Arp 87: 哈勃拍摄的合并中星系对

2023年10月24日

Arp 87: Merging Galaxies from Hubble
Image Credit: NASA, ESA, Hubble; Processing: Harshwardhan Pathak

Explanation: This dance is to the death. As these two large galaxies duel, a cosmic bridge of stars, gas, and dust currently stretches over 75,000 light-years and joins them. The bridge itself is strong evidence that these two immense star systems have passed close to each other and experienced violent tides induced by mutual gravity. As further evidence, the face-on spiral galaxy on the right, also known as NGC 3808A, exhibits many young blue star clusters produced in a burst of star formation. The twisted edge-on spiral on the left (NGC 3808B) seems to be wrapped in the material bridging the galaxies and surrounded by a curious polar ring. Together, the system is known as Arp 87. While such interactions are drawn out over billions of years, repeated close passages will ultimately create one merged galaxy. Although this scenario does look unusual, galactic mergers are thought to be common, with Arp 87 representing a stage in this inevitable process. The Arp 87 dancing pair are about 300 million light-years distant toward the constellation of the Lion (Leo). The prominent edge-on spiral galaxy at the far left appears to be a more distant background galaxy and not involved in the on-going merger.

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Arp 87: 哈勃拍摄的合并中星系对
影像提供: NASA, ESA, Hubble; 影像处理: Harshwardhan Pathak

说明: 这是死亡之舞。在此过程中，随着这二个大星系进行缠斗，一道由恒星、云气和尘埃所构成，绵延超过75,000光年的宇宙桥联结了这对星系。这道宇宙长桥明确地指证，这两个庞大的恒星系统曾近距离通过对方附近，而彼此之间的重力互扰引发了剧烈的潮汐。作为进一度的佐证，影像右侧的正面螺旋星系NGC 3808A，经历了爆发性的恒星形成活动，并产生许多泛蓝的年轻星团。而左方扭曲的侧向星系NGC 3808B，则被星系间的长桥物质及一个很有趣的绕极环所包裹。这个带着Arp 87编号的系统，因其外貌而被归类为特殊天体。这种引力交互作用的历程长达数十亿年，但重复的近距离穿越，最终会让它们合并成单一个星系。虽然这种景象看起来相当奇特，但星系合并咸认是很常见的现象，而Arp 87则代表这种必然过程的中间阶段。Arp 87星系对位在狮子座方向，离我们约有3亿光年远。影像左缘的醒目侧向螺旋星系，是一个更遥远的背景星系，并未参与这场进行中的星系合并。

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