CG 4 ：星團與星系
CG 4: The Globule and the Galaxy
來源：William Vrbasso｜發表日期：2026-03-11
這難道是準備吞噬毫無防備的星系的宇宙怪獸？所幸並非如此。主圖中這團紅色"怪獸"實為彗星狀星雲CG 4 ，位於船尾座，距離地球 1300 光年。CG 4 是一片分子云，其中氫氣冷卻至足以形成分子，這些分子在引力作用下聚合形成恆星。 CG 4 的形態酷似彗星，其星核直徑達 1 . 5 光年，彗尾綿延 8 光年之長——作為參照，地球到太陽的距離僅為 8 光分。天文學家認為，彗狀球狀體的彗尾可能由鄰近超新星爆發或高溫大質量恆星的輻射所塑造。 事實上，CG 4 及其他鄰近球狀體均指向遠離帆船座超新星殘骸的方向——該殘骸位於甘姆星雲中心。而側面朝向的螺旋星系ESO 257 - 19 位於CG 4 百餘萬光年之外，完全不受這頭"怪物"的威脅。
原文：Is this a cosmic monster ready to devour an unsuspecting galaxy? Thankfully, that is not the case. The red “monster” shown in the featured image is Cometary Globule CG 4, 1,300 light-years away in the Constellation Puppis. CG 4 is a molecular cloud, where hydrogen becomes cold enough to form molecules that can be brought together by gravity to create stars. The shape of CG 4 resembles that of a comet, but its head is 1.5 light-year in diameter and its tail is 8 light-years long; for comparison, the distance from the Earth to the sun is only 8 light-minutes. Astronomers believe that the tail of a cometary globule could have been shaped by a nearby supernova explosion or by irradiation from hot, massive stars. Indeed, CG 4 and other nearby globules point away from the Vela Supernova Remnant, at the center of the Gum Nebula. The edge-on spiral galaxy, ESO 257-19, is more than a hundred million light-years beyond CG 4, and is completely safe from the “monster”.
※ 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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