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Over the past 50 years or so, we've gotten pretty good at exploring our solar system.
大概近五十多年来，我们对太阳系的探索收获颇丰。
And one day, maybe our spacecraft will regularly venture beyond that into interstellar space.
甚至或许有一天，我们的宇宙飞船可以定期探索太阳系外的宇宙空间。
Still, there are a lot of challenges we'll need to tackle to achieve that goal, including navigation.
不过，我们依然需要解决很多的挑战才能实现这个目标，其中就包括星际导航的问题。
After all, space is big, and it's not like there's a galactic version of GPS.
毕竟宇宙这么大，可不像一个银河版GPS那么简单呢。
But this month, researchers announced developments on a promising way we could someday steer spacecraft on deep space missions: using pulsars.
不过这个月，一些天文学家宣布他们研发了一种方法，有望让人类通过操控宇宙飞船来进行深空探索任务：通过脉冲星。
Pulsars are the leftover, super-dense cores of massive stars that went supernova.
脉冲星大质量恒星变为超新星后留下的超密内核。
They spin super fast as often as thousands of rotations every second
脉冲星自转速度极快，频率高达每秒上千转。
and their incredibly strong magnetic fields accelerate particles away from them in jets. Those jets emit a lot of radiation.
此外，脉冲星磁场极强。高频以及喷发出的射流都让粒子加速远离脉冲星，因为射流会释放大量辐射。
In a way, they're kind of cosmic lighthouses.
从某种角度看，他们有点宇宙中灯塔的意思。
If a pulsar is oriented correctly with respect to Earth, its rotating jets will sweep across our line of sight and make its signal appear to pulse.
如果脉冲星与地球的角度正好，那么其旋转射流会横扫我们的视线，让其发出的信号看起来像脉冲一样。
Because those pulses are so regularly-timed, we've thought for decades that pulsars could be used like beacons.
由于脉冲的发出是有规律的，所以几十年来我们一直以为可以将脉冲星作为信号塔。
In theory, a spacecraft could determine its position by tracking the signals it receives from multiple pulsars.
理论上讲，宇宙飞船可以通过追踪其从多个脉冲星接收到的信号来判断其所处的位置。
It was such a promising idea that, in the 1970s, a map of how to find our solar system relative to 14 different pulsars
这个想法很有前景，所以，上世纪70年代，先驱者号和旅行者号飞船上准备了一幅地图，
was included on the Pioneer and Voyager spacecraft.
地图展示了如何通过与太阳系相关的14个不同的脉冲星来确定太阳系的位置。
Although, back then, it was only a theoretical tool. Our technology just wasn't ready for the job.
不过，这在那时候只是个理论上的工具而已，那时候人类的技术还不足以完成这项定位工作。
But this month, at an American Astronomical Society meeting, NASA researchers announced that pulsar navigation is one step closer to reality.
不过就在本月，在美国天文学会的一次会议上，一些美国宇航局的研究人员宣布，脉冲星导航离成功又近了一步。
Last November, they tested this method using the SEXTANT enhancement on a washing machine-sized instrument on the International Space Station.
去年11月，他们在国际空间站上一个洗衣机一般大小的仪器上，通过六分仪增强方式检测了这种方法的可操作性。
With it, the team was able to pinpoint the Station's position to within about 5 kilometers using the x-ray emissions from just four pulsars.
有了这种方法，该研究组仅通过四个脉冲星发出的X光线来定位方圆五千米内国际空间站的位置。
That's pretty impressive, considering the ISS is flying around the Earth at around 28 thousand kilometers per hour.
这很难得，毕竟国际空间站环绕地球飞行的速度高达每小时近2800千米。
Pulsars are found all over galaxy, so one of the perks of navigating by them is they can be used anywhere in space.
银河系里的脉冲星多不胜数，所以通过脉冲星来导航的一个优势就是：在哪里都可以用。
But perhaps the most important perk is autonomy.
但或许最重要的优势是自主性强。
Pulsars remove the need for spacecraft to regularly communicate with Earth to steer.
有了脉冲星，星际航行的时候，宇宙飞船就可以定期与地球传送信号来确定方向。
Instead of waiting for commands from Earth, pulsar navigation would allow a spacecraft to make small decisions by itself.
通过脉冲星导航就不必等地球发来的指令，宇宙飞船可以自己做决定。
It would also allow a craft to change trajectory during times when it can't connect with Earth like if the Sun is in the way.
通过这种导航方式，即便宇宙飞船因为太阳挡在中间而无法与地球联系，也能让宇宙飞船改变航向。
So far, this research is just proof of concept, and it could take years to implement a galactic positioning system in real spacecraft.
目前为止，该研究只印证了概念，要在实际的宇宙飞船中对星系进行定位还需要数年之久。
But a second SEXTANT experiment is set for later this year,
不过，今年下半年已经确定要做第二次六分仪实验。
and astronomers are working both on improving the algorithms behind it as well as designing a smaller, more lightweight instrument.
与此同时，天文学家们正在一边精进其背后的算法，一边着力设计一种更小、更轻的仪器。
Because in space, size matters! And something the size of a washing machine just won't do.
