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One of the most important was done by the astronomer George Abell. Abell completed his survey in 1958.
最重要的調(diào)查之一是由天文學家George Abell完成的。Abell在1958年完成了他的調(diào)查。
It added considerably to the map made by Shapley and Ames. In fact, his map had over 2700 clusters of galaxies.
它對Shapley和Ames制作的地圖進行了大量補充。事實上，他的地圖上有超過2700個星團。
That's 2700 clusters of galaxies! Not just galaxies.
那可是2700個星團啊！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完成這個地圖的成果對天文學家來說如此寶貴的還有另一個方面。
He introduced a classification scheme for the galaxy clusters.
他提出了星團的一個分類體制。
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之后完成的研究編錄了額外的星系，并且探測了更外層的太空，但是沒人能對Abell的分類體制加以改進。
In fact, the Abell catalogue is used as a starting point for astronomers who study these objects.
事實上，Abell的編錄被研究這些物體的天文學家用作了一個起始點。
One of the reasons his scheme has been so widely accepted is because of his sample size.
他的體制被如此廣泛接受的原因之一是因為他的取樣規(guī)模。
With all the clusters in his sample, he could determine the different characteristics of clusters.
借助樣品中所有的星團，他能確定這些星團之間不同的特征。
And these characteristics form the basis of his classification scheme.
而這些特征形成了他的分類體制的基礎。
Now, two of the characteristics crucial to his classification were richness and symmetry.
對他的分類至關重要的兩個特征是豐富程度和對稱性。
So what did he mean by richness? Well, basically it refers to the number of galaxies there are within a cluster.
那么豐富程度是什么意思呢？它主要是指一個星團內(nèi)的星系數(shù)量。
