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If you're a fan of astronomy, you probably think you know the story of the first time we discovered a planet outside our solar system.
如果你是天文爱好者，那么你可能认为自己对人类发现系外行星的过程一清二楚。
It goes something like this: Once upon a time, long ago, it was 1995.
你的大概思路是这样的：很久很久以前，1995年的时候。
And by observing changes in a star's motion, Swiss astronomers found our very first exoplanet orbiting the star 51 Pegasi.
通过观察某个星体的运动变化情况，瑞士的天文学家发现了第一颗外星行星，即飞马座51。
It's an amazing story, but it has just one problem:
这个故事不错，但有一个问题：
The planet that came to be known as 51 Pegasi b wasn't the first planet discovered around another star.
飞马座51b非我们在另一颗恒星附近发现的第一颗行星。
Or the second. Or even the third. It just happened to be the first planet we found around a star like our Sun.
还可能有两个甚至三个行星，只不过，这颗行星恰好是我们在类似太阳的恒星附近发现的第一颗行星。
People often forget about the first true exoplanets because they orbit something very different: a pulsar.
大家总是会忘记最早出现的真正的外星行星，因为它们围绕的物体与众不同：脉冲星。
That's right: Between 1992 and ‘94, astronomers discovered a whole star system around one of the weirdest objects in the universe.
没错：1992-1994年间，天文学家发现了一整个恒星体系出现在宇宙最奇怪物体之一的附近。
The pulsar in question is PSR B1257+12, which, thankfully, some astronomers nicknamed Lich. It's about 2300 light-years from Earth.
它就是脉冲星PSR B1257+12。幸运的是，一些天文学家给它起名为Lich，它距离地球大约2300光年的距离。
Like all pulsars, Lich is a special version of a neutron star, an object with a kind of misleading name.
跟所有脉冲星一样，Lich是中子星的特殊版本。中子星的名字有些许误导性。
They aren't stars in the normal sense because they don't convert hydrogen into helium in their cores.
中子星并非一般意义上的恒星，因为它们的核心部分无法将氢转化为氦。
Instead, these objects are actually the leftover cores of other stars.
不仅如此，这些物体实际上是其他恒星留下来的内核。
They form when stars more massive than our Sun end their lives in powerful supernova explosions,
它们之所以能形成是因为比太阳大的恒星在强大的超新星爆炸过程中终结了生命，
which are some of the most violent events in the universe.
而超新星爆炸堪称宇宙里影响力最大的现象了。
As the star explodes outward, its core is compressed under unimaginable pressure.
恒星在向外爆破的过程中，其内核会受到巨大的压力。
So much pressure, in fact, that the electrons and protons inside its atoms are literally crushed together into neutrons.
压力非常之大，以至于原子内的电子和质子在压力下汇聚在一起，形成了中子。
What's left is basically a ball of solid neutrons about 20 kilometers across.
剩下的基本上就是一个固态中子球，直径近20km。
And because that ball is a lot smaller than what the core started as, it also spins a lot faster,
而由于这个球要比一开始小很多，所以转速更快了，
just like how a dancer does when they pull in their arms. Lich, for example, makes an entire rotation every 6.22 milliseconds!
就像舞者挥动双臂转动时的样子，比如，脉冲星每6.22毫秒就能自转一圈。
Most neutron stars have powerful magnetic fields, which can blast out beams of radiation, like radio waves.
大多数中子星都有极强的磁场，可以迸发出大量辐射束，比如无线电波。
Depending on the star's orientation, that beam can sweep across Earth like a lighthouse as the star rotates, sending a pulse of radio waves our way.
根据恒星的朝向，放射束可以在转动过程中像灯塔一样扫过地球，向地球的方向放射出无线电波。
If it does, we call it a pulsar!
如果符合上述描述，就可以称之为脉冲星。
Timing this beam is how astronomers figure out a pulsar's rotation rate, and they're some of the most accurate clocks in existence.
天文学家通过测定无线电波的时间来得知脉冲星的转速，这是现有的最准确的计算方法。
I'm not kidding: Lich's period isn't exactly the 6.22 milliseconds I mentioned earlier. It's actually well, this.
讲真，Lich的周期并非我刚才说的6.22毫秒一圈，事情是这样的。
And that incredible precision is how the very first exoplanets were found.
正是有了这样的精确度，才发现了了第一批外星行星。
In 1992, astronomers studying this recently-discovered pulsar noticed something unusual:
1992年，研究最近发现的脉冲星的天文学家发现了不同寻常的现象：
The timing of this supposedly super-accurate clock seemed to be drifting.
当时，通过这个看似十分精确的计时方法的出来的结果不是很稳定。
It was a tiny change, but it was enough to alter the exact distance between Lich and Earth,
某个细小的改变就足以改变Lich和地球之间距离的计算结果，
meaning its pulses sometimes arrived a little early or a little late.
也就是说，无线电波抵达地球的时间可能会或早或晚。
And since we can normally rely on a pulsar's timing to be very steady,
鉴于正常情况下这种计时方法得到的结果是比较稳定的，
these changes must've corresponded to stuff around it, tugging on the star and affecting its orbit.
