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射电望远镜是怎样给我们展示肉眼见不到的宇宙的

How radio telescopes show us unseen galaxies | Natasha Hurley-Walker

宇宙
Space, the final frontier.
无穷无尽我六岁的时候就听到
I first heard these words when
了这样的话
I was just six years old,
这激励了我
and I was completely inspired.
我想探索新奇的世界
I wanted to explore strange new worlds.
新的生命
I wanted to seek out new life.
我想了解宇宙中的每一件事物
I wanted to see everythingthat the universe had to offer.
带着这些梦想 这些信念我就踏上了追梦旅程
And those dreams, those words,they took me on a journey,
一个读书 上大学 读博士
a journey of discovery, through school, through university,
最后成为一个专业的天文学家的旅程
to do a PhD and finallyto become a professional astronomer. Now,
目前为止 我了解了两件有趣的事情
I learned two amazing things,
第一件有点令我小伤心 当我读博士的时候
one slightly unfortunate, when I was doing my PhD.
我才知道 实际上
I learned that the reality was
我以后根本不能驾驶宇宙飞船
I wouldn’t be pilotinga starship anytime soon.
但是我同时也了解到宇宙是
But I also learned that the universe is strange,
奇妙、壮观、广阔的
wonderful and vast,
实际上宇宙太大 大到用宇宙飞船根本不可能探索得完
actually too vastto be explored by spaceship.
所以我把注意力转移到了天文学
And so I turned my attentionto astronomy, to using telescopes. Now,
用望远镜来探索宇宙 在你们展开想象之前我先给大家展示一下星空吧
I show you before you an image of the night sky.
在世界的任何地方都能看到这样的景象
You might see it anywhere in the world.
这些星体是我们星系的一部分
And all of these stars are part of our local galaxy,
银河系
the Milky Way. Now,
现在如果你看一看
if you were to
夜空中黑暗的部分
go to a darker part of the sky,
选一个好地方观察 沙漠就行
a nice dark site, perhaps in the desert,
你也许会看到银河的中心
you might see the centerof our Milky Way galaxy
上千亿的星体在你面前散布着
spread out before you,hundreds of billions of stars.
景象极其壮观
And it’s a very beautiful image.
五彩斑斓当然
It’s colorful.
这只是我们宇宙的一个局部的中心
And again, this is justa local corner of our universe.
许多奇怪的黑色尘埃分散其中
You can see there’s a sort of strange dark dust across it. Now,
这些是局部尘埃 他们阻挡了其他星体发出来的光线
that is local dust that’s obscuring the light of the stars.
但是我们做的还不错
But we can do a pretty good job.
仅仅用肉眼
Just with our own eyes,
我们就能探索宇宙的一个小角落
we can explore our little corner of the universe.
所以我们有进步的余地
It’s possible to do better.
你可以用神奇的哈勃空间望远镜(来探索宇宙)
You can use wonderful telescopeslike the Hubble Space Telescope. Now,
现在天文学家已经把收集到的景象放在一起
astronomershave put together this image.
叫做哈勃深空视场
It’s called the Hubble Deep Field,
他们花数百个小时
and they’ve spent hundreds
观察这一小块天空
of hours observing just a tiny patch of the sky
相当于比你整条胳膊上的一小块
no larger than your thumbnailheld at arm’s length.
指甲还小的地方 在这个景象中 你可以看到上千个星系
And in this image you can see thousands of galaxies,
我们知道在整个宇宙
and we know that there must be hundreds
中一定还存在
of millions, billions of galaxies
上亿的星系 一些星系跟我们的星系相似另一些和我们的完全不同
in the entire universe, some like our own and some very different.
所以你就想着 没问题啊我可以继续研究
So you think, OK, well,I can continue this journey.
很简单 我只要有一个足够牛的望远镜就行
This is easy. I can justuse a very powerful telescope
然后再拿它看看天空
and just look at the sky, no problem.
没问题的 实际上 如果我们真的这么做的话就什么都探索不到了
It’s actually really missing outif we just do that. Now,
因为我们到目前为止所说的一切
that’s becauseeverything I’ve talked about so far
仅仅是用可见光看到的
is just using the visible spectrum,
你们的眼睛就可以看到
just the thing that your eyes can see,
这只是宇宙中
and that’s a tiny slice,
很小的一部分
a tiny, tiny slice of what the universe has to offer us. Now,
非常非常小而且现在就可见光来说 我们也有两个非常重要的问题需要解决
there’s also two very importantproblems with using visible light.
现在不仅不能研究那些
Not only are we missing outon all the other processes
发出其他不可见光的东西
that are emitting other kinds of light,
(在可见光范围内)我们也有两个问题
but there’s two issues. Now,
第一个是我之前提到的尘埃
the first is that dustthat I mentioned earlier.
这些尘埃阻挡了可见光我们看不到后边的东西
The dust stops the visible lightfrom getting to us.
所以我们进一步探索宇宙的话光线就比之前更少
So as we look deeper into the universe, we see less light.
尘埃阻挡了光线
The dust stops it getting to us.
在研究宇宙的过程中 我们在如何应用
But there’s a really strange problemwith using visible light
可见光方面也有问题
in order to try and explore the universe.
我们先不说这个
Now take a break for a minute.
假设你现在站在喧闹大街的角落 很热闹
Say you’re standing on a corner,a busy street corner.
大街上的车川流不息
There’s cars going by.
这时候一辆救护车正驶来
An ambulance approaches.
警报器发出尖锐的声音
It has a high-pitched siren.
(模仿警报声呼啸而过)
(Imitates a siren passing by)
在警报器靠近你之后又远离你的过程中
The siren appeared to change in pitch
它的声调似乎在改变
as it moved towards and away from you.
救护车司机不是为了引起你的注意而改变声调的
The ambulance driver did not change the siren just to mess with you.
而是你自身的感觉造成的
That was a product of your perception.
随着救护车的靠近
The sound waves,as the ambulance approached,
波长变短 所以声调变高
were compressed, and they changed higher in pitch.
之后救护车远离我们 波长变长
As the ambulance receded,the sound waves were stretched,
所以听起来声调比较低
and they sounded lower in pitch.
光线同样是如此
The same thing happens with light.
当物体靠近我们的时候
Objects moving towards us,
光波波长变得短 它们看起来更蓝
their light waves are compressedand they appear bluer.
当物体远离我们的时候
Objects moving away from us,
波长变长 它们看起来更红
their light waves are stretched,and they appear redder.
我们称此为光波的蓝移效应和红移效应
So we call these effectsblueshift and redshift. Now,
我们的宇宙在不断扩张
our universe is expanding,
所以事物之间在彼此远离
so everything is moving awayfrom everything else,
这就意味着 在我们看来 所有的事物都在向红移的方向发展
and that meanseverything appears to be red.
有趣的是 你越向宇宙深处看
And oddly enough, as you lookmore deeply into the universe,
远处的物体移动的就越快越远
more distant objectsare moving away further and faster,
他们看起来就越红
so they appear more red.
所以我们回到哈勃深空视场
So if I come back to the Hubble Deep Field
通过哈勃望远镜
and we were to continueto peer deeply into the universe
看向宇宙深处
just using the Hubble,
我们看得越远
as we get to a certain distance away,
事物在我们的视线中就越红 这就出现问题了
everything becomes red, and that presents something of a problem. Eventually,
实际上在更远处
we get so far away
所有的东西都转换成了红外线
everything is shifted into the infrared
我们根本什么都看不看到
and we can’t see anything at all.
所以这个问题必须要解决
So there must be a way around this. Otherwise,
否则我就被困住了
I’m limited in my journey.
在红移效应困扰我之前
I wanted to explore the whole universe,
我想探索的是全宇宙
not just whatever I can see, you know,
并不只是我用肉眼看到的
before the redshift kicks in.
我们有一项技术
There is a technique.
叫做射电天文学
It’s called radio astronomy.
天文学家已经应用了十几年
Astronomers have beenusing this for decades.
这是个非常有趣的技术
It’s a fantastic technique.
这个是帕克斯射电望远镜我们亲切的叫它“盘子”
I show you the Parkes Radio Telescope,affectionately known as”The Dish.”
