评论
打印
With so many galaxies getting ripped apart or smashing into each other, you might think of our Milky Way as a comparatively peaceful place.
我们的宇宙里有很多个星系要么彼此分隔，要么相互纠缠，这可能会给人一种感觉——银河系是个相对和平的地方。
Well, sorry about that.
这个嘛，可不是这样哦。
Because it's actually a cannibal.
因为银河系其实是个自相残杀的地方。
We've seen evidence of the Milky Way devouring other galaxies before, and now, it seems like we've found another one.
我们已经发现有证据表明银河系曾吞食过其他的星系。现在，似乎这样的罪证又多了一条。
In this month's issue of the Monthly Notices of the Royal Astronomical Society,
在本月发表的《皇家天文学会月报》中，
scientists announced evidence suggesting that, 8 to 11 billion years ago, the Milky Way devoured a neighborhood they call the Sausage Galaxy.
科学家宣布发现证据表明：80-110亿年前，银河系曾吞食过一个邻居星系，名作"香肠"星系。
I mean if you're gonna eat a galaxy, it might as well be a sausage galaxy.
不过，如果要吞食星系的话，是不是香肠形状的又有什么关系呢？
According to an international team of astronomers, some stars hanging out in the Milky Way's halo, a sort of spherical cloud full of stuff like old stars, serve as a record of this event.
一组国际天文学家表示，银河系有类似于球状幸运的光晕地带，里面到处都是年代久远的恒星之类的星体，这些恒星可以证明银河系确曾吞食过"香肠"星系。
Or, more specifically, their orbits do.
或者更准确的说，证人是这些恒星的轨道。
These orbits are super long and narrow, oriented radially with respect to the center of the Milky Way.
这些恒星的轨道超级长，而且十分狭窄，他们会围绕银河系中央进行旋转。
These stars also have a noticeably different chemical makeup than other ones nearby, and the directions of their orbits go backwards.
此外，这些恒星的化学组成结构与附近的其他恒星迥然不同，他们轨道的方向也与其他恒星相反。
So the team concluded that they probably had to have come from a different galaxy.
于是，该小组下结论认为，这些恒星极有可能是来自另一个星系的。
Since plots of these stars' velocities relative to others in the area look vaguely sausage-shaped, the team dubbed the stars "Gaia Sausage" and the galaxy they came from the "Sausage" Galaxy.
根据这些恒星与该区域其他恒星相对速度所勾勒出的图谱形状大致与香肠一致，所以该研究组将这些恒星称为"盖亚香肠"，将它们来自的那个星系称为"香肠"星系。
It almost definitely didn't look like a sausage itself, though.
不过，这个星系本身与香肠并无相似之处。
Although that would be awesome, because it would totally team up with that galaxy that looks like a fried egg.
不过，叫"香肠"星系也不错，因为这个星系形状很像煎蛋，煎蛋和香肠还蛮搭的。
Anyway. Just call me when they find a galaxy that looks like poptarts; I'll be there for that.
没准哪天还有个星系叫果酱馅饼，到时候记得告诉我哦。
When this galaxy collided with the Milky Way, it likely caused our disk to puff up, or it might've even broken part of it up and forced it to reform.
香肠星系跟银河系发生撞击时，很有可能导致银河系发生肿胀，或者可能导致银河系的部分地区分崩离析，发生重组。
Essentially, the Sausage's guts got scattered around the inner Milky Way, adding to our galaxy's bulge.
关键部分在于：香肠星系的内部恒星分散在了银河系内部的周边，使银河系变得更加肿胀。
You know, when you have too many sausages.
就像凭空塞了很多香肠的感觉。
Telescopes like the Hubble have collected a lot of beautiful images of galactic collisions, but we don't have a time machine or a camera outside of the Milky Way to see them happen to us.
哈勃望远镜这样的设备已经收集过银河系撞击的许多绝美画面，但我们在银河系之外没有时光机和摄影机，所以也无法站在旁观者的角度观测这样的过程。
So, the team had to use computer models to check if the observed stellar positions and the trajectories could be produced by this hypothetical Milky Way/Sausage Galaxy interaction.
