2020 January 8
Galaxies in the River
Image Credit & Copyright: Star Shadows Remote Observatory, PROMPT, CTIO
Explanation: Large galaxies grow by eating small ones. Even our own galaxy engages in a sort of galactic cannibalism, absorbing small galaxies that are too close and are captured by the Milky Way’s gravity. In fact, the practice is common in the universe and illustrated by this striking pair of interacting galaxies from the banks of the southern constellation Eridanus, The River. Located over 50 million light years away, the large, distorted spiral NGC 1532 is seen locked in a gravitational struggle with dwarf galaxy NGC 1531 (right of center), a struggle the smaller galaxy will eventually lose. Seen edge-on, spiral NGC 1532 spans about 100,000 light-years. Nicely detailed in this sharp image, the NGC 1532/1531 pair is thought to be similar to the well-studied system of face-on spiral and small companion known as M51.
说明: 大星系靠吞食小星系来成长。就连我们的银河系，也是星系互食行为的信奉者，靠得太近的小星系，会被银河系的重力捕获然后吞掉。在宇宙中，星系互食的现象非常普遍，上面这对位在南天．波江座方向的星系对就是很好的例证。这对离我们5千多万光年远的星系，较大的扭曲螺旋星系NGC 1532，正透过重力和矮星系NGC 1531（中右方）进行重力缠斗，而对小星系来说，这是一场毫无胜算的战争。侧向着我们的螺旋星系NGC 1532，大小约为100,000光年。这幅高清影像所呈现的NGC 1532/1531星系对，被认为和我们很熟悉的正向螺旋星系对M51很类似。