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

Transcriber: Joseph Geni Reviewer: Joanna Pietrulewicz

翻译人员: 罗 昕竺 校对人员: Wei Wu

宇宙，无穷无尽

Space, the final frontier.

I first heard these words when I was just six years old,

我六岁的时候就听到了这样的话

and I was completely inspired.

这激励了我

I wanted to explore strange new worlds.

我想探索新奇的世界

新的生命

I wanted to seek out new life.

I wanted to see everything that the universe had to offer.

我想了解宇宙中的每一件事物

And those dreams, those words, they took me on a journey,

带着这些梦想，这些信念 我就踏上了追梦旅程

a journey of discovery,

一个读书

上大学，读博士

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 finally to become a professional astronomer.

Now, I learned two amazing things,

目前为止，我了解了两件有趣的事情

one slightly unfortunate,

第一件有点令我小伤心

when I was doing my PhD.

当我读博士的时候

I learned that the reality was

我才知道，实际上

我以后根本不能驾驶宇宙飞船

I wouldn't be piloting a starship anytime soon.

But I also learned that the universe is strange, wonderful and vast,

但是我同时也了解到宇宙是 奇妙、壮观、广阔的

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 vast to be explored by spaceship.

And so I turned my attention to astronomy, to using telescopes.

所以我把注意力转移到了天文学 用望远镜来探索宇宙

Now, I show you before you an image of the night sky.

在你们展开想象之前 我先给大家展示一下星空吧

You might see it anywhere in the world.

在世界的任何地方 都能看到这样的景象

And all of these stars are part of our local galaxy, the Milky Way.

这些星体是我们星系的一部分，银河系

Now, if you were to go to a darker part of the sky,

现在如果你看一看夜空中黑暗的部分

a nice dark site, perhaps in the desert,

选一个好地方观察，沙漠就行

you might see the center of our Milky Way galaxy

你也许会看到银河的中心

spread out before you, hundreds of billions of stars.

上千亿的星体在你面前散布着

And it's a very beautiful image.

景象极其壮观

It's colorful.

五彩斑斓

And again, this is just a local corner of our universe.

当然，这只是我们宇宙的 一个局部的中心

You can see there's a sort of strange dark dust across it.

许多奇怪的黑色尘埃分散其中

Now, that is local dust

这些是局部尘埃

that's obscuring the light of the stars.

他们阻挡了其他星体发出来的光线

But we can do a pretty good job.

但是我们做的还不错

仅仅用肉眼，我们就能 探索宇宙的一个小角落

Just with our own eyes, we can explore our little corner of the universe.

It's possible to do better.

所以我们有进步的余地

You can use wonderful telescopes like the Hubble Space Telescope.

你可以用神奇的哈勃空间望远镜 （来探索宇宙）

Now, astronomers have put together this image.

现在天文学家已经把 收集到的景象放在一起

It's called the Hubble Deep Field,

叫做哈勃深空视场

and they've spent hundreds of hours observing just a tiny patch of the sky

他们花数百个小时观察这一小块天空

no larger than your thumbnail held at arm's length.

相当于比你整条胳膊上的一小块 指甲还小的地方

And in this image

在这个景象中

you can see thousands of galaxies,

你可以看到上千个星系

and we know that there must be hundreds of millions, billions of galaxies

我们知道在整个宇宙中一定还存在

in the entire universe,

上亿的星系

some like our own and some very different.

一些星系跟我们的星系相似 另一些和我们的完全不同

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.

This is easy. I can just use a very powerful telescope

很简单，我只要有一个 足够牛的望远镜就行

and just look at the sky, no problem.

然后再拿它看看天空，没问题的

It's actually really missing out if we just do that.

实际上，如果我们真的这么做的话 就什么都探索不到了

因为我们到目前为止所说的一切

Now, that's because everything I've talked about so far

is just using the visible spectrum, just the thing that your eyes can see,

仅仅是用可见光看到的， 你们的眼睛就可以看到，

and that's a tiny slice,

这只是宇宙中

很小的一部分，非常非常小

a tiny, tiny slice of what the universe has to offer us.

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

Now, there's also two very important problems with using visible light.

Not only are we missing out on all the other processes

现在不仅不能研究那些

that are emitting other kinds of light,

发出其他不可见光的东西

but there's two issues.

（在可见光范围内） 我们也有两个问题

Now, the first is that dust that I mentioned earlier.

第一个是我之前提到的尘埃

The dust stops the visible light from getting to us.

这些尘埃阻挡了可见光 我们看不到后边的东西

So as we look deeper into the universe, we see less light.