所以一定是因为脉冲星周围一定是有什么东西拽着它，影响了它的运行轨迹。
By looking for a pattern in the timing variations, astronomers were able to figure out not only that there were planets, three of them!
通过寻找计时时间的变化规律，天文学家发现，不止一颗，而是有三颗。
but also how massive they were. They started out with some pretty technical names, but they've since been nicknamed Poltergeist, Phobetor, and Draugr.
此外还发现它们质量非常大，一开始，天文学家使用的是技术学名，后来就改成了昵称Poltergeist，Phobetor和Draugr。
And their masses were one of the real surprises: Not only do two of the planets have masses only a few times as much as Earth,
它们的体型之大，让人震惊：其中两个行星的质量是地球的几倍，
but one has a mass similar to our Moon! This makes them some of the smallest exoplanets ever detected.
还有一个跟地球差不多质量，所以，它们是我们观测到的最小的外星行星。
But you probably wouldn't want to visit there.
但大家可能不会有想去这些行星的欲望。
All three orbit their pulsar at least twice as close as the Earth orbits the Sun
这三颗行星围绕中子星的距离至少是地球围绕太阳距离的2倍近，
which is probably a bad place to be with all those powerful magnetic fields.
这样的环境不太适合人类居住，因为这里磁场太强。
Actually, if you think about it, it seems like these planets really shouldn't exist at all.
仔细想一下，不可能存在这样的行星。
They shouldn't have been able to survive the supernova that destroyed their original star. So how'd they do it?
他们不可能在超新星爆炸后才存在，毕竟他们的主恒星已经不在了，那么，它们是怎么做到的呢？
Easy: They probably didn't. It's much more likely that they formed after their host star blew up.
慢着！很可能根本不是我们想的那样，更有可能的情况是，他们的主恒星消失之后，它们才得以形成。
From another star. That was also destroyed.
它们可能是由另一颗恒星形成的，虽然这颗恒星后来也消失了。
Seriously, if you see a star about to blow up, just back away, very, very quickly. It gets nasty in there.
当我们看到某颗恒星即将爆炸时，应该迅速撤离，因为那里会很危险。
Many neutron stars also have companion stars in orbit around them, and Lich may have been no exception.
很多中子星的附近轨道上都有伴星，Lich可能也不例外。
Sometimes, in systems like this, material from that companion star gets pulled onto the neutron star.
在这样的体系中，有时候，来自伴星的物质会受到引力的作用来到中子星上。
It might even be an especially common process for pulsars.
在脉冲星身上，这种现象就更为常见了。
Eventually, if enough material gets stolen, the companion star basically disintegrates, forming a disk of debris around the pulsar.
最后，一旦有了足够的物质，伴星就会解体，并在脉冲星附近形成碎片组成的圆盘。
Now, around regular, young stars, planets form from disks like this.
在规则的新生恒星附近，很多行星都是由碎片圆盘组成的。
So it's reasonable to say that would happen around dying stars, too.
所以，消失的恒星附近会出现新的恒星也不是没有可能。
As far as we can tell, that's likely how Poltergeist and its friends ended up in the universe.
就我们目前所知，非常有可能的是：Poltergeist和它的伙伴行星最后消失在了宇宙中。
Of course, if that all sound like a pretty unlikely scenario to you, the data would agree!
当然了，如果这些在大家听来都是不太可能的话，那我们就拿数据说话吧！
While planets seem to be incredibly common around normal stars, we've found them orbiting less than 1% of known pulsars.
虽然行星似乎在正常的恒星附近非常常见，但我们也发现行星会围绕少于1%的脉冲星运行。
And that's probably a good thing, because pulsar planets have to be among the universe's most tortured objects.
这个比例或许是件好事，毕竟脉冲星的行星是宇宙里备受折磨的行星了：
I mean, how many planets are born from a dying star, while in orbit about another dying star?
有多少行星像脉冲星的行星这样，从即将消亡的恒星中产生，围绕着另一颗即将消亡的恒星呢？
It's not exactly a field of daisies. The first exoplanets we ever found might often get overlooked,
我们不会总是一猜就中，我们发现的第一批系外行星可能总是会受到忽视，
but studying them can remind us that the universe is rarely what we think it's supposed to be like.
但研究它们可以提醒我们，我们对于宇宙的很多想当然都是不符合实情的。
From the very beginning, we knew exoplanets were going to be weird.
从一开始，我们就知道，系外行星是不走寻常路的。
And since the 1990s, we've been proven right over and over again. Thanks for watching this episode of SciShow Space!
自从上世纪90年代以来，系外行星就一再地展现出自己的宇宙不同之处，感谢收看本期的《太空科学秀》！
If you'd like to learn about some of the weird, ridiculous exoplanets we've found since 1992,
如果大家想了解自1992年以来我们发现的风格不寻常的西外行星的话，
you can watch our episode about three exoplanets with some seriously extreme weather.
我们有关于这3颗气候极端的系外行星的集锦哦！