你们也许看过这个电影
You may have seen the movie.
无线电简直棒极了
And radio is really brilliant.
它让我们进一步探索宇宙
It allows us to peer much more deeply.
我们不用被那些尘埃遮挡视线了
It doesn’t get stopped by dust,
所以你可以看到宇宙中的任何事物
so you can see everything in the universe,
红移效应的问题也不
and redshift is less
那么棘手了 因为我们有接收器能够接受穿过岩石的射线
of a problem because we can build receivers that receive across a large band.
所以我们用帕克斯
So what does Parkes see when we turn
看向宇宙中心的时候
it to the center of the Milky Way?
能看到一些有趣的东西对吧
We should see something fantastic, right? Well,
我们的确看到了一些有趣的东西
we do see something interesting.
那些尘埃看不到了
All that dust has gone.
就像我之前说的 无线电穿过了尘埃
As I mentioned, radio goes straight through dust, so not a problem.
所以问题解决了 但是景象却变得不一样了
But the view is very different.
我们能看到银河的
We can see that the center
中心在闪烁
of the Milky Way is aglow,
这些并不是星光
and this isn’t starlight.
这种光叫做同步加速器辐射
This is a light calledsynchrotron radiation,
来自宇宙磁场周围旋转的电子
and it’s formed from electronsspiraling around cosmic magnetic fields.
所以这一平面里的光线就会闪烁
So the plane is aglow with this light.
我们也能够看到奇怪的成团的东西
And we can also seestrange tufts coming off of it,
以及在我们肉眼看起来
and objects which don’t appear to line up
分散、
with anything that we can seewith our own eyes.
没有序列的东西 我很难分析这个图像
But it’s hard to reallyinterpret this image,
因为很明显 它的分辨率非常低
because as you can see,it’s very low resolution.
射电具有很长的波长
Radio waves have a wavelength that’s long,
使其分辨率更低
and that makes their resolution poorer.
而且这个图像还是黑白的
This image is also black and white,
所以我们不知道那些景象
so we don’t really know what is the color of everything in here. Well,
到底是什么颜色的 快进到当下
fast-forward to today.
我们建造的望远镜 能克服这些问题了
We can build telescopes which can get over these problems. Now,
这是来默奇森射电
I’m showing you
天文观测台的照片
here an image of the Murchison Radio Observatory,
这是一个建造射电望远镜的好地方
a fantastic placeto build radio telescopes.
很平坦 很干燥
It’s flat, it’s dry,
最重要的是 不受其他无线电的干扰
and most importantly, it’s radio quiet:
没有移动电话 没有无线网 什么都没有
no mobile phones, no Wi-Fi, nothing,
十分十分清净
just very, very radio quiet,
作为搭建射电望远镜的地方堪称完美
so a perfect placeto build a radio telescope. Now,
现在这个我已经
the telescope
使用好几年的望远镜
that I’ve been working on for a few years
叫做默奇森广角阵列
is called the Murchison Widefield Array,
这是它一点点建造的过程
and I’m going to show you a little time lapse
这是
of it being built.
一群在珀斯的大学本科生和
This is a group of undergraduateand postgraduate students
研究生我们
located in Perth.
叫他们学生军
We call them the Student Army,
他们牺牲自己的时间来建造这个射电望远镜
and they volunteered their time to build a radio telescope.
没有课程学分
There’s no course credit for this.
这些学生把偶极子组装起来
And they’re putting togetherthese radio dipoles.
它们能像调频收音机或者
They just receive at low frequencies,
电视一样接收低频信号
a bit like your FM radio or your TV.
我们把它们建在了沙漠里
And here we are deploying themacross the desert.
最后一部分占澳大利亚西部沙漠的
The final telescopecovers 10 square kilometers
10平方公里
of the Western Australian desert.
有趣的是 它们不能移动
And the interesting thing is,there’s no moving parts.
我们把这些小天线
We just deploy these little antennas
放在在六角形的网上
essentially on chicken mesh.
成本相当的低
It’s fairly cheap.
天线上的电缆 接收信号
Cables take the signals from the antennas
然后把信号传递给中央处理器
and bring themto central processing units.
这样的望远镜遍布整个沙漠
And it’s the size of this telescope,
它的占地面积使它在处理问题能力的方面
the fact that we’ve built it over the entire desert
比帕克斯的望远镜更好
that gives us a betterresolution than Parkes. Now,
所有的电缆最后汇成一股
eventually all those cablesbring them to a unit
把信息传递到珀斯的一个超级计算机上
which sends it offto a supercomputer here in Perth,
那就是我要工作的部分
and that’s where I come in.
(叹气)
(Sighs)
研究无线电数据
Radio data.
过去五年的时间
I have spent the last five years working
我一直在研究这些困难却有趣
with very difficult, very interesting data
之前没有人了解过的数据
that no one had really looked at before.
我在这个超级计算机上花了
I’ve spent a long time calibrating it,
数以百万计的CPU时数校对
running millions of CPU hourson supercomputers
并试图弄清楚这些数据
and really trying to understand that data.
通过这套望远镜 这些数据
And with this telescope, with this data,
我们对整个南半球的星空做了一番仔细观察
we’ve performed a survey of the entire southern sky,
银河系及超银河系默奇森广角阵列全天候研究
the GaLactic and ExtragalacticAll-sky MWA Survey,
或者简称GLEAM
or GLEAM, as I call it.
我非常兴奋
And I’m very excited.
这个研究结果快要公之于世了
This survey is just about to be published,
但是目前还没有
but it hasn’t been shown yet,
所以你们还算是第一批了解这些
so you are literally the first people to
关于南半球星空研究的人
see this southern survey of the entire sky.
我也很高兴分享给你们研究中的部分图像
So I’m delighted to share with you some images from this survey. Now,
现在 请想象一下你们就在默奇森
imagine you went to the Murchison,
在满天星斗下露营
you camped out underneath the stars
你抬头仰望南部星空
and you looked towards the south.
看到了南极 看到银河在上升
You saw the south’s celestial pole, the galaxy rising.
如果我让射电光弱一点
If I fade in the radio light,
就会看到我们研究中所观察到的景象
this is what we observe with our survey.
你会看到银河不再黑乎乎的充满尘埃
You can see that the galactic plane is no longer dark with dust.
它被星空中数以千计的点点
It’s alight with synchrotron radiation,
和同步加速器辐射点亮
and thousands of dots are in the sky.
广袤的 靠近我们星系的麦哲伦云
Our large Magellanic Cloud,our nearest galactic neighbor,
其实是橘色的 而不是接近蓝白色的
is orange insteadof its more familiar blue-white.
这里面有很多的东西值得研究
So there’s a lot going on in this.
让我们放大看一下
Let’s take a closer look.
如果我们想想看我刚刚给你们展示的
If we look backtowards the galactic center,
帕克森拍摄的银河中心的景象
where we originally saw the Parkes image
低分辨率
that I showed you earlier,
黑白色的
low resolution, black and white,
然后再看GLEAM的图像
and we fade to the GLEAM view,
你们会发现这个分辨率提升了一百倍
you can see the resolution has gone up by a factor of a hundred.
我们看到的是充满色彩的星空
We now have a color view of the sky,
五彩斑斓这些
a technicolor view. Now,
颜色并不是有偏差的颜色
it’s not a false color view.
他们是真正的无线电波发射出来的颜色
These are real radio colors.
我们已经实现把低频率的显示成红色
What I’ve done is I’ve coloredthe lowest frequencies red
把高频率的显示成蓝色 中间频率偏绿色
and the highest frequencies blue, and the middle ones green.
这就给我们呈现了五颜六色的景象
And that gives us this rainbow view.
这些也不仅仅是伪色
And this isn’t just false color.
这个图片里的颜色是在显示
The colors in this imagetell us about the physical processes
宇宙中事物的物理过程
going on in the universe.
举个例子
So for instance,
如果你看向银河的一个平面
if you look along the plane of the galaxy,
同步加速器使它变亮 呈现出带鲜红的橙色画面
it’s alight with synchrotron, which is mostly reddish orange,
但是我们仔细再看一下我们会看到蓝色的点
but if we look very closely,we see little blue dots. Now,
现在 我们再放大 这些蓝色的点实际上就是离子化等离子体
if we zoom in, these blue dots are ionized plasma
它们在明亮的星体周围
around very bright stars,
并且挡住了红色光线
and what happens is that they block the red light,
所以它们看起来是蓝色的
so they appear blue.
我们通过这些可以知道在我们银河中
And these can tell usabout these star-forming regions
形成星体的地方
in our galaxy.
并且一下子就能看出来
And we just see them immediately.
因为当我们望向宇宙
We look at the galaxy,
颜色就会告诉我们它们在那儿
and the color tells us that they’re there.
你们还能在这一银河平面中看到
You can see little soap bubbles,
小的肥皂泡一样的圆形图像
little circular images around the galactic plane,
这些是超新星残余物
and these are supernova remnants.
当一个星体爆炸的时候 它的外表壳就会被炸开
When a star explodes, its outer shell is cast off
然后这颗星体会飘忽在宇宙中聚合其他的物质
and it travels outward into spacegathering up material,
由此形成新的小的保护壳
and it produces a little shell.
对天文学家来讲那些超新星残余物的去向
It’s been a long-standingmystery to astronomers
一直是一个神秘的过程
where all the supernova remnants are.
我们都知道在宇宙空间中
We know that there must be a lot
一定有许多高能电子
of high-energy electrons in the plane
它们产生我们所看见的同步加速器辐射
to produce the synchrotronradiation that we see,
我们认为它们是由超新星残余物产生的
and we think they’re producedby supernova remnants,
但是它们看起来好像还不是很多
but there don’t seem to be enough. Fortunately,
幸运的是 GLEAM能够非常非常准确的探测到超新星残余物
GLEAM is really, reallygood at detecting supernova remnants,
所以我们有望于这一方面研究成果的产生
so we’re hoping to have a new paper out on that soon. Now,
好 我们再继续说
that’s fine.
我们已经探索了我们的局部宇宙
We’ve explored our little local universe,
但是我想更进一步的探索 深入研究
but I wanted to go deeper,I wanted to go further.
我想探索银河以外的宇宙
I wanted to go beyond the Milky Way. Well,
现在在图片的右上方
as it happens,
我们能够看到一个很有意思的东西
we can see a very interesting object in the top right,
这是局部电波星系
and this is a local radio galaxy,
半人马座A
Centaurus A.
如果我们放大来看
If we zoom in on this,
我们能够看到两片巨大的羽毛一样的东西
we can see that there are two huge plumes going out into space.
然后你们再看两片羽毛的中间
And if you look right in the center

between those two plumes,
会看到和一个我们银河很像的星系
you’ll see a galaxy just like our own.
它是螺旋状的 有一条尘埃带
It’s a spiral. It has a dust lane.
就是一个普通的星系
It’s a normal galaxy.
但是这些星点只能在无线电中才能看到
But these jetsare only visible in the radio.
如果我们用肉眼看的话
If we looked in the visible,
根本不知道它们在那里
we wouldn’t even know they were there,
他们比主星系还要大上千倍
and they’re thousands of times largerthan the host galaxy.
那么发生了什么这些星点是从
What’s going on?What’s producing these jets?
哪里来的呢 我们都知道每个星系中心
At the center of every galaxythat we know about
都有一个超级大的黑洞
is a supermassive black hole. Now,
黑洞是不可见的这就是为什么叫做黑洞
black holes are invisible.That’s why they’re called that.
你们能看见的只有它们周围改变
All you can see is the deflection
轨迹的光线
of the light around them,
当一颗星体或者一团星云
and occasionally, when a star or a cloud
进入其轨道
of gas comes into their orbit,
就会被潮汐力分裂
it is ripped apart by tidal forces,
形成我们所说的吸积盘
forming what we call an accretion disk.
吸积盘在X光下很明亮
The accretion diskglows brightly in the x-rays,
并且巨大的磁场可以让物质
and huge magnetic fieldscan launch the material into space
以光速进入宇宙空间
at nearly the speed of light.
所以这些星点对无线电可见
So these jets are visible in the radio
这就是我们的研究成果
and this is what we pick up in our survey. Well,
所以我们现在看到的是一个电波星系 很不错
very well, so we’ve seenone radio galaxy. That’s nice.
但是我们再看最上方
But if you just lookat the top of that image,
也有一个电波星系
you’ll see another radio galaxy.
这个就小一点了
It’s a little bit smaller,
因为离我们较远好了
and that’s just because it’s further away. OK.
两个星系了
Two radio galaxies.
我们能够看到这样 很不错了
We can see this. This is fine. Well,
那么剩下那些点怎么办呢
what about all the other dots?
你们可能会觉得那些就是星体
Presumably those are just stars.
但你们错了
They’re not.
那些都是电波星系
They’re all radio galaxies.
每一个在这上面成点状的
Every single one of the dots in this image
都是一个遥远的星系 离我们数十亿光年远
is a distant galaxy, millions to billions of light-years away
这些星系的中心也是把物质以光速
with a supermassiveblack hole at its center
甩进宇宙空间的黑洞
pushing material into spaceat nearly the speed of light.
很令人兴奋
It is mind-blowing.
我展示的只是研究成果的冰山一角
And this survey is even largerthan what I’ve shown here.
如果我把整个研究成果都展示出来
If we zoom out tothe full extent of the survey,
你会看到30万个这样的无线电星系
you can see I found 300,000of these radio galaxies.
的确是个费劲的活儿
So it’s truly an epic journey.
我们对所有这些星系的
We’ve discovered all of these galaxies
研究都追溯到了最早的超质量黑洞
right back to the very firstsupermassive black holes.
我很为之自豪下周研究成果就会公开
I’m very proud of this, and it will be published next week. Now,
这还不是全部
that’s not all.
我已经探究了迄今为止宇宙的最深处
I’ve explored the furthest reachesof the galaxy with this survey,
但在这幅图像之外还有很多信息
but there’s somethingeven more in this image. Now,
现在我们回顾一下时间伊始
I’ll take you right backto the dawn of time.
宇宙形成之时经历了大爆炸
When the universe formed,it was a big bang,
留下一片氢的汪洋
which left the universeas a sea of hydrogen,
中性氢
neutral hydrogen.
当第一个星系形成的时候
And when the very first starsand galaxies switched on,
它们把氢气电离了
they ionized that hydrogen.
所以宇宙从中性不带电
So the universe wentfrom neutral to ionized.
变成了电离的了 我们周围就产生了电信号
That imprinted a signal all around us. Everywhere,
无形中像力一样渗透到了 我们周围
it pervades us, like the Force. Now,
因为这是很长很长以前发生的事情了
because that happened so long ago,
现在那些信号已经红移了 所以是低频的
the signal was redshifted, so now that signal is at very low frequencies.
和我研究的是一样的频率
It’s at the same frequency as my survey,
但是这频率太微弱了
but it’s so faint.
是我们研究的物体频率的十亿分之一
It’s a billionth the size of any of the objects in my survey.
所以我们的望远镜并不能很灵敏的探索到这些信号
So our telescope may not be quite sensitive enough to pick up this signal. However,
然而 又有了新的射电望远镜
there’s a new radio telescope.
所以虽然我不能乘坐宇宙飞船
So I can’t have a starship,
但是我很高兴拥有 世界上最大的射电望远镜
but I can hopefully have one of the biggest radio telescopes in the world.
我们正在建平方公里阵列射电望远镜一个新的射电望远镜
We’re building the Square Kilometre Array,a new radio telescope,
比默契森广角
and it’s going to be
阵列还大上千倍
a thousand times bigger than the MWA,
灵敏上千倍 效果也更好
a thousand times more sensitive,and have an even better resolution.
所以我们会发现数千万的星系
So we should findtens of millions of galaxies.
或许再深入研究那些信号
And perhaps, deep in that signal,
我们会发现宇宙
I will get to look
中形成的第一颗星体和星系
upon the very first stars and galaxies switching on,
以及时间诞生的那一刻
the beginning of time itself.
谢谢
Thank you.
(掌声
(Applause)

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