Age of the Infrared The Sky at Night

Good evening.

On this programme, we're going to talk about far-infrared astronomy

and some people won't know what that means.

What is far infrared?

Well, here we have three experts -

Chris Lintott, Chris North and John Richer.

They cover almost the whole field of astronomy,

which I most certainly do not.

So, here they are. Good evening.

Good evening, Patrick. I'm delighted to be talking about the infrared,

because we can use it to look at the really cool stuff in the universe, by which I mean cold, of course.

That seems a little counter intuitive but it makes some sense.

We're used to looking at the universe with our eyes,

we're used to getting visible light through telescopes and cameras.

But we are biased towards the bits of the universe that shine,

whether they're stars or even lightbulbs that shine

and give out optical light.

Most of the stuff we can see here,

yourself, the table, even our guests here,

we see them because they are reflecting that light.

But they're also shining, they're shining in infrared.

One way to think about that is to imagine a red hot coal.

It will be giving off faint light

but if you hold your hands out to the coal, you can feel heat.

That heat is because of infrared radiation, just a longer wavelength form of the light.

We can demonstrate this by playing with an infrared camera, Chris.

Yes, so here we have a camera that's showing at the moment,

Patrick in the infrared.

So what we can see here is light Patrick is giving off.

We can see that the yellow stuff is warmer

and, Patrick, you have a cold nose.

And a cold monocle.

-Yes.

-And also, a very black cat.

Yes, so the picture of Ptolemy the cat in the infