Distribution Of Galaxies托福聽力原文翻譯及問題答案

Distribution Of Galaxies托福聽力原文翻譯及問題答案

一、Distribution Of Galaxies 托福聽力原文：

NARRATOR: Listen to part of a lecture in an astronomy class.

MALE PROFESSOR: Before we continue talking about the properties of individual galaxies, it's worth talking about the distribution of galaxies in space. Efforts at mapping, or surveying the universe, uh, making a sort of atlas of galaxies, have been going on for more than fifty years—and, um, the creators of the first major map of the universe were the astronomers Harlow Shapley and Adelaide Ames.

In 1932, Shapley and Ames catalogued the positions of 1,250 galaxies by photographing what they saw through their telescopes.

And they made an important discovery. Their survey was the first to indicate that galaxies were not distributed uniformly in space. Some areas had a lot of galaxies, and other areas had just a few. Uh, another way of putting this is to say that galaxies are clustered. They're not spread evenly throughout the universe. So we have stars grouped together in galaxies, and galaxies grouped together in clusters. OK?

Now, uh, after their survey, other astronomers completed surveys that added to the number of clusters catalogued.

One of the most important was done by the astronomer George Abell. Abell completed his survey in 1958. It added considerably to the map made by Shapley and Ames. In fact, his map had over 2,700 clusters of galaxies, that's 2,700 clusters of galaxies, not just galaxies.

But there's another aspect of Abell's work that makes this map so valuable to astronomers. He introduced a classification scheme for the galaxy clusters. Now, uh, surveys completed since Abell's have catalogued additional galaxies and surveyed more of outer space, but no one has improved upon Abell's classification scheme. In fact, the Abell catalogue is used as a starting point for astronomers who study these objects.

One of the reasons his scheme has been so widely accepted is because of his sample size. With all the clusters in his sample, he could determine the different characteristics of clusters. And these characteristics formed the basis of his classification scheme. Now, two of the characteristics crucial to his classification were richness and symmetry. So, ah, what did he mean by richness?

Well, basically it refers to the number of galaxies there are within a cluster.

FEMALE STUDENT: Is that the same as density?

MALE PROFESSOR: That’s right. Both, uh, “richness” and “density” refer to the number per area. Rich clusters, or dense clusters, uh, contain a relatively high number of galaxies.

FEMALE STUDENT: And symmetry just refers to its shape?

MALE PROFESSOR: Mm, roughly speaking, yes. Uh, whether the shape of the cluster was the same on the left side as on the right side.

So Abell used categories like that to classify clusters on a scale, from regular to irregular.

A “regular” cluster is sphere-shaped, symmetrical, and most dense in the middle, uh, with the greatest number of galaxies concentrated in the middle of the cluster.

An “irregular” cluster might appear to be lopsided, asymmetrical, with a low concentration of galaxies in the center.

FEMALE STUDENT: You're talking about the shape of the cluster though, not the shape of the galaxies within the cluster.

MALE PROFESSOR: Right. Uh, for example, let's consider the Coma cluster. It's a symmetrical cluster, basically spherical in shape. But the individual galaxies within it are elliptical. They're not spherical or spiral shaped. But the cluster itself shows spherical symmetry.

Um, the Virgo cluster, on the other hand, is considered irregular; there's no symmetry to its overall shape, no central concentration of galaxies. But it happens to have both elliptical and spiral galaxies within it.

FEMALE STUDENT: Another question—you were saying how some clusters have more galaxies than others—how many galaxies does a cluster have to have in order to even be a cluster?

MALE PROFESSOR: Good question.

Abell’s definition of a cluster is this.

First, there have to be more than fifty galaxies within a specific amount of space. He said basically that clusters have a radius of roughly 2 megaparsecs. And it was just an assumption, that all clusters would be about the same size. It's remarkable that it proved to be correct. And this “standard” cluster radius is known today as the Abell radius.

And second, those fifty-plus galaxies have to be a certain brightness. Of course, it was a rough estimate, but looking at galaxies' brightness was a good way to distinguish between clusters that were nearby and those that were more distant.

二、Distribution Of Galaxies 托福聽力中文翻譯：

旁白：在天文學課上聽一節(jié)課的一部分。

男教授：在我們繼續(xù)討論單個星系的特性之前，有必要先討論一下星系在空間中的分布。測繪或測量宇宙的努力，呃，制作一種星系地圖冊，已經(jīng)進行了五十多年，第一張主要的宇宙地圖的創(chuàng)造者是天文學家哈洛·夏普利和阿德萊德·艾姆斯。

1932年，Shapley和Ames通過拍攝他們通過望遠鏡看到的東西，對1250個星系的位置進行了編目。

他們有了一個重要的發(fā)現(xiàn)。他們的調(diào)查首次表明星系在空間中的分布并不均勻。一些區(qū)域有很多星系，而其他區(qū)域只有少數(shù)。呃，另一種說法是星系是集群的。它們并沒有均勻地分布在整個宇宙中。所以我們有恒星在星系中聚集在一起，星系在星系團中聚集在一起。好啊

