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One of the most important was done by the astronomer George Abell. Abell completed his survey in 1958.
最重要的调查之一是由天文学家George Abell完成的。Abell在1958年完成了他的调查。
It added considerably to the map made by Shapley and Ames. In fact, his map had over 2700 clusters of galaxies.
它对Shapley和Ames制作的地图进行了大量补充。事实上，他的地图上有超过2700个星团。
That's 2700 clusters of galaxies! Not just galaxies.
那可是2700个星团啊！不只是星系。
But there’s another aspect of Abell’s work that makes this map so valuable to astronomers.
但是使得Abell完成这个地图的成果对天文学家来说如此宝贵的还有另一个方面。
He introduced a classification scheme for the galaxy clusters.
他提出了星团的一个分类体制。
Now, surveys completed since Abell’s have catalogued additional galaxies and surveyed more outer space, but no one has improved upon Abell’s classification scheme.
自Abell之后完成的研究编录了额外的星系，并且探测了更外层的太空，但是没人能对Abell的分类体制加以改进。
In fact, the Abell catalogue is used as a starting point for astronomers who study these objects.
事实上，Abell的编录被研究这些物体的天文学家用作了一个起始点。
One of the reasons his scheme has been so widely accepted is because of his sample size.
他的体制被如此广泛接受的原因之一是因为他的取样规模。
With all the clusters in his sample, he could determine the different characteristics of clusters.
借助样品中所有的星团，他能确定这些星团之间不同的特征。
And these characteristics form the basis of his classification scheme.
而这些特征形成了他的分类体制的基础。
Now, two of the characteristics crucial to his classification were richness and symmetry.
对他的分类至关重要的两个特征是丰富程度和对称性。
So what did he mean by richness? Well, basically it refers to the number of galaxies there are within a cluster.
那么丰富程度是什么意思呢？它主要是指一个星团内的星系数量。