所以我们进一步探索宇宙的话 光线就比之前更少

The dust stops it getting to us.

尘埃阻挡了光线

But there's a really strange problem with using visible light

在研究宇宙的过程中，我们在如何应用

in order to try and explore the universe.

可见光方面也有问题

Now take a break for a minute.

我们先不说这个

Say you're standing on a corner, a busy street corner.

假设你现在站在 喧闹大街的角落，很热闹

大街上的车川流不息

There's cars going by.

An ambulance approaches.

这时候一辆救护车正驶来

It has a high-pitched siren.

警报器发出尖锐的声音

(Imitates a siren passing by)

（模仿警报声呼啸而过）

在警报器靠近你之后 又远离你的过程中

The siren appeared to change in pitch

as it moved towards and away from you.

它的声调似乎在改变

The ambulance driver did not change the siren just to mess with you.

救护车司机不是为了 引起你的注意而改变声调的

而是你自身的感觉造成的

That was a product of your perception.

The sound waves, as the ambulance approached,

随着救护车的靠近

were compressed,

波长变短

and they changed higher in pitch.

所以声调变高

As the ambulance receded, the sound waves were stretched,

之后救护车远离我们，波长变长

and they sounded lower in pitch.

所以听起来声调比较低

The same thing happens with light.

光线同样是如此

当物体靠近我们的时候

Objects moving towards us,

their light waves are compressed and they appear bluer.

光波波长变得短，它们看起来更蓝

Objects moving away from us,

当物体远离我们的时候

their light waves are stretched, and they appear redder.

波长变长，它们看起来更红

So we call these effects blueshift and redshift.

我们称此为光波的蓝移效应和红移效应

Now, our universe is expanding,

我们的宇宙在不断扩张

so everything is moving away from everything else,

所以事物之间在彼此远离

and that means everything appears to be red.

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

有趣的是，你越向宇宙深处看

And oddly enough, as you look more deeply into the universe,

more distant objects are moving away further and faster,

远处的物体移动的就越快越远

他们看起来就越红

so they appear more red.

So if I come back to the Hubble Deep Field

所以我们回到哈勃深空视场

and we were to continue to peer deeply into the universe

通过哈勃望远镜

just using the Hubble,

看向宇宙深处

as we get to a certain distance away,

我们看得越远

everything becomes red,

事物在我们的视线中就越红

and that presents something of a problem.

这就出现问题了

Eventually, we get so far away

实际上在更远处

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.

So there must be a way around this.

所以这个问题必须要解决

Otherwise, I'm limited in my journey.

否则我就被困住了

I wanted to explore the whole universe,

在红移效应困扰我之前

我想探索的是全宇宙 并不只是我用肉眼看到的

not just whatever I can see, you know, before the redshift kicks in.

我们有一项技术

There is a technique.

It's called radio astronomy.

叫做射电天文学

Astronomers have been using this for decades.

天文学家已经应用了十几年

这是个非常有趣的技术

It's a fantastic technique.

I show you the Parkes Radio Telescope, affectionately known as "The Dish."

这个是帕克斯射电望远镜 我们亲切的叫它“盘子”

你们也许看过这个电影

You may have seen the movie.

And radio is really brilliant.

无线电简直棒极了

It allows us to peer much more deeply.

它让我们进一步探索宇宙

我们不用被那些尘埃遮挡视线了

It doesn't get stopped by dust,

so you can see everything in the universe,

所以你可以看到宇宙中的任何事物

红移效应的问题也不那么棘手了

and redshift is less of a problem

because we can build receivers that receive across a large band.

因为我们有接收器 能够接受穿过岩石的射线

So what does Parkes see when we turn it to the center of the Milky Way?

所以我们用帕克斯 看向宇宙中心的时候

能看到一些有趣的东西对吧

We should see something fantastic, right?

我们的确看到了一些有趣的东西

Well, we do see something interesting.

那些尘埃看不到了

All that dust has gone.

As I mentioned, radio goes straight through dust, so not a problem.

就像我之前说的， 无线电穿过了尘埃，所以问题解决了

But the view is very different.

但是景象却变得不一样了

We can see that the center of the Milky Way is aglow,

我们能看到银河的中心在闪烁

and this isn't starlight.

这些并不是星光

This is a light called synchrotron radiation,

这种光叫做同步加速器辐射

and it's formed from electrons spiraling around cosmic magnetic fields.

来自宇宙磁场周围旋转的电子

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 see strange tufts coming off of it,

and objects which don't appear to line up

以及在我们肉眼看起来

分散、没有序列的东西

with anything that we can see with our own eyes.

But it's hard to really interpret this image,

我很难分析这个图像

because as you can see, it's very low resolution.

因为很明显，它的分辨率非常低

Radio waves have a wavelength that's long,

射电具有很长的波长

and that makes their resolution poorer.

使其分辨率更低

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 到底是什么颜色的

so we don't really know what is the color of everything in here.

Well, fast-forward to today.

快进到当下，

我们建造的望远镜

We can build telescopes

which can get over these problems.

能克服这些问题了

这是来默奇森射电天文观测台的照片

Now, I'm showing you here an image of the Murchison Radio Observatory,

a fantastic place to build radio telescopes.

这是一个建造射电望远镜的好地方

很平坦，很干燥

It's flat, it's dry,

and most importantly, it's radio quiet:

最重要的是，不受其他无线电的干扰

no mobile phones, no Wi-Fi, nothing,

没有移动电话，没有无线网，什么都没有

just very, very radio quiet,

十分十分清净

so a perfect place to build a radio telescope.

作为搭建射电望远镜的地方堪称完美

Now, the telescope that I've been working on for a few years

现在这个我已经使用好几年的望远镜

is called the Murchison Widefield Array,

叫做默奇森广角阵列

and I'm going to show you a little time lapse of it being built.

这是它一点点建造的过程

This is a group of undergraduate and postgraduate students

这是一群在珀斯的大学本科生和

研究生

located in Perth.

We call them the Student Army,

我们叫他们学生军

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.

There's no course credit for this.

没有课程学分

And they're putting together these radio dipoles.

这些学生把偶极子组装起来

它们能像调频收音机或者 电视一样接收低频信号

They just receive at low frequencies, 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 them across the desert.

最后一部分占澳大利亚西部沙漠的

The final telescope covers 10 square kilometers

of the Western Australian desert.

10平方公里

And the interesting thing is, there's no moving parts.

有趣的是，它们不能移动

We just deploy these little antennas

我们把这些小天线

放在在六角形的网上

essentially on chicken mesh.

It's fairly cheap.

成本相当的低

Cables take the signals

天线上的电缆

接收信号

from the antennas

然后把信号传递给中央处理器

and bring them to central processing units.

And it's the size of this telescope,

这样的望远镜遍布整个沙漠

the fact that we've built it over the entire desert

它的占地面积使它在 处理问题能力的方面

that gives us a better resolution than Parkes.

比帕克斯的望远镜更好

Now, eventually all those cables bring them to a unit

所有的电缆最后汇成一股

which sends it off to a supercomputer here in Perth,

把信息传递到珀斯的 一个超级计算机上

那就是我要工作的部分

and that's where I come in.

(Sighs)

（叹气）

Radio data.

研究无线电数据

I have spent the last five years

过去五年的时间

working with very difficult, very interesting data

我一直在研究这些困难却有趣

that no one had really looked at before.

之前没有人了解过的数据

I've spent a long time calibrating it,

我在这个超级计算机上花了

running millions of CPU hours on supercomputers

数以百万计的CPU时数校对

and really trying to understand that data.

并试图弄清楚这些数据

And with this telescope,

通过这套望远镜

with this data,

这些数据

we've performed a survey of the entire southern sky,

我们对整个南半球的 星空做了一番仔细观察

the GaLactic and Extragalactic All-sky MWA Survey,

银河系及超银河系默奇森 广角阵列全天候研究

or GLEAM, as I call it.

或者简称GLEAM

And I'm very excited.

我非常兴奋

This survey is just about to be published, but it hasn't been shown yet,

这个研究结果快要公之于世了 但是目前还没有

so you are literally the first people

所以你们还算是第一批了解这些

to see this southern survey of the entire sky.

关于南半球星空研究的人

So I'm delighted to share with you some images from this survey.

我也很高兴分享给你们 研究中的部分图像

Now, imagine you went to the Murchison,

现在，请想象一下你们就在默奇森

you camped out underneath the stars

在满天星斗下露营

and you looked towards the south.

你抬头仰望南部星空

You saw the south's celestial pole,

看到了南极

the galaxy rising.

看到银河在上升

If I fade in the radio light,

如果我让射电光弱一点

this is what we observe with our survey.

就会看到我们研究中所观察到的景象

You can see that the galactic plane is no longer dark with dust.

你会看到银河不再黑乎乎的充满尘埃

It's alight with synchrotron radiation,

它被星空中数以千计的点点

and thousands of dots are in the sky.

和同步加速器辐射点亮

Our large Magellanic Cloud, our nearest galactic neighbor,

广袤的，靠近我们星系的麦哲伦云

is orange instead of its more familiar blue-white.

其实是橘色的，而不是接近蓝白色的

这里面有很多的东西值得研究 让我们放大看一下

So there's a lot going on in this. Let's take a closer look.

If we look back towards the galactic center,

如果我们想想看我刚刚给你们展示的

帕克森拍摄的银河中心的景象

where we originally saw the Parkes image that I showed you earlier,

low resolution, black and white,

低分辨率，黑白色的

and we fade to the GLEAM view,

然后再看GLEAM的图像

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,

a technicolor view.

五彩斑斓

Now, it's not a false color view.

这些颜色并不是有偏差的颜色

These are real radio colors.

他们是真正的无线电波发射出来的颜色

What I've done is I've colored the lowest frequencies red

我们已经实现把低频率的显示成红色

and the highest frequencies blue,

把高频率的显示成蓝色

中间频率偏绿色

and the middle ones green.

And that gives us this rainbow view.

这就给我们呈现了五颜六色的景象

And this isn't just false color.

这些也不仅仅是伪色

这个图片里的颜色是在显示

The colors in this image tell us about the physical processes

宇宙中事物的物理过程

going on in the universe.

So for instance, if you look along the plane of the galaxy,

举个例子，如果你看向银河的一个平面

it's alight with synchrotron,

同步加速器使它变亮

呈现出带鲜红的橙色画面

which is mostly reddish orange,

but if we look very closely, we see little blue dots.

但是我们仔细再看一下 我们会看到蓝色的点

Now, if we zoom in,

现在，我们再放大

these blue dots are ionized plasma

这些蓝色的点实际上就是离子化等离子体

around very bright stars,

它们在明亮的星体周围

and what happens is that they block the red light,

并且挡住了红色光线

so they appear blue.

所以它们看起来是蓝色的

And these can tell us about these star-forming regions

我们通过这些可以知道在我们银河中

in our galaxy.

形成星体的地方

并且一下子就能看出来

And we just see them immediately.

We look at the galaxy, and the color tells us that they're there.

因为当我们望向宇宙 颜色就会告诉我们它们在那儿

You can see little soap bubbles,

你们还能在这一银河平面中看到

little circular images around the galactic plane,

小的，肥皂泡一样的圆形图像

and these are supernova remnants.

这些是超新星残余物

When a star explodes,

当一个星体爆炸的时候

its outer shell is cast off

它的外表壳就会被炸开

and it travels outward into space gathering up material,

然后这颗星体会飘忽在宇宙中 聚合其他的物质

由此形成新的小的保护壳

and it produces a little shell.

It's been a long-standing mystery to astronomers

对天文学家来讲 那些超新星残余物的去向

一直是一个神秘的过程

where all the supernova remnants are.

We know that there must be a lot of high-energy electrons in the plane

我们都知道在宇宙空间中 一定有许多高能电子

to produce the synchrotron radiation that we see,

它们产生我们所看见的 同步加速器辐射

我们认为它们是由超新星残余物产生的

and we think they're produced by supernova remnants,

but there don't seem to be enough.

但是它们看起来好像还不是很多

Fortunately, GLEAM is really, really good at detecting supernova remnants,

幸运的是，GLEAM能够非常非常准确的 探测到超新星残余物

so we're hoping to have a new paper out on that soon.

所以我们有望于 这一方面研究成果的产生

Now, that's fine.

好，我们再继续说

我们已经探索了我们的局部宇宙

We've explored our little local universe,

but I wanted to go deeper, I wanted to go further.

但是我想更进一步的探索，深入研究

I wanted to go beyond the Milky Way.

我想探索银河以外的宇宙

Well, as it happens, we can see a very interesting object in the top right,

现在在图片的右上方我们能够看到 一个很有意思的东西

and this is a local radio galaxy,

这是局部电波星系

Centaurus A.

半人马座A

If we zoom in on this,

如果我们放大来看

we can see that there are two huge plumes going out into space.

我们能够看到两片巨大的羽毛一样的东西

And if you look right in the center between those two plumes,

然后你们再看两片羽毛的中间

you'll see a galaxy just like our own.

你会看到和一个我们银河很像的星系

It's a spiral. It has a dust lane.

它是螺旋状的，有一条尘埃带

It's a normal galaxy.

就是一个普通的星系

但是这些星点只能在无线电中才能看到

But these jets are only visible in the radio.

