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Right now, we know of eight planets in our solar system, but for more than a century, scientists have been searching for number nine.
目前为止，我们知道太阳系里的行星有8个，但一个多世纪以来，很多科学家都在寻找第9颗行星。
It's a proposed super-Earth: a planet past Neptune much larger than our own.
很多人将第9颗行星成为超级地球：一颗在海王星之外、比地球还大的行星。
Over the years, there's been some evidence that it might exist, and this week, researchers published even more.
过去这些年来，有一些证据表明这颗行星可能存在，而就在本周，研究人员发表了更多的证据。
On Tuesday, scientists announced the discovery of a new, extremely distant object beyond Neptune.
周二，科学家宣布他们在海王星之外发现了一个很远的新物体。
It's detailed in a paper submitted to the Astronomical Journal, and it's named 2015 TG387.
具体内容在论文里可以查看，这篇论文刊登在了《天文学期刊》上。他们将这个物体命名为2015 TG387。
And while it's not a planet itself, it could point us to the long theorized Planet 9.
虽然这个物体并非行星，但它可以为我们研究一直活在理论里的第9颗行星。
The object is pretty tiny, with a diameter of only about 300 kilometers, almost 90% smaller than Pluto's.
这个物体奇小无比，直径只有近300公里，大小只有冥王星的10%左右。
And it's pretty far out. No, like, literally way, way out in the solar system.
而且它距离地球非常远，准确说，就像是出了太阳系一样。
When it was first observed in 2015, as part of an ongoing survey, it was about 80 astronomical units, or AU, from the Sun.
2015年首次观测这个物体的时候（虽然现在观测它已经成了研究的常态内容），当时它距离太阳大概有80个天文单位。
That's 80 times farther from our star than the Earth, or more than twice as far as Pluto is right now.
这是地球距离太阳距离的80倍远，是冥王星距离太阳距离的2倍多。
But comparatively speaking, that's actually really close to us.
但比较而言，跟我们的距离已经很近了。
For 99% of its 40,000-year orbit, this object is so far away we can't even see it.
这个物体环绕飞行已有4万年的历史，而在这岁月99%的时间里，它离的都太过遥远，以至于我们都看不见。
After years of observation, researchers have calculated that, at its farthest, it's a whopping 2300 AU from the Sun, much farther than any other known object.
经过多年的观测后，研究人员根据计算得出，这个物体的最远点距离太阳的距离是2300个天文单位，是我们目前已知的物体中距离太阳最远的。
So far, we've only found two other objects with orbits comparable to this: the dwarf planet Sedna, and the planetoid called 2012 VP113.
目前为止，我们只发现另外两个物体的轨道可以与这个物体相匹敌：一个是矮行星塞德娜，一个是名为2012 VP113的小行星。
These objects are so far out that their orbits are mostly unaffected by the gravity of the eight known planets.
这3个物体太过遥远，以至于它们的轨道几乎不会受到那8颗已知行星引力的影响。
So by studying them, we can learn about the outer solar system and map what's going on out there.
所以，通过研究它们，我们就能了解到外太阳系，并了解到那里的大致情况。
And these orbits may already be pointing to something big.
而且，它们的轨道本身已经为我们提供了重要证据。
All three of these objects, including TG387, share similar orbital paths, almost like they're being shepherded by something larger.
这3个物体，包括TG387在内，都有相似的轨道，就像有什么更大的东西在指引一样。
According to the researchers, that object could be the elusive Planet 9.
研究人员认为，那个物体可能就是神秘莫测的第9颗行星。
To learn more, the researchers ran simulations to see how the gravity of a hypothetical Planet 9 would affect the orbits of these objects.
为了了解更多信息，研究人员进行了多次模拟，想看看活在假设里的第9颗行星的引力是如何影响这些物体的轨道的。
And the results were promising.
结果让人抱有希望。
For one, they showed that these objects did maintain stable orbits.
一方面，结果表明，这些物体确实有着相当稳定的轨道。
In other words, their current paths wouldn't be messed up if a Planet 9 existed out there.
换言之，他们现在的轨道不会因为第9颗行星的存在而被扰乱。
The results also confirmed that a hypothetical planet could be shepherding the small objects.
结果还证实了一件事，那就是这颗虚拟的行星可能指引着一些小型物体。
That could explain why Sedna and TG387 take similar paths.
这也能解释塞德娜和TG387有类似轨道的原因。
But to be sure we need more data, or a direct observation of the planet itself.
为了确认这件事，我们需要更多的数据，或者更直接地观察这颗行星。
Scientists are looking, but since estimates suggest Planet 9 would never get closer to the Sun than 200 AU, it's going to be pretty faint and tough to see, if it exists at all.
科学家还在观察中，但既然有估测表明第9颗行星离太阳最近也不会小于200天文单位，所以还是很难观测到的，不管它是否真实存在。
Now, even if another planet does exist, don't expect us to send astronauts there any time soon.
如今，即便这颗行星确实存在，我们短期内也不会派宇航员去往那里。
Even if we could send a crewed mission that far, research published on Monday suggests we might have trouble surviving the journey.
