Astronomy Picture of the Day——Arp 194：合并星系群
Discover the cosmos! Each day a differentimage or photograph of our fascinating universe is featured, along with a briefexplanation written by a professional astronomer.
Arp 194: Merging Galaxy Group
Image Credit: NASA, ESA, Hubble; Processing& License: Judy Schmidt
Explanation: Why are stars forming in thebridge between these colliding galaxies? Usually when galaxies crash, starformation is confined to galaxy disks or tidal tails. In Arp 194, though, thereare bright knots of young stars right in a connecting bridge. Analyses ofimages and data including the featured image of Arp 194 from Hubble, as well ascomputer simulations of the interaction, indicate that the bottom galaxy passedright through the top galaxy within the past 100 million years. The result hasleft a stream of gas that is now falling toward the bottom galaxy. Astronomershypothesize that stars form in this bridge because of the recent fading ofturbulence after the rapid collision. In about a billion years, the galaxies --including a smaller galaxy superposed on the upper galaxy (see it?) ——will allmerge into one larger galaxy.
Arp 194：合并星系群
说明：为什么这些碰撞星系之间的星系桥上会形成恒星？通常，星系互相碰撞时，恒星仅形成于星系盘或潮汐尾。然而，在星系Arp 194中，新生恒星明亮的结点恰好位于星系连接桥上。对图片和数据进行的分析，以及星系间相互作用的计算模拟，都表明，在过去的一亿年间，底部星系正好穿过顶部星系。而残留的气体流现在正向底部星系流去。天文学家假设，恒星在这座星系桥上形成是因为星系快速碰撞之后，湍流最近在逐渐减弱。在大约10亿年的时间间，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？右侧）将全部合并成一个更大的星系。
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