If we looked in the visible, we wouldn't even know they were there,

如果我们用肉眼看的话 根本不知道它们在那里

and they're thousands of times larger than the host galaxy.

他们比主星系还要大上千倍

What's going on? What's producing these jets?

那么发生了什么 这些星点是从哪里来的呢

我们都知道每个星系中心

At the center of every galaxy that we know about

is a supermassive black hole.

都有一个超级大的黑洞

黑洞是不可见的 这就是为什么叫做黑洞

Now, black holes are invisible. That's why they're called that.

你们能看见的只有 它们周围改变轨迹的光线

All you can see is the deflection of the light around them,

当一颗星体或者一团星云进入其轨道

and occasionally, when a star or a cloud of gas comes into their orbit,

it is ripped apart by tidal forces,

就会被潮汐力分裂

forming what we call an accretion disk.

形成我们所说的吸积盘

The accretion disk glows brightly in the x-rays,

吸积盘在X光下很明亮

and huge magnetic fields can launch the material into space

并且巨大的磁场可以让物质

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.

所以我们现在看到的是 一个电波星系，很不错

Well, very well, so we've seen one radio galaxy. That's nice.

但是我们再看最上方

But if you just look at 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，因为离我们较远

It's a little bit smaller, and that's just because it's further away.

OK. Two radio galaxies.

好了，两个星系了

We can see this. This is fine.

我们能够看到这样，很不错了

那么剩下那些点怎么办呢

Well, what about all the other dots?

Presumably those are just stars.

你们可能会觉得那些就是星体

They're not.

但你们错了

那些都是电波星系

They're all radio galaxies.

Every single one of the dots in this image

每一个在这上面成点状的

都是一个遥远的星系

is a distant galaxy,

millions to billions of light-years away

离我们数十亿光年远

with a supermassive black hole at its center

这些星系的中心也是把物质以光速

pushing material into space at nearly the speed of light.

甩进宇宙空间的黑洞

很令人兴奋

It is mind-blowing.

And this survey is even larger than what I've shown here.

我展示的只是研究成果的冰山一角

If we zoom out to the full extent of the survey,

如果我把整个研究成果都展示出来

你会看到30万个这样的无线电星系

you can see I found 300,000 of these radio galaxies.

的确是个费劲的活儿

So it's truly an epic journey.

We've discovered all of these galaxies

我们对所有这些星系的

right back to the very first supermassive black holes.

研究都追溯到了最早的超质量黑洞

I'm very proud of this, and it will be published next week.

我很为之自豪 下周研究成果就会公开

这还不是全部

Now, 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 reaches of the galaxy with this survey,

but there's something even more in this image.

但在这幅图像之外还有很多信息

Now, I'll take you right back to the dawn of time.

现在我们回顾一下时间伊始

When the universe formed, it was a big bang,

宇宙形成之时经历了大爆炸

which left the universe as a sea of hydrogen,

留下一片氢的汪洋

neutral hydrogen.

中性氢

And when the very first stars and galaxies switched on,

当第一个星系形成的时候

they ionized that hydrogen.

它们把氢气电离了

So the universe went from neutral to ionized.

所以宇宙从中性不带电 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, it pervades us,

无形中像力一样渗透到了

like the Force.

我们周围

Now, because that happened so long ago,

因为这是很长很长以前发生的事情了

the signal was redshifted,

现在那些信号已经红移了

so now that signal is at very low frequencies.

所以是低频的

It's at the same frequency as my survey,

和我研究的是一样的频率

but it's so faint.

但是这频率太微弱了

It's a billionth the size of any of the objects in my survey.

是我们研究的物体频率的十亿分之一

So our telescope may not be quite sensitive enough to pick up this signal.

所以我们的望远镜并不能很灵敏的 探索到这些信号

然而，又有了新的射电望远镜

However, there's a new radio telescope.

So I can't have a starship,

所以虽然我不能乘坐宇宙飞船

but I can hopefully have

但是我很高兴拥有

one of the biggest radio telescopes in the world.

世界上最大的射电望远镜

We're building the Square Kilometre Array, a new radio telescope,

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

and it's going to be a thousand times bigger than the MWA,

比默契森广角阵列还大上千倍

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 find tens of millions of galaxies.

或许，再深入研究那些信号

And perhaps, deep in that signal,

I will get to look upon the very first stars and galaxies switching on,

我们会发现宇宙中形成的 第一颗星体和星系

以及时间诞生的那一刻

the beginning of time itself.

Thank you.

谢谢

（掌声）

(Applause)