即便我们能将宇航员送到那样远的地方，周一发表的研究结果也表明：送过去了，也活不下去。
According to the study, which was published in the Proceedings of the National Academy of Sciences, long-term space travel has the potential to seriously damage our GI tracts.
该研究发表在了《美国国家科学院院刊》上，它指出，长期的空间旅行是有可能严重破坏人类GI道的。
The GI, or gastrointestinal tract, is the organ system we use to digest food.
所谓GI就是胃肠道，胃肠道是用来消化的器官系统。
And this new paper suggests that space travel could make it less effective at absorbing nutrients and could potentially cause tumors.
而这篇新发表的论文表明，宇宙飞行会降低我们吸收营养物质的效率，而且很有可能引发肿瘤。
It's all thanks to our good friend cosmic radiation.
这都要归功于我们的好朋友宇宙辐射。
Cosmic radiation mostly comes from objects beyond the solar system, and there are a few types of it, including the extra dangerous heavy-ion radiation.
宇宙辐射几乎都是来自于太阳系外的物体，其种类很少，包括额外的危险重离子辐射。
It comes from supernova explosions, and is made of certain atomic nuclei accelerated to near light-speed.
宇宙辐射来自于超新星爆发，是由特定原子核组成的，这些原子核经过加速后，速度接近于光速。
Because of its mass, it's much more damaging than gamma and X-rays.
由于其质量庞大，其破坏力要比伽马射线和X射线更大。
Thankfully, our planet's magnetic field blocks most of it, but out in the vastness of space, there's not really anything to shield us against its effects.
谢天谢地，我们恒星的磁场可以阻挡大多数宇宙辐射，但一旦置身于广阔的宇宙之中，就几乎没什么防御可以抵挡宇宙射线的影响了。
Previous studies in mice have shown that exposure to heavy-ion radiation can lead to damaged brain tissue and accelerated aging during prolonged space trips.
此前对小鼠的研究表明，暴置于重离子辐射中会导致脑组织损伤，并在长期的宇宙飞行中加速衰老。
And this new paper only adds to the list of potential concerns.
这篇论文只不过是在潜在的风险中加了一条而已。
In the study, researchers exposed mice to low doses of iron radiation, a form of heavy-ion radiation, to simulate the exposure astronauts would receive during a round trip to Mars.
在该研究中，研究人员将小鼠暴置于低剂量的离子辐射中，这样做是为了模拟宇航员在飞往火星期间受到的离子辐射。
Then, these animals were compared to other groups of mice, one which had been exposed to similar amounts of gamma rays, and a control group that received no radiation at all.
随后，将这些小鼠与其他组的小鼠做比较。后两组分别暴置于浓度类似的伽马射线中，以及没有受到任何辐射的实验对照组。
The goal was to isolate the effects of different types of cosmic rays.
目标是隔离开不同类型宇宙辐射的作用。
And what the team found wasn't that encouraging.
但该小组的实验结果却让人提不起信心。
The mice exposed to iron radiation developed cancerous polyps in the soft tissues of their GI tracts, and had fewer enzymes needed for nutrient absorption.
暴置于离子辐射中的小鼠，其肠胃道中的软组织发生了癌性息肉，用于营养素吸收的含酶量也更少一些。
This may have happened if the radiation damaged the DNA in their intestinal walls, making them incapable of normal cell division.
这有可能是因为辐射损坏了肠壁中的DNA，使得DNA无法正常进行细胞分裂。
Now, it is worth noting that not all mice studies translate perfectly to humans, especially when it comes to radiation.
现在，值得一提的是：并非所有的小鼠研究都完美适用于人类，尤其是在辐射这个问题上更是如此。
But since we don't have a good way to protect our spacecraft against these kind of rays, it's worth studying them any way we can.
但鉴于我们没有好方法能保护宇宙飞船抵御宇宙辐射，所以尽可能研究这些对于人类来说是有价值的。
Right now, good shielding materials are just too heavy to get into space, and scientists are a long way from making an anti-cosmic radiation medicine.
目前情况下，好的防护材料重量太大，无法运送到宇宙空间中，而科学家要制造出防宇宙辐射的药物还有很远的路要走。
As people get more serious about going to Mars, though, researchers are looking into every possibility.
随着人们越来越重视去往火星的事儿，科学家还在观望每种可能性。
These kind of studies are good reminders that space exploration is more than just building big rockets:
这些研究给我们提了个好醒，即太空探索并非只是建造大型火箭而已：
We also need to learn how to take care of the people on board.
此外，我们还需要了解如何体恤太空舱里活生生的人。
But someday, when we're walking around on Mars or maybe even Planet 9, it will all be worth it.
但或许某一天，当我们在火星或者第9颗行星上到处溜达的时候，这一切辛苦都是值得的。
Thanks for watching this episode of SciShow Space News!
感谢收看本期的《太空科学秀》！
If you'd like to help us make more episodes like, you can go to patreon.com/scishow.
如果您想帮助我们制作更多类似于本期的视频的话，不妨登录patreon.com/scishow。
And to all of our current patrons, thank you! Our team couldn't do all of this without you.
这里还要对我们的所有忠实粉丝道一声感谢！我们的团队有了你们才能走到现在。
