『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 62 Lec2听力练习：Why are astronomers uncertain as to which of two unnamed galaxies collided with the Cartwheel Galaxy?原文题目答案解析，TPO/Official 62 Lec2听力原文范文音频翻译。

托福TPO/Official 62 Lec2听力原文Why are astronomers uncertain as to which of two unnamed galaxies collided with the Cartwheel Galaxy?【新东方在线】

旁白：请听一段天文学课堂上的讲座部分内容。

Listen to part of a lecture in an astronomy class.

教授：我们几乎了解最大恒星是如何死亡的。

So, we pretty much know how the biggest stars die.

当一颗巨大的恒星走到其存在的尽头时，它会爆炸，释放出巨大的能量，然后在几周或几个月内逐渐消失。

When a massive star reaches the end of its existence, it explodes, sending out a huge blast of energy, which then fades to invisibility within a few weeks or months.

当巨星这样爆炸时，被称为超新星。

When a giant star explodes like this, it's called a supernova.

裸眼看来，超新星似乎是一颗明亮的新星，但它并不是一颗新星——而是一颗正在消亡的恒星。

To the naked eye, a supernova appears to be a bright new star, but it's not a new star—it's a dying star.

然而，超新星产生的冲击波会激发附近的氢气云，使它们压缩并形成新的恒星。这个过程会发出一种独特的辐射。

However, the shock waves from a supernova excite nearby clouds of hydrogen gas, causing them to compress,which does form new stars. And that process emits a distinctive type of radiation.

特别引起我们今天兴趣的是，在星系碰撞的地方也观察到了相同类型的辐射。在这些区域，我们也观察到新星形成的高比率。

Now, a particular interest to us today is that the same type of radiation has been observed in places where galaxies have collided. And In those same areas, we've also observed a high rate of new star formation.

因此并不令人惊讶，我们有一个理论认为是碰撞的星系导致了新星的形成，但没有直接证据。

So not surprisingly, we've had a theory that colliding galaxies caused the new star formation, but there was no direct evidence.

直到最近，一些欧洲天文学家发现了只能由一对碰撞星系产生的冲击波引发的兴奋氢气云。

That is until recently, when some European astronomers found clouds of excited hydrogen gas that could only have been caused by shock waves from a pair of colliding galaxies.

我们过去认为星系是孤立的系统，就像大海中的岛屿。现在我们知道它们总是在移动，通常成群结队。

You know, we used to think of galaxies as isolated systems, like islands in the sea of space. Now we know that they're always moving, usually in clusters.

想想所有涉及的引力作用吧。我们谈论的是由恒星、气体和尘埃组成的巨大系统。

I mean, think about all the gravitational forces involved. We're talking about huge systems of stars, gas, and dust.

由于星系之间的平均距离仅约为其直径的20倍，因此它们经常相遇——我们称之为“遭遇”——这并不令人惊讶。

And since the average separation between galaxies is only about 20 times their diameter, it isn't surprising that they often meet—we call it an encounter.

而且它们以多种方式相遇。例如，合并是最极端的星系遭遇类型。

And they meet in a variety of ways. Mergers, for example, they are the most extreme kinds of galaxy encounters. 

合并是指两个星系相遇，却没有足够的动量继续各自前行，于是合并为一个星系。

A merger is when two galaxies meet and don't have enough momentum to keep going on their separate ways, so they merge becoming one galaxy.

通常情况下，较大的星系会吸收或“吞噬”较小的星系。

Usually, a larger galaxy will absorbs, or sort of swallow, a smaller one.

这种现象可以触发巨大的恒星形成区域，因为来自两个星系的巨大气体云碰撞并坍缩成非常活跃的恒星形成区。

This can trigger huge areas of star formation as enormous clouds of gas from the two galaxies collide and collapse into very active star-forming regions.

碰撞比合并更温和——它们产生较少或相对不那么活跃的恒星形成区。

Collisions are less violent than mergers—that is, they create fewer or relatively less active areas of star formation. 

The galaxies pass through each other, each going its separate way after they collide.