所以，该研究组只能通过计算机模型来查验观测到的星体位置及其轨迹是否能通过银河系/香肠星系的相互作用而产生。
The simulations used data from both the Sloan Digital Sky Survey and the ESA's Gaia satellite, which is mapping stars in our galaxy and how they move through space.
模拟过程中用到了史隆数位巡天以及欧洲航天局盖亚卫星的数据，反映出了银河系恒星的位置及其移动方式。
And they concluded that a galaxy roughly 5% the mass of the Milky Way with an extremely eccentric orbit could produce these leftover stars with weird orbits.
他们的结论是：质量大约是银河系5%的星系，倘若其轨道十分古怪的话，就会产生轨道同样古怪的残留恒星。
Of course, this wasn't the first time the Milky Way ate another galaxy, and it won't be the last.
当然了，这并不是银河系第一次吞食另一个星系，也不会是最后一次。
But the Sausage hypothetically contributed the bulk of the stars in the inner stellar halo, which is a helpful thing to know about.
但是香肠星系在我们的假想里确实是给银河系内部的星体光晕提供了大量的恒星，知道这一点是非常重要的。
In another paper, the team of astronomers also identified at least eight globular clusters, which are dense, spherical clusters of stars, that might have originally belonged to the Sausage galaxy, too.
在另一篇论文中，这组天文学家还发现了至少8个球状星团，他们密度很高，经多颗恒星聚集形成了球状。这些星团一开始可能也是来自于香肠星系的。
But since the paper hasn't completed the peer-review process yet, we can't really say that for sure.
但是，鉴于这篇论文尚未经过同行评审，所以我们无法下定论。
Meanwhile, while the U.S. was blasting off fireworks last week, another team was getting ready to share findings about different light shows on Jupiter.
上周，对于这件事，美国舆论有不同的看法，这个暂且不提了。我们来聊聊有关木星上光影的一些新发现吧。
Specifically, auroras, which happen when electrons get accelerated by Jupiter's magnetic field.
更准确的说，其实就是极光，当木星磁场使电子加速的时候就会产生极光。
The process is similar to how some auroras form on Earth, but on Jupiter, some of the planet's moons actually help shape what these shows look like.
木星的极光与地球极光的形成过程相似，但木星的一些卫星实际上对于极光的形成有一定的促进作用。
A study published last Thursday in the journal Science shed a little more light on the subject and also showed that these interactions are more complicated than we thought.
上周四，《科学》杂志上发表了一则研究，这则研究有助于理解这个话题。
Jupiter has upwards of 60 moons, but the most famous are those discovered by Galileo at the start of the 17th century: Io, Europa, Ganymede, and Callisto.
木星有60个卫星，但其中最出名的要属加里罗17世纪初发现的那几个：木卫一、木卫二、木卫三、木卫四。
All of them orbit within Jupiter's magnetosphere, or the region ruled by its magnetic field.
他们都在木星的磁层以内运行。所谓磁层就是受木星磁场作用的区域。
And they're close enough to the planet that they form sort of an obstacle to any charged particles trying to follow Jupiter's super strong magnetic field lines.
由于这几个卫星跟木星的距离了很近，所以会给那些被木星超强磁场线带动的带电粒子形成一种阻碍的作用力，
Basically, this causes a special kind of magnetic wave to form, called an Alfven wave.
这个过程中就会形成一种磁波，名作阿尔文波。
It accelerates electrons toward Jupiter's atmosphere and causes additional auroral emissions.
阿尔文波会使电子向木星大气层加速移动，产生额外的极光现象。
This leaves a noticeable footprint in Jupiter's atmosphere, showing up as bright spots in both the north and south hemispheres.
这个过程会在木星的大气层上留下显著的印记，表现为木星北半球和南半球出现的亮点。
Astronomers have previously used the Hubble to study these features, but now that we have the Juno spacecraft orbiting Jupiter's poles, we have a much better vantage point.
天文学家之前曾通过哈勃望远镜来研究这些特征，但鉴于我们现在已经有了朱诺航天器环绕木星两极飞行，所以也就有了更好的有利位置。
In this new paper, one team used Juno's Jovian Infrared Auroral Mapper, or JIRAM, to reveal the hidden complexity within these footprints.