毕竟在宇宙里，体型小巧是关键因素啊！像洗衣机那么大的仪器是不可能适用的。
We might still be figuring out how to navigate interstellar space, but there is a place in the solar system with a brand new map:
我们或许还是可以试图寻找星际航行的方法，但太阳系里有一个崭新的地图：
Titan, Saturn's largest moon.
土卫六泰坦，土星最大的卫星。
Last month in Geophysical Review Letters, astronomers published the most advanced topographic map of Titan to date,
上个月，一些天文学家在《地球物理学评论快报》里发表了目前为止土卫六最先进的地形图，
as well as a paper announcing new revelations and new mysteries.
以及一篇论文，论文里提到了一些新的发现，当然也有新的谜团。
Scientists are especially interested in Titan because it's a bit of an oddball.
天文学家对土卫六尤为感兴趣的原因是土卫六有点奇怪。
For one, it has a super thick, nitrogen-rich atmosphere, while most moons don't have much of an atmosphere at all.
一方面，土卫六密度极高，大气中氮含量丰富，而大多数的卫星并不具有这样的环境特点。
It's also the only object besides Earth where we've definitely found liquid on its surface although it's not water.
此外，土卫六还是唯一一个除了地球之外表面有液体的卫星，虽然那液体并不是水，
It's simple organic molecules like methane and ethane, which are made of carbon and hydrogen.
而只是甲烷和乙烷那样的有机分子，由碳和氢组成。
This new map combines all the data from the Cassini mission to Saturn, which ended last year, but computer algorithms had to help fill in the gaps.
这幅新地图上包含了卡西尼号太空船到土星的所有数据。虽然该任务去年就结束了，但计算机算法得填补其中的一些空白。
It probably won't explain Titan's weird atmosphere or anything, but the map is already helping astronomers better understand the moon's surface features.
虽然这幅地图很可能无法解释土卫六的环境等方面为何如此奇怪，但是这幅地图已经帮助天文学家更好地理解了土卫六的地貌。
The map showed new mountains, helped refined measurements of Titan's shape, and revealed that Titan's three hydrocarbon seas all sit at the same elevation.
这幅地图上有新的山脉，助力精确测量了土卫六的形状，并发现土卫六上的三个甲烷海洋海拔都相同。
In other words, they form a single sea level, just like Earth's oceans do.
换言之，它们只有一个海平面，就像地球上的所有海洋一样。
Mostly, this is cool because it means Cassini took really accurate data.
这一点在大多数情况下是有利的，因为卡西尼号采集到的是真正精确的数据。
Like, it could measure altitude with accuracy down to 40 centimeters!
所以，测量其山脉高度可以精确到40厘米。
The map also proved that some of Titan's lakes which are isolated from its seas are connected with each other underneath the surface.
这幅地图还证明，一些土卫六的湖泊虽然与海并不相连，但彼此之间在地下是互相连通的。
They noticed this because, for groups of lakes that share the same drainage basin, all of the dry lake beds sit at higher elevations than nearby filled lakes.
天文学家注意到这一点是因为对于有相同流域的湖泊群来说，所有干涸的河床都比附近水量充裕的湖泊海拔要高。
But there weren't any visible rivers flowing from one lake to another.
但是湖泊与湖泊之间并没有明显的河流贯通。
That means the liquid likely used underground channels to drain into the lakes closer to sea level.
也就是说，甲烷海洋很可能通过地下的水道排入与海平面差不多海拔的湖泊里。
Maybe the weirdest new discovery about the moon were depressions that look a bit like someone took a cookie cutter to Titan's surface.
或许关于土卫六最奇怪的新发现就是它表面坳陷的样子，就好像有人带饼切去过一样。
They're flat-floored lake basins surrounded by ridges hundreds of meters high!
他们由数百米高的脊系环绕，看起来很像平地湖泊盆地。
They appear to have formed the same way certain terrain, called karst, does on Earth:
他们的形成方式与地球上喀斯特地形的形成方式一样：
when underground material is dissolved by running liquid, then the surface material collapses to form a giant hole.
地下的物质被流动的液体溶解后，地表的物质就塌陷，形成了大坑。
But on Titan, the rims of these depressions are sharper, and the walls are steeper.
而在土卫六上，坳陷的边缘更加尖锐，形成的墙壁更加陡峭。
Right now, it's still a big mystery how these features formed and evolved
现在，人类对于这些地形是如何形成发展的一概不知。
and if they mean anything for Titan as a whole but we probably won't have an answer any time soon.
就算这种地形真的能解释土卫六的很多现象，我们在短期内也无法得知。
We'll have to wait until Titan gets another satellite visitor to get more high-resolution data.
我们得等土卫六有其他的卫星后，才能获得更多的高清数据。
But in the meantime, we can at least continue to dig through what Cassini provided over its 13 years zooming around Saturn.
但与此同时，我们至少可以继续探索卡西尼号在环绕土星13年间所获得的数据。
And this new map is only the beginning.
而这幅地图只是个开始。
Thanks for watching this episode of SciShow Space News, and special thanks to our patrons on Patreon who make it all possible.
感谢收看本期的《太空科学秀》，尤其要感谢我们的赞助商Patreon。
If you'd like to help us keep bringing you news from around the universe, you can go to patreon.com/scishow.
我们关于宇宙的其他消息，您可以登陆patreon.com/scishow了解更多。
