實上，每隔 13 到 16 年，從地球上看土星環的視線就會與土星環的環面對齊，從而產生一系列環面交叉。在環平面交叉期間，行星際邊緣視角會使薄而明亮的星環似乎消失。到 11 月 23 日，土星環將達到目前的最小角度，也就是從地球上看土星環最窄的角度，但隨後又開始變寬。當然，狄奧和瑞亞分別每 2 . 7 天和 4 . 5 天在環面附近繞土星執行一次，而從地球上看到的下一輪土星環面穿越將在 2038 年再次開始。
原文：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.
※ 本文由萌芽機器人自動轉貼自每日一天文圖（Astronomy Picture of the Day，APOD），原文為英文，正體中文是透過 DeepL 翻譯及 OpenCC 進行自動處理，內容僅供參考，若有任何錯誤之處還請見諒！
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