原文已被隐藏，你可用 快捷键 - 或点击 显示原文 按钮来查看原文
1 .<-NARRATOR:->Listen to part of a lecture in an astronomy class.
1 .<-MALE PROFESSOR:->OK, we've been discussing the planets in our solar system, and how some of the ones farthest from the Sun were discovered.
2 .Well, today I'd like to turn to what are called exoplanets, and how researchers detect them. Maria?
1 .<-FEMALE STUDENT:->Exoplanets are planets that orbit around a star other than our Sun, right? They're not in our solar system...
1 .<-MALE PROFESSOR:->Right. They have different, what're called host stars.
2 .[excitedly] The study of exoplanets has been getting more and more exciting; hundreds of them have been discovered so far.
3 .This is quite remarkable in view of the fact that the discovery of the first exoplanets was confirmed only in the mid-1990s.
4 .Now we're finding new ones every few weeks or so.
1 .<-FEMALE STUDENT:->[hesitantly] So, uh-exactly why are we interested in these exoplanets, anyway? Is it to see if there's life on them? '
2 .Because it seems to me like the only exoplanets we ever hear about are gas giants, like Jupiter and Saturn, that couldn't possibly support carbon-based life....
1 .<-MALE PROFESSOR:->OK, well, let's talk about that.
2 .First, as for discovering life... wellll, I think that sort of discovery is pretty far in the future, but it is an eventual goal.
3 .For now, the focus is on locating planets within a host star's so-called [slowly] habitable zone, a zone that's a certain distance from its star.
4 .Because only planets within this zone could conceivably support carbon-based life.
5 .[leading] So what would such a planet need?
1 .<-FEMALE STUDENT:->Water?
1 .<-FEMALE STUDENT:->Yes, it'd need to be the right temperature to sustain liquid water.
1 .<-MALE STUDENT:->And it would need to be a rocky planet....I mean, as opposed to a gas giant....
1 .<-MALE PROFESSOR:->OK, good. An Earth-like planet.
2 .Now, as to that, there are some recently detected exoplanets that might actually be Earth-like.
3 .For example, there's a red dwarf star-that's what most stars are-uh, that's called Gliese 581.
1 .Gliese 581 is... well, it's a lot more interesting than that name makes it seem.
2 .This host star is considered a near neighbor of our solar system because it's only about twenty light-years away.
3 .That's pretty close, by astronomical standards.
4 .And being a red dwarf star, it's small and relatively cool, at least compared with the Sun.
5 .And researchers have discovered planets orbiting Gliese 581.
6 .These exoplanets have been named-ready?-Gliese 581 b, c, d, e... in alphabetical order of their discovery.
这些外星星球被命名为......准备好了吗？它们被按照发现顺序以字母顺序命名，分别是Gliese 581 B, C, D, E。
1 .Gliese 581d and e are the planets I want to focus on now.
Gliese 581 D和E是我现在想集中讲的行星。
2 .See, in 2009 a group of researchers made an announcement: these two exoplanets, Gliese 581d and e, do have some Earth-like qualities.
在2009年，一群研究人员发布通告称：这两个外星星球，Gliese 581 D和E确实有一些类地特质。
3 .Gliese 581d had actually been discovered a couple of years earlier, and when its orbit was originally calculated, it was thought to be too far away from its host star to be warm enough to support a liquid ocean, let alone carbon-based life.
Gliese 581 D实际上是早几年发现的，当最初计算它的轨道时，他们认为它离它的寄主星太远了，没有足够的温度支持一个液态的海洋，更不用说碳基生命了。
4 .But then its orbit was recalculated, and now we see that Gliese 581d is within its host's habitable zone.
但是稍后他们重新计算了它的轨道，而我们现在可以看到Gliese 581 D位于它的寄主星的适居带之内。
1 .<-MALE STUDENT:->So it might have an ocean?
1 .<-MALE PROFESSOR:->Well, conceivably.
2 .See, Gliese 581d weighs seven times what Earth weighs, and it's unlikely that it's made entirely of rocks... because it's so massive.
你看，Gliese 581 D比地球重7倍，不太可能完全都是由岩石组成的，因为它体积太大了。
3 .The researchers studying it said that it could have a rocky core; an ice layer; a large, deep ocean; and an atmosphere.
1 .OK, and there was another announcement, along with the recalculated orbit of Gliese 581d.
除了重新测算Gliese 581 D的轨道还有一个公告。
2 .That was the discovery of another planet in the system, Gliese 581e.
那就是在那个星系又发现了另一个行星，Gliese 581 E。
3 .Compared with other exoplanets, its mass is quite small-only about twice that of Earth's.
1 .<-FEMALE STUDENT:->So is Gliese 581e a more Earth-like planet?
学生：那Gliese 581 E是个和地球更类似的行星吗？
1 .<-MALE PROFESSOR:->Well, we have to consider its orbit.
2 .Gliese 581e orbits its host star in a much shorter period of time than the other planets in the system, meaning it's very close to the star.
Gliese 581 E 环绕它的寄主星运行的时期比该星系其他行星的要短，也就是说它离恒星非常近。
3 .And therefore too hot for water, for an ocean.
1 .However, the fact that it's relatively close to the size of Earth-small, in astronomical terms-that was pretty exciting.
2 .It's impressive that we have the technology to detect it. And it bodes well for future research.
3 .Who knows what we'll find the more we search?