Arp 194:并合星系群
影像来源与版权:NASA, ESA, Hubble; Judy Schmidt

说明:为什么恒星会在这些碰撞星系之间的星系桥上形成?通常,当星系互相碰撞时,恒星的形成仅限于星系盘或潮汐尾。然而,在星系Arp 194中,年轻恒星的明亮结点正好位于星系连接桥上。对影像(包括这幅由哈勃望远镜拍摄的Arp 194特征影像)和数据进行的分析,以及星系间相互作用的计算机模拟,都表明在过去一亿年中,底部星系正好穿过顶部星系。而残留的一股气体流现在正流向底部星系。天文学家假设,恒星在这座星系桥上形成是因为快速碰撞之后,湍流最近在逐渐减弱。在大约10亿年的时间里,这些星系——包括一个叠加在上层星系上的较小星系(看到了吗?)——将全部合并成一个更大的星系。
翻译:北京天文馆

Arp 194: Merging Galaxy Group
Image Credit: NASA, ESA, Hubble; Processing & License: Judy Schmidt

Explanation: Why are stars forming in the bridge between these colliding galaxies? Usually when galaxies crash, star formation is confined to galaxy disks or tidal tails. In Arp 194, though, there are bright knots of young stars right in a connecting bridge. Analyses of images and data including the featured image of Arp 194 from Hubble, as well as computer simulations of the interaction, indicate that the bottom galaxy passed right through the top galaxy within the past 100 million years. The result has left a stream of gas that is now falling toward the bottom galaxy. Astronomers hypothesize that stars form in this bridge because of the recent fading of turbulence after the rapid collision. In about a billion years, the galaxies — including a smaller galaxy superposed on the upper galaxy (see it?) — will all merge into one larger galaxy.
Astronomy Picture of the Day 03/25/2019