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为什么冥王星不是行星?

Why Is Pluto Not A Planet?

伙计们,它完了,没救了。我知道,我知道,当我第一次听到新闻时
Guys, it’s done. It’s over. I know, I know, I was as upset as you were when I first
我和你们一样沮丧。我们都学过这样的歌谣来帮助记忆行星,
heard the news. We were taught these songs and sayings to help us remember the planets,
现在它们被毁了。但是冥王星从2006年就已经不是颗行星了,所以,
and now they’re all ruined. But Pluto hasn’t been a planet since, like, 2006, so it’s
该向前看了。但如果你从已被摧毁的音乐和Meg Ryan的电影中看看的话
time to move on. But if you’ve gone through all your breakup music and Meg Ryan movies
你还是不能避开冥王星,所以我们今天在 SciShow Space这里会
and you still can’t get over Pluto, then we here at SciShow Space will get out the
拿出冰淇淋,和你一起蜷缩在长椅上,聊聊这事是怎么发生的。
ice-cream, cuddle up with you on the couch, and talk about how this could’ve happened.
在2006年布拉格的第26次国际天文学联合大会上,冥王星被降级
Pluto was demoted at the 26th general assembly of the International Astronomical Union in
这是个有争议的决定。有天文学家希望保留它
Prague in 2006, and it was a controversial decision. There were astronomers who wanted
但他们唯一能争论的是传统。曾经没有,现在也没有
to keep it, but the only argument they could make was tradition. There was, and is, no
科学依据称呼冥王星为行星。
scientific justification for calling Pluto a planet. It’s a thing out there in the
它是颗在小行星带柯伊伯带内的星星,只有它比海王星远并且它更大些
Kuiper belt which is like the asteroid belt, only it’s out past Neptune and it’s a
柯伊伯带大约有上万亿天体。一百万个百万天体!
lot bigger. There are about a trillion things in the Kuiper belt. A million million things!
并且几乎所有这些天体都是冰块和石块,就像冥王星。
And nearly all of those things are chunks of ice and rock, like Pluto. Pluto is just
冥王星只是我们发现的第一个。
the first one that we saw.
冥王星的确比其中的一些天体大,但不是柯伊伯带中最大的天体
And Pluto is pretty big for one of those things, but it’s not the biggest thing in the Kuiper
那是厄里斯的头衔,其质量大了25%,是冥王星距太阳距离的两倍
belt. That title goes to Eris which is about 25% bigger by mass and twice as far from the
也有其他的大天体,例如妊神星和鸟神星和谷神星
sun as Pluto. There are other big things too, like Haumea and Makemake and Ceres, which
位于火星和木星中间的小行星带中,让其实际上成了一个小个子。科学家
is in the asteroid belt between Mars and Jupiter, making it practically a local. Scientists
预言柯伊伯带将有上百个其他大天体
predict that there may be up to a hundred other big things out there in the Kuiper belt
等待被发现。但是了解了上百颗行星
just waiting to be discovered. But having over a hundred planets would have made those
会让那些歌谣和我们在小学学到的说法变得真的真的很长。
songs and sayings we learned in elementary school really, really long. And that’s really
这才是我们将冥王星降级的关键所在,因为如果我们管冥王星叫行星的话,
the crux of why we had to downgrade Pluto because if we call Pluto a planet we’d have
我们也得同样称呼如此多的其他天体,“行星”这个词就没有用了
to call so many other things planets too that the word ‘planet’ would stop being useful.
所以在2006年,天文学家决定要成为一颗行星,天体必须:环绕太阳飞行,
So in 2006, astronomers decided that to be a planet an object had to: orbit the sun,
有足够的引力使其或多或少地成为球形,
have enough gravity to pull itself into a more or less spherical shape, and have cleared
已经清除自己轨道上的所有东西。最后一条是冥王星不符合的地方
pretty much everything else out of its orbital path. The last one is where Pluto falls short.
冥王星仅比它轨道上的其他物体重0.07倍。地球,
Pluto is only 0.07 times the mass of everything else in its orbit. Earth, just to give you
只是给你一个感受的角度,比轨道上其他物体重1.7百万倍
some sense of perspective, is 1.7 million times the mass of everything else in its orbit.
但是国际天文联合会并非完全无情。
But the International Astronomical Union wasn’t completely heartless. It came up with a new
其创立了天体的一个新分类,只包括前两个标准。
category of celestial objects that satisfies only the first two criteria. We call them
我们叫它矮行星。并且为了让这个特殊的冥王星常驻心中,他们决定
dwarf planets. And in honor of this special place Pluto holds in our hearts, they decided
管所有海王星外的行星叫Plutoids,这……真是太好了。
to call all dwarf planets past Neptune plutoids which is… It’s pretty sweet. And the same
同年,天文学家决定不能再认为冥王星是行星,
year astronomers decided Pluto could no longer be considered a planet, NASA launched the
NASA发布了新视野号以拜访冥王星。新视野号会
New Horizons spacecraft with a mission of visiting Pluto. New Horizons will do a dramatic
在2015年7月激动人心地飞掠冥王星和它的月亮们,并传回许多照片和信息
flyby of Pluto and its moons in July of 2015 and send back lots of photos and information
,其将会史无前例地告诉我们关于我们喜爱的小矮行星。并且它也会
that will tell us more than ever about our favorite little dwarf planet. And it will
捎去我个人最深的祝福
also carry my personal and deepest good wishes.
感谢观看这期SciShow Space,谢谢所有的Subbable订阅者
Thanks for watching this episode of SciShow Space, and thanks to all of our Subbable subscribers
让这个频道成为可能。如果你想要支持我们并且获得一些很赞的装备
who make this channel possible. If you’d like to support us and score some cool gear,
去subbable.com了解更多。如果你对想看的一集节目有问题或想法
go to subbable.com to learn more. And if you have questions or ideas for an episode you’d
你可以在脸书和推特找到我们并在下面评论
like to see, you can find us on Facebook and Twitter and in the comments below, and if
而如果你想和我们一起变得更聪明,只需去youtube.com/scishowspace并订阅
you want to keep getting smarter with us, just go to youtube.com/scishowspace and subscribe.

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