在这篇新发表的论文中，一个研究组通过朱诺的木星极光红外成像仪(JIRAM)揭示出了这些印记中隐藏的复杂性。
In September 2017, JIRAM set its sights on where models expected Io's footprint to show up.
2017年9月，木星极光红外成像仪开始关注木卫一的印记会在模型的哪里显现。
Since Io is the closest of the Galilean moons to Jupiter, it leaves the largest footprint.
由于木卫一是伽利略发现的卫星中距离木星最近的一颗，所以其留下的印记也最大。
And one did show up there, but it was a lot more than just a big spot.
确实也发现了一个印记，这个印记比大亮点还要大。
Images revealed a trail of swirling vortices in both hemispheres, which sometimes split into two wing-shaped arcs.
多幅图像显示，木星的两个半球上都出现了旋转的涡流，而且涡流还会分裂为2个翅膀形状的弧形。
The main spot was located where models predicted, but secondary shadows stretched for a thousand kilometers or so on each side, each about one Io diameter away from each other.
主要的印记点就在模型预测的位置上，但其留下的影子分别在两侧延伸了1000公里，彼此之间的距离都有木卫一直径那么长。
While the pattern is clearly something reminiscent of fluid dynamics, like air swirling off a plane wing, the team doesn't have a specific model that explains how Io's path through Jupiter's magnetic field creates it.
虽然这个模型显然跟流体动力学脱不开干系，比如飞机机翼下产生的气旋一样，但该研究组还是没有准确的模型，所以无法解释木卫一是如何通过木星的磁场来使流体动力学发挥作用的。
They suggest the Alfven waves might be broken into smaller waves with different travel paths, which could lead to something so turbulent looking.
这些天文学家认为，阿尔文波可能是被分解成了路径不同的小波，继而导致看似激烈的情况出现。
But they're not positive yet.
但他们还不确定是不是这样。
Still, the fact that something as small as Io can have such a big influence on Jupiter is pretty cool.
不过，像木卫一这样的小行星可以对木星有如此重大的影响，这件事确是意想不到的。
The team also captured images of Ganymede's footprint, revealing never-before-seen double shadows of sorts, with two identical spots roughly 170 kilometers apart.
该研究组还捕捉到了木卫三留下印记的一些图像，图像上显示出了此前从未见过的两倍的印记，此外还有2个相同的亮点，大致有170公里远。
This might be due to the fact that Ganymede is the only moon to have its own magnetic field, but again, more data would help.
这可能是因为木卫三是唯一一个有自己磁场的行星，不过这一点还需要有更多的数据才能证实。
The good news is that Juno has at least another three years of work to do, so we'll have time to make more observations.
好消息是：朱诺还能再工作3年的时间，所以我们还能获得更多的观测数据。
And someday, we'll hopefully have a better idea of how Jupiter's magnetic field reacts to such a complex system.
或许有一天，我们有希望能更加了解木星磁场对这样一个复杂体系的作用机制是怎样的。
We've also observed Enceladus's auroral footprint on Saturn, so we know that this isn't something unique to Jupiter.
此外，我们还观测了土卫二在土星上留下的极光印记，然后我们得知了这种现象并不是木星特有的。
In fact, these auroral footprints could be found where there's any electrically-conducting moon orbiting inside a planet's magnetosphere, or even a planet inside a star's.
实际上，只要一颗行星的磁层内有电磁作用的情况，或者有行星在恒星内的情况，就会留下极光的印记。
So one day, we might look back on these Juno observations as a major step toward understanding a much bigger picture.
所以，某一天，我们或许会发现，朱诺观测到的这些情况让我们更加了解了这件事情的来龙去脉。
Thanks for watching this episode of SciShow Space!
感谢收看本期的太空科学秀！
Besides influencing Jupiter's auroras, it turns out Io has a lot more to brag about, like, the fact that it might have an underground magma ocean.
除了能影响木星的极光产生之外，木卫一还有更多厉害的地方，比如木卫一或许还有地下岩浆海。
You can find out all about that in an episode we did on Io.
我们有一期是专门介绍木卫一这部分内容的。
