Abell 3827：食人星团引力透镜
(原标题: Abell 3827: Cannibal Cluster Gravitational Lens)
2021-08-23
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是一个星系还是三个？在哈勃拍摄的大质量星系团Abell 3827的特色图像的右侧，是一个看起来最不寻常的星系——弯曲的，有三个中心。然而，一项详细的分析发现，这是同一背景星系的三张照片，而且至少还有四张照片。我们从单一背景蓝色星系看到的光在星团复杂的引力作用下有多条路径，就像一束遥远的光在穿过酒杯的时候有多条路径一样。研究像Abell 3827这样的星团及其组成星系如何偏转远处的光，可以提供有关质量和暗物质分布的信息。Abell 3827非常遥远，红移为0.1，我们看到的光大约是13亿年前发出的——在恐龙漫游地球之前。因此，星系团的中心星系现在肯定都合并了——在一场星系同类相食的盛宴中——在星系团中心附近形成一个巨大的星系。
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Is that one galaxy or three? Toward the right of the featured Hubble image of the massive galaxy cluster Abell 3827 is what appears to be a most unusual galaxy -- curved and with three centers. A detailed analysis, however, finds that these are three images of the same background galaxy -- and that there are at least four more images. Light we see from the single background blue galaxy takes multiple paths through the complex gravity of the cluster, just like a single distant light can take multiple paths through the stem of a wine glass. Studying how clusters like Abell 3827 and their component galaxies deflect distant light gives information about how mass and dark matter are distributed. Abell 3827 is so distant, having a redshift of 0.1, that the light we see from it left about 1.3 billion years ago -- before dinosaurs roamed the Earth. Therefore, the cluster's central galaxies have now surely all coalesced -- in a feast of galactic cannibalism -- into one huge galaxy near the cluster's center.