每次碰撞都会向空间中散发一股能量涟漪，推动前方的气体和尘埃。

The collision sends out a ripple of energy into space, plowing gas and dust in front of it.

你的教科书里有一张由哈勃太空望远镜拍摄的星系碰撞照片，非常棒。

Your textbook has a great picture of a galaxy collision taken by the Hubble Space Telescope.

看左图的车轮星系，看起来就像池塘中扔进石头后的涟漪。

See the Cartwheel Galaxy on the left. It looks like the ripples in a pond after a stone has been tossed in.

那是因为右方的一个小星系穿过了它，那明亮的环正是碰撞和压缩气体形成新恒星的地方。

That's because one of the small galaxies on the right passed through it, and that bright ring around, that's where colliding and compressing gases are forming stars. 

但是哪个星系与它相撞了呢？上方右侧的星系已被剥夺了气体和尘埃，这是发生过碰撞的一个明显标志。

But which galaxy collided with it? The one on the upper right has been stripped of gas and dust, which is one clear sign that there's been a collision.

但下方的那个星系显示出大量的新恒星形成，这也是碰撞的证据。所以我们并不确定。

But the one on the bottom is showing a lot of new star formation, which is also evidence of a collision. So we're just not sure.

最后，我们有相互作用。在这种遭遇中，星系交换气体和尘埃但不会真正碰撞。

Finally, we have interactions. In this type of encounter, the galaxies exchange gas and dust but don't actually collide.

许多天文学家认为从我们的银河系延伸到附近另一个星系的气体和尘埃轨迹是相互作用的结果，当时银河系的引力拉扯了另一星系的部分气体和尘埃。

Many astronomers believe that the trail of gas and dust that stretches from our Milky Way Galaxy to one nearby is the result of an interaction, when the gravitational forces of the Milky Way pull some dust and gas off of the other galaxy.

那么恒星呢？它们会不会碰撞？

Student: What about stars? Do they ever collide?

实际上，几乎不会。恒星相对于星系的大小来说很小，而且它们之间相当遥远。

Professor: Actually, almost never. Stars are very small compared to the size of a galaxy, and they're pretty far apart from each other.

小恒星——这个词是相对的，不是吗？很难想象我们在这里谈论的庞大距离。

Small stars—well, that term is relative, isn't it? It's hard to imagine the massive distances we're talking about here.

甚至“遭遇”这个词似乎都有点奇怪，因为这些事件需要很长时间。我们谈论的是数十亿年，这就是为什么我们大多数理论都来自于计算机模拟的原因。

Even "encounter" seems like an odd term, as these events take a long time. We're talking billions of years, which is why most of what we theorize about comes from computer simulations.

否则，我们看到的只是一个阶段的冻结帧——一系列长时间事件中的单张图片。

Otherwise, all we'd see is a sort of freeze frame of whatever stage the encounter is in—a single picture out of a long sequence of events.

但我提到了一些新证据。它来自一对被称为触须的星系。

But I mentioned some new evidence. That's come from a pair of galaxies called the Antennae. 

触须星系处于遭遇的早期阶段，但可能会合并。

The Antennae are at an early stage of encounter but will probably be a merger.

在两个星系重叠的区域发现了兴奋的氢气云。

And excited hydrogen gas has been found in the regions where the two galaxies overlap.

我们知道这一点是因为存在那种独特的辐射特征，并且我们知道超新星的数量不足以解释这种辐射。

We know because that distinctive radiation signature is present, and we know that there aren't enough supernovae to explain the radiation. 

唯一的其他可能性是我们看到了由这两个星系碰撞产生的冲击波结果。

The only other possibility is that we're seeing the result of shock waves produced by the collision of these two galaxies.

What do colliding galaxies and a supernova have in common？(Click on 2 answers）

How does the professor organize types of encounters between galaxies?

Why are astronomers uncertain as to which of two unnamed galaxies collided with the Cartwheel Galaxy?

Why do astronomers believe that the Milky Way galaxy is interacting with another nearby galaxy

What is the professor's opinion of recent observations of the Antennae galaxies?

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