現(xiàn)在，呃，在他們的調(diào)查之后，其他天文學家完成了調(diào)查，增加了編目星團的數(shù)量。

其中最重要的一項研究是由天文學家喬治·阿貝爾完成的。阿貝爾于1958年完成了他的調(diào)查。這大大增加了Shapley和Ames繪制的地圖。事實上，他的地圖上有2700多個星系團，也就是2700個星系團，不僅僅是星系。

但阿貝爾工作的另一個方面使這張地圖對天文學家如此有價值。他介紹了星系團的分類方案?，F(xiàn)在，呃，自阿貝爾以來完成的調(diào)查已經(jīng)對其他星系進行了編目，并調(diào)查了更多的外層空間，但沒有人對阿貝爾的分類方案進行改進。事實上，阿貝爾目錄是天文學家研究這些天體的起點。

他的方案被廣泛接受的原因之一是他的樣本量。利用樣本中的所有簇，他可以確定簇的不同特征。這些特征構成了他的分類方案的基礎?，F(xiàn)在，對他的分類至關重要的兩個特征是豐富性和對稱性。那么，啊，他所說的富裕是什么意思？

基本上它指的是星系團中星系的數(shù)量。

女學生：這和密度一樣嗎？

男教授：沒錯?！柏S富度”和“密度”都是指每個區(qū)域的數(shù)量。富星系團或致密星系團，呃，包含相對較多的星系。

女學生：對稱就是指它的形狀？

男教授：嗯，粗略地說，是的。呃，集群的形狀在左側(cè)和右側(cè)是否相同。

所以Abell用這樣的分類來對集群進行分類，從規(guī)則到不規(guī)則。

一個“規(guī)則”星系團是球狀的，對稱的，最密集的在中間，呃，最大數(shù)量的星系集中在星系團的中間。

一個“不規(guī)則”星系團可能看起來是不平衡的、不對稱的，中心星系的濃度很低。

女學生：你說的是星系團的形狀，而不是星系團中星系的形狀。

男教授：對。呃，舉個例子，讓我們考慮一下昏迷團。它是一個對稱的星團，基本上呈球形。但其中的單個星系是橢圓形的。它們不是球形或螺旋形的。但星團本身表現(xiàn)出球面對稱性。

嗯，另一方面，室女座星團被認為是不規(guī)則的；它的整體形狀沒有對稱性，沒有集中的星系。但它碰巧有橢圓星系和旋渦星系。

女學生：另一個問題，你說的是為什么有些星系團比其他星系團有更多的星系，一個星系團要成為一個星系團，必須有多少個星系？

男教授：好問題。

Abell對集群的定義是這樣的。

首先，在一定的空間范圍內(nèi)，必須有50多個星系。他說，基本上，集群的半徑約為2兆帕斯卡。這只是一個假設，所有集群的大小都差不多。值得注意的是，它被證明是正確的。這個“標準”星團半徑今天被稱為阿貝爾半徑。

其次，這五十多個星系必須有一定的亮度。當然，這是一個粗略的估計，但觀察星系的亮度是區(qū)分附近星系團和較遠星系團的一個好方法。

三、Distribution Of Galaxies 托福聽力問題：

Q1:1.What is the main purpose of the lecture?

A. To explain the difficulty of classifying distant objects in the universe?

B. To introduce a classification system for galaxy clusters?

C. To present some recent discoveries about the shapes of galaxies?

D. To describe some differences between galaxies and clusters

Q2:2.What did Shapley and Ames discover about the universe?

A. Most galaxies are symmetrical.

B. More galaxies exist in the universe than was once believed.

C. Galaxies occur in clusters throughout the universe.

D. Clusters are distributed uniformly throughout the universe.

Q3:3.Why does the professor emphasize the number of clusters mapped by Abell?

A. To help explain why Abell's classification scheme was widely adopted

B. To explain why Abell was the first astronomer to notice spiral-shaped galaxies

C. To provide evidence that Abell's method of surveying galaxies was superior to that used for previous surveys

D. To show how much Abell relied on earlier research

Q4:4.What aspects of clusters did Abell use to classify them? [Click on 2 answers. ]

A. The density of the cluster

B. The shape of the cluster

C. The age of the cluster

D. The type of galaxies in the cluster

Q5:5.Why does the professor discuss the Coma and Virgo clusters?

A. To indicate a limitation of Abell's survey

B. To distinguish between rich and non-rich clusters

C. To demonstrate that clusters considered irregular in shape are basically spherical

D. To illustrate that the shape of a cluster is independent of the shape of the galaxies within it

Q6:6.What is the professor's opinion of Abell's assumption that all clusters are about the same size?

A. He is surprised that it has been disproved.

B. He believes that there is not enough data to support it.

C. He is impressed that it has been proved correct.

D. He thinks it is Abell's most important contribution to astronomy.

四、Distribution Of Galaxies 托福聽力答案：

A1:正確答案：B

A2:正確答案：C

A3:正確答案：A

A4:正確答案：AB

A5:正確答案：D

A6:正確答案：C

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