研究人员从斯隆数字巡天计划中搜集了 8000 个星系团的数据，他们通过平均这些数据处理了这个问题。

The researchers approached the problem by averaging data collected from 8000 galaxy clusters by the Sloan Digital Sky Survey.

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该图来自斯隆数字巡天计划，可以看出那些小行星（画绿圈圈的）在移动，而右下方的NGC4517A星系就很呆。

In images from the Sloan Digital Sky Survey, asteroids (circled in green) appear to move over time. Galaxies like NGC4517A, at lower right, don't.

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