『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 71 Lec2听力练习：What is the main purpose of the lecture?原文题目答案解析，TPO/Official 71 Lec2听力原文范文音频翻译。

托福TPO/Official 71 Lec2听力原文What is the main purpose of the lecture?【新东方在线】

旁白： 听一段天文学课程的讲座。

Narrator: Listen to part of a lecture in an Astronomy class.

教授： 在1995年之前，我们所知道的唯一行星是那些围绕我们自己太阳运行的行星。

Professor: Before 1995, the only planet we knew about were those in orbit around our own son.

我们所知道的关于行星的一切都是基于它们，即我们自己太阳系中的行星。

Everything we thought we knew about planets was based on them, the planets here in our own solar system.

最大的问题是，行星是如何形成的？

The big question was, how did the planets form?

当时占主导地位的理论是核心吸积理论。

And the prevailing theory back then, was the core accretion theory.

根据核心吸积理论，当太阳在一个巨大的、扁平的旋转气体和尘埃盘的中心形成时，有一些剩余的物质没有参与形成盘的大小，这些物质在盘中不断旋转，碰撞并粘在一起。

According to the core accretion theory, when the sun formed in the middle of a huge, flat spinning disk of gas and dust, there were some leftovers stuffs that didn't go into making the size the disk kept swirling around bits of matter collided, and some stuck together in clumps.

经过数百万年，一些团块聚集在一起，创造了越来越多的物质，最终长大到足以形成岩石核心。

And over millions of years, some clumps gathered and created more and more material and eventually grew large enough to form rocky cores.

但由于太阳的能量在长时间内的影响，靠近它的行星无法很好地保持轻气体。

But due to the sun's energy over long periods of time, the cause of planets closer to it couldn't hold on to light gas is very well.

所以它们仍然是像地球一样的小型岩石行星。

So they remained small, rocky planets like earth.

与此同时，虽然离太阳较远的行星，它们的引力仍然不断吸引气体分子。

Meanwhile, though the planets farther out from the sun, their gravitational force kept on pulling in gas molecules.

而这些较冷的行星能够缓慢地吸引并保持大量的气体。

And these colder planets could creep and hold on to huge amounts of gas.

最终形成了像木星这样主要由气体组成的巨大行星。

You ended up with giant planets such as Jupiter composed largely of gas.

这种聚集的最终结果就是你在我们的太阳系中看到的。

The final result of this accretion is what you see in our solar system.

靠近太阳的岩石行星和远处的气体巨星。

Rocky planets near the sun and gas giants farther out.

然后还有那个奇特的冥王星，我们暂时就不理它。

And then there's the oddball Pluto which will just ignore for the time being.

1995年，科学家们发现了一颗新行星，它不是围绕我们的太阳，而是围绕另一颗恒星。

In 1995, a new planet was discovered in orbit, not around our son, but around a difference of sun.

这不仅仅是一个伟大的第一次，而且是51 Pegasus b的发现，他们就是以此命名的第一个太阳系外行星。

This was not just a great first in itself, but the Discovery of 51 Pegasus b that's what they named this first extra solar planet.

这立即挑战了行星形成的核心吸积理论。

This immediately challenged the core accretion theory of planet formation.

这是因为51佩古苏斯b是一颗气体巨星，轨道非常接近其恒星。

That's because 51 Pegasus b is a gas giant that orbits very close to its sun.

事实上，它距离其恒星的距离是水星的八倍，而水星是离我们太阳最近的行星，八倍之远且是一个气体巨星，这一理论并没有预测到如此之近。

In fact, eight times closer to its sun, the mercury, which is the closest planet to our sun, 8 times closer and a gas giant, which theory would not have predicted so near.

显然，需要一种不同的行星形成理论。

Clearly, a different theory of planet formation was needed.

因此，盘不稳定性理论应运而生。

盘不稳定理论已经存在了一段时间。

The disk instability theory had been around for a while.

但在发现51白羊座b之前，它并没有引起太多关注。

But hadn't gained much attention until the Discovery of 51 Pegasus b.

这个理论基本上说，如果围绕新生恒星的气体盘足够大且足够冷，那么盘内的任何重力不均匀性都可能导致团块的形成。

The theory basically says that if the gaseous disk around a newborn star is massive enough and cold enough than any unevenness of gravity within the disk could cause clumps.

甚至在短短 1,000 年内就能形成巨大的气体团块，这些团块随后可能会成为气体巨星。

Even giant clumps of gases to form in as little as 1,000 years, those clamps could then become gas giant planets.

所以，盘不稳定理论认为，巨型行星可以在靠近太阳的地方形成，而不需要很长时间。

So the disk instability theory says giant planets could form near a sun without needing a long time to do it.

一个小小的，好的，一个重大的发现如何能改变我们认为的真相。

How one little, ok, one momentous discovery can change what we thought we knew was true.

好像仅仅有这两种竞争的行星形成理论还不够。

Well as if it wasn't enough to have these two competing theories of planet formation.

然后又提出了一个与核心积累理论有些相关的理论。

Another one somewhat related to the core accretion theory was then proposed.

一些天文学家仍然不相信气体巨星行星会如此靠近太阳形成。

Some astronomers remain unconvinced that a gas giant planet could form so close to a sun.

其中，他们怀疑气体会在那儿持续很长时间，因为太阳强烈的辐射可能会将它们吹走。

Among other things, they doubt that gases would last very long there, because the sun's intense radiation could just blow them away.

And they support the idea of orbital migration.

轨道迁移理论表明，气体巨星行星最初形成在离其恒星很远的地方，但随着时间的推移，它会移动到比你预期的小型岩石行星更靠近恒星的位置，并且如此大行星的强大引力即使在靠近恒星时也能保持其巨大的大气层。

The orbital migration theory suggests that a gas giant planet forms far from its sun, but then over time moves to a position even closer to that sun than where you'd expect to see smaller rocky planets, and the powerful gravity of such a large planet holds on to its massive atmosphere, even when it's so close to that sun.

所以，我们发现这颗气体巨星行星轨道非常接近它的太阳。

So, we find this one gas giant planet orbiting very close to its sun.

然后，事实证明，51 佩加索斯 b 根本不是独一无二的。

And then, well, it turns out that 51 Pegasus b is not at all unique.

这只是我们发现的一系列大型气态行星中的第一个，我们喜欢称之为热木星，因为它们的大小与木星相当或更大。

That is just the first of a number of large gaseous planets we found that we like to call hot Jupiter because they're about the size of Jupiter or larger.

而且离它们的太阳非常非常近，所以非常非常热。

And close enough to their suns to be very, very, hot.

所以，如果我们对行星形成的所有信念都是基于我们自己的太阳系，而事实证明我们的太阳系至少缺少一种相当常见的行星类型。

So, if all we believed about planet formation was based on our own solar system, and it turns out that our solar system lacks at least one fairly common type of planet.

那么，这说明了我们对宇宙的真正了解有多么有限呢？

Then what does that say about what we really know?

What does the core accretion theory predict based on the distance of planets from their sun? Click on 2 answers.

What does the disk instability theory imply about planets?

According to the orbital migration theory, what is assumed about a gas giant planet that is orbiting very close to a sun?

What does the professor imply when he says this:

What does the professor mean when he says this:

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