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绿岸基地:被遮挡的星光?

The most mysterious star in the universe | Tabetha Boyajian

非同寻常的结论 需要非同寻常的证据
Extraordinary claims require extraordinary evidence,
作为天文学家 这是我的职责和责任
and it is my job, my responsibility, as an astronomer
去提醒人们 外星人假说永远都是最后的解释!
to remind people that alien hypotheses should always be a last resort.
现在我要给你们讲这么一个故事
Now, I want to tell you a story about that.
故事中有来自NASA项目中的数据
It involves data from a NASA mission,
有普通人 还有一颗银河系里最非同寻常的星星
ordinary people and one of the most extraordinary stars in our galaxy.
故事开始于2009年 NASA启动了开普勒计划
It began in 2009 with the launch of NASA’s Kepler mission.
开普勒计划的首要科学目标
Kepler’s main scientific objective
是寻找太阳系以外的行星
was to find planets outside of our solar system.
它持续观测一小块天区
It did this by staring at a single field in the sky,
就这块 所有这些小方块
this one, with all the tiny boxes.
在这小块区域中
And in this one field,
它持续观测超过15万颗恒星的亮度
it monitored the brightness of over 150,000 stars
整整四年
continuously for four years,
每30分钟就采集一次数据
taking a data point every 30 minutes.
它在搜寻天文学家 叫做掩食的东西
It was looking for what astronomers call a transit.
它发生在行星轨道 和我们的观测视线重合情况
This is when the planet’s orbit is aligned in our line of sight,
这样行星就会从恒星前面经过
just so that the planet crosses in front of a star.
这种情况下 行星就会挡住一点点的星光
And when this happens, it blocks out a tiny bit of starlight,
你可以在光度曲线上 看到小小的负峰
which you can see as a dip in this curve.
于是 NASA团队开发出非常复杂的电脑程序
And so the team at NASA had developed very sophisticated computers
来搜寻开普勒数据中的掩食事件
to search for transits in all the Kepler data.
在首次数据发布的同时
At the same time of the first data release,
耶鲁大学的天文学家在考虑一个有趣的问题:
astronomers at Yale were wondering an interesting thing:
万一电脑错过了什么怎么办?
What if computers missed something?
于是我们又发起了一项 名为“行星猎人”的公民科学项目
And so we launched the citizen science project called Planet Hunters
这个项目依靠大众来分析同样的数据
to have people look at the same data.
人脑有着惊人的模式识别能力
The human brain has an amazing ability for pattern recognition,
有时候甚至比电脑都厉害
sometimes even better than a computer.
然而 这个项目遭到了很多质疑
However, there was a lot of skepticism around this.
我的同行黛布拉·费舍尔 行星猎人项目的发起人
My colleague, Debra Fischer, founder of the Planet Hunters project,
说那时候人们议论道:
said that people at the time were saying,
你们疯了 电脑绝不可能错过信号
“You’re crazy. There’s no way that a computer will miss a signal.”
所以这又是人和机器 赌哪个的老段子
And so it was on, the classic human versus machine gamble.
如果我们发现了一颗行星 那我们就会特别高兴
And if we found one planet, we would be thrilled.
四年前在我加入这个团队的时候
When I joined the team four years ago,
我们已经有了发现
we had already found a couple.
而今天 通过超过30万科学爱好者的努力
And today, with the help of over 300,000 science enthusiasts,
我们已经发现了数十颗行星
we have found dozens,
而且我们发现了这一颗银河系中
and we’ve also found one of the most mysterious stars
最最奇异的恒星
in our galaxy.
为了说清楚
So to understand this,
请看一下开普勒数据中 一次正常的掩食是什么样子
let me show you what a normal transit in Kepler data looks like.
这幅图中左边轴是光强度
On this graph on the left-hand side you have the amount of light,
底下的横轴是时间
and on the bottom is time.
这条白线是单纯来自恒星的光
The white line is light just from the star,
天文学家称为光度曲线
what astronomers call a light curve.
现在当一颗行星掩过恒星 它阻挡了一点点星光
Now, when a planet transits a star, it blocks out a little bit of this light,
而这个掩食的深度 反映了行星体自身的大小
and the depth of this transit reflects the size of the object itself.
因此 例如木星
And so, for example, let’s take Jupiter.
行星通常不太会 比木星还要大
Planets don’t get much bigger than Jupiter.
木星会减弱百分之一的星光
Jupiter will make a one percent drop in a star’s brightness.
换做地球 地球只有木星的1/11大
Earth, on the other hand, is 11 times smaller than Jupiter,
它的信号在数据中几乎看不见
and the signal is barely visible in the data.
回到我们的谜题
So back to our mystery.
几年前 行星猎人正在筛选数据寻找掩食
A few years ago, Planet Hunters were sifting through data looking for transits,
他们发现了一个诡异的信号 来自恒星KIC 8462852
and they spotted a mysterious signal coming from the star KIC 8462852.
2009年五月是他们首次发现这个信号
The observations in May of 2009 were the first they spotted,
他们开始在论坛中讨论这个发现
and they started talking about this in the discussion forums.
他们说一个 类似木星的星体
They said and object like Jupiter
可以造成这样的星光削弱
would make a drop like this in the star’s light,
但他们也说这家伙太大了
but they were also saying it was giant.
你看 掩食通常只持续几个小时
You see, transits normally only last for a few hours,
而这一个持续了将近一周
and this one lasted for almost a week.
他们也在说谱线看起来不对称
They were also saying that it looks asymmetric,
这是说 不像木星那样有一个干净、U 型的负峰
meaning that instead of the clean, U-shaped dip that we saw with Jupiter,
大家看这条数据左侧的倾斜度很奇怪
it had this strange slope that you can see on the left side.
这似乎意味着
This seemed to indicate
无论闯进来挡住星光的是什么东西
that whatever was getting in the way and blocking the starlight
它不会像行星那样是个球形
was not circular like a planet.
后来陆续还有少量的负峰
There are few more dips that happened,
但这颗星在之后的一两年 一直都没什么动静
but for a couple of years, it was pretty quiet.
然后在2011年三月 我们观察到了这个
And then in March of 2011, we see this.
这颗恒星的光度 掉了整整15%!
The star’s light drops by a whole 15 percent,
这比一颗行星能造成的大太多了
and this is huge compared to a planet,
行星只能造成1%的光度下降
which would only make a one percent drop.
我们把这条谱线特征 描述为光滑和干净
We described this feature as both smooth and clean.
它也是不对称的
It also is asymmetric,
在持续近一周的时间内逐步减弱
having a gradual dimming that lasts almost a week,
然后在一两天内立马反弹回正常的光度
and then it snaps right back up to normal in just a matter of days.
在此之后 又是什么都没发生
And again, after this, not much happens
直到2013年二月
until February of 2013.
事情的发展完全出乎意料
Things start to get really crazy.
光度曲线上出现了一大群复杂的负峰
There is a huge complex of dips in the light curve that appear,
而且它们持续了差不多一百天
and they last for like a hundred days,
一直延续到开普勒计划结束
all the way up into the Kepler mission’s end.
这些负峰有着各种形状
These dips have variable shapes.
有一些很尖锐 有一些很宽
Some are very sharp, and some are broad,
以及有不同的持续时间
and they also have variable durations.
有一些只持续一两天 有的则超过一周
Some last just for a day or two, and some for more than a week.
而且在一些光度负峰中 还出现上上下下的起伏
And there’s also up and down trends within some of these dips,
感觉好像是几个独立事件重叠在一起
almost like several independent events were superimposed on top of each other.
而且这次 这颗恒星的亮度下降了超过20%
And at this time, this star drops in its brightness over 20 percent.
这说明不管是什么东西挡住了光
This means that whatever is blocking its light
这家伙有着超过地球1000倍的面积
has an area of over 1,000 times the area of our planet Earth.
这真心是非同寻常
This is truly remarkable.
当公民科学家发现这个时
And so the citizen scientists, when they saw this,
他们通知了科学家团队 称他们发现了足够奇怪的东西
they notified the science team that they found something weird enough
可能值得后续跟进研究
that it might be worth following up.
于是当科学家团队看过数据之后
And so when the science team looked at it,
我们觉得:好吧 会不会只是数据有点问题
we’re like, “Yeah, there’s probably just something wrong with the data.”
不过经过我们非常、 非常、非常仔细的调查
But we looked really, really, really hard,
数据没有问题
and the data were good.
因此 出现这些负峰一定有天体物理学的原因
And so what was happening had to be astrophysical,
说明太空中有什么东西 经过了我们和恒星之间
meaning that something in space was getting in the way
挡住了它的光
and blocking starlight.
这个时候
And so at this point,
我们竭力研究 关于这颗恒星的一切
we set out to learn everything we could about the star
希望能找到任何可以解释 这些现象的线索
to see if we could find any clues to what was going on.
帮助我们发现这颗星的公民科学家
And the citizen scientists who helped us in this discovery,
也加入了讨论
they joined along for the ride
见证科学第一线的行动
watching science in action firsthand.
首先 有人提出是不是这颗星非常年轻
First, somebody said, you know, what if this star was very young
它仍旧保有它诞生之时周围的星际云物质
and it still had the cloud of material it was born from surrounding it.
另外有人说
And then somebody else said,
好吧 是不是这颗星已经形成了行星系统
well, what if the star had already formed planets,
而两颗行星相撞了
and two of these planets had collided,
就像地球和月球的形成过程
similar to the Earth-Moon forming event.
好吧 这两种假说都可以解释部分数据
Well, both of these theories could explain part of the data,
但是困难在于 这颗恒星没有显示任何年轻的特征
but the difficulties were that the star showed no signs of being young,
而且也没有来自任何物质
and there was no glow from any of the material
被星光加热发出的光晕
that was heated up by the star’s light,
如果恒星年轻
and you would expect this if the star was young
或者碰撞产生大量尘埃 通常会出现这种现象
or if there was a collision and a lot of dust was produced.
又有人说
And so somebody else said,
好吧 会不会是一大群彗星呢
well, how about a huge swarm of comets
在一个非常椭圆的轨道上 一连串地穿过这颗恒星?
that are passing by this star in a very elliptical orbit?
好吧 这个假说倒是和我们的观测相吻合
Well, it ends up that this is actually consistent with our observations.
但是我同意 这感觉有点牵强
But I agree, it does feel a little contrived.
你看 需要数百颗彗星
You see, it would take hundreds of comets
才能重现我们的观测
to reproduce what we’re observing.
而这些只是
And these are only the comets
恰好从我们和恒星 中间穿过的彗星
that happen to pass between us and the star.
所以实际情况下 将会有成千上万颗彗星
And so in reality, we’re talking thousands to tens of thousands of comets.
但是在我们所有的烂解释中
But of all the bad ideas we had,
这个算是最好的了
this one was the best.
于是我们发表了我们的发现
And so we went ahead and published our findings.
要我说 这是我写过的最困难的论文之一
Now, let me tell you, this was one of the hardest papers I ever wrote.
科学家理应发表明确的结果
Scientists are meant to publish results,
而这次我们离结果还有十万八千里呢
and this situation was far from that.
所以我们决定起一个抓眼球的标题
And so we decided to give it a catchy title,
我们的题目是:《光去了哪里》
and we called it: “Where’s The Flux?”
麻烦大家自行意会这个梗
I will let you work out the acronym.
(笑声)
(Laughter)
不过这故事还没完呢
So this isn’t the end of the story.
在我写这篇论文的同时
Around the same time I was writing this paper,
我见了一位同行 贾森·莱特
I met with a colleague of mine, Jason Wright,
他也在写一篇有关开普勒数据的论文
and he was also writing a paper on Kepler data.
他说道:从开普勒无与伦比的精度来看
And he was saying that with Kepler’s extreme precision,
它其实可以探测到恒星周围的外星人建筑
it could actually detect alien megastructures around stars,
但是并没有发现
but it didn’t.
然后我给他看了 由我们公民科学家发现的奇怪数据
And then I showed him this weird data that our citizen scientists had found,
然后他对我说
and he said to me,
见鬼 塔碧
“Aw crap, Tabby.
这下我论文得重写了
Now I have to rewrite my paper.”
所以没错 自然解释很牵强
So yes, the natural explanations were weak,
我们很好奇
and we were curious now.
我们必须找到一个 排除外星人的方法
So we had to find a way to rule out aliens.
于是我俩一起说服了
So together, we convinced a colleague of ours
我们在SETI(寻找地外文明计划)工作的一位同行
who works on SETI, the Search for Extraterrestrial Intelligence,
说这是一个非常出色的追逐目标
that this would be an extraordinary target to pursue.
我们起草了一份观测这颗恒星的项目书
We wrote a proposal to observe the star
请求使用绿岸天文台的 世界上最大的射电天文望远镜
with the world’s largest radio telescope at the Green Bank Observatory.
两三个月后
A couple months later,
这份项目书的消息被媒体刺探到了
news of this proposal got leaked to the press
好吧 现在有几千篇报道
and now there are thousands of articles,
可能超过一万篇 单单关于这颗恒星
over 10,000 articles, on this star alone.
如果你用谷歌图片搜索
And if you search Google Images,
你会找到这些
this is what you’ll find.
现在观众可能会问:好吧塔碧
Now, you may be wondering, OK, Tabby, well,
究竟怎么用外星人去解释这光度曲线?
how do aliens actually explain this light curve?
好吧 想象一个远比我们发达的文明
OK, well, imagine a civilization that’s much more advanced than our own.
在这个假设条件下
In this hypothetical circumstance,
这个文明肯定耗尽了他们母星的能源
this civilization would have exhausted the energy supply of their home planet,
所以他们从哪里获取更多的能量?
so where could they get more energy?
你看 他们有一颗宿主恒星 就像我们有太阳一样
Well, they have a host star just like we have a sun,
那如果他们能够 从恒星中抓取更多能量
and so if they were able to capture more energy from this star,
那就可以解决他们的能源需求
then that would solve their energy needs.
所以他们可能会去建造这些巨型建筑
So they would go and build huge structures.
这些巨大的超级建筑
These giant megastructures,
比如巨大的太阳能电池板叫做“戴森球”
like ginormous solar panels, are called Dyson spheres.
上面这些图片
This image above
是许多艺术家想象中的戴森球
are lots of artists’ impressions of Dyson spheres.
很难去想象这些东西究竟有多庞大
It’s really hard to provide perspective on the vastness of these things,
但你可以这么想
but you can think of it this way.
地球到月球间的距离是四十万公里
The Earth-Moon distance is a quarter of a million miles.
这些巨型结构中的最简单的单元
The simplest element on one of these structures
是100倍地月距离
is 100 times that size.
它们是庞然大物
They’re enormous.
再想象 这样一个建筑围绕着一颗恒星运动
And now imagine one of these structures in motion around a star.
你可以看到这为什么可以造成数据中异常
You can see how it would produce anomalies in the data
如此不对称 不自然的负峰
such as uneven, unnatural looking dips.
然而即使是外星人的超级建筑
But it remains that even alien megastructures
也不能违反物理定律
cannot defy the laws of physics.
任何使用大量能量的东西
You see, anything that uses a lot of energy
将会产生热量
is going to produce heat,
我们却没有观测到
and we don’t observe this.
但这有可能只是非常简单的
But it could be something as simple
他们把热量释放到了另一个方向
as they’re just reradiating it away in another direction,
没有对着地球
just not at Earth.
我个人最喜欢的另一种可能性是
Another idea that’s one of my personal favorites
我们恰好目睹了一场星球大战
is that we had just witnessed an interplanetary space battle
一颗行星被灾难性地彻底摧毁了
and the catastrophic destruction of a planet.
我承认这会产生很多尘埃
Now, I admit that this would produce a lot of dust
然而我们没有观测到
that we don’t observe.
但是如果我们已经在用外星人来解释
But if we’re already invoking aliens in this explanation,
那谁说他们不会秋风扫落叶一般清理干净尘埃
then who is to say they didn’t efficiently clean up all this mess
回收利用?
for recycling purposes?
(笑声)
(Laughter)
你看这很快就激发想象力啦
You can see how this quickly captures your imagination.
好啦 故事就是这样
Well, there you have it.
我们的处境是
We’re in a situation that could unfold
既可以解释成 我们没搞清楚的自然现象
to be a natural phenomenon we don’t understand
又可以解释成 我们没搞清楚的外星人科技
or an alien technology we don’t understand.
作为科学家 我个人还是会赌这是个自然现象
Personally, as a scientist, my money is on the natural explanation.
但是别误解了 我绝对认同能找到外星人非常棒
But don’t get me wrong, I do think it would be awesome to find aliens.
不管怎样 会有新东西、非常有趣的东西等待发现
Either way, there is something new and really interesting to discover.
那么接下来呢?
So what happens next?
我们需要继续观测这颗恒星
We need to continue to observe this star
去更详细地了解发生了什么
to learn more about what’s happening.
然而像我这样的职业天文学家
But professional astronomers, like me,
我们在这方面的资源有限
we have limited resources for this kind of thing,
而开普勒望远镜已经在执行另一项计划了
and Kepler is on to a different mission.
所以我很高兴地说:又一次
And I’m happy to say that once again,
公民科学家加入进来救场
citizen scientists have come in and saved the day.
你看 这次
You see, this time,
业余天文爱好者拿着他们的业余望远镜
amateur astronomers with their backyard telescopes
立刻加入进来开始在自己的观测点
stepped up immediately and started observing this star nightly
夜观此星
at their own facilities,
我非常期待他们的发现
and I am so excited to see what they find.
对我来说 激动人心的是这颗恒星可能根本不会被电脑发现
What’s amazing to me is that this star would have never been found by computers
因为我们单纯没有把这样的恒星当成目标
because we just weren’t looking for something like this.
更令人兴奋的是
And what’s more exciting
将来还有更多的数据
is that there’s more data to come.
有新的观测项目要上马
There are new missions that are coming up
准备观测百万颗恒星
that are observing millions more stars
布满全天
all over the sky.
思考一下:如果我们又找到一颗这样的恒星 意味着什么?
And just think: What will it mean when we find another star like this?
而如果我们一颗都没找到 那又意味着什么?
And what will it mean if we don’t find another star like this?
谢谢
Thank you.
(鼓掌)
(Applause)

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视频概述

天鹅座KIC8462852是比太阳更大的恒星,距离地球大约有1480光年,最近被发现,曾出现过大规模光强衰减,其幅度远超正常行星凌星情况。是什么挡住超过20%的光线!是科学仪器出错了吗?这到底意味着什么?假如你没看过三体,不妨看看这里的故事

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收集自网络

翻译译者

Ljimnn

审核员

赖皮

视频来源

https://www.youtube.com/watch?v=gypAjPp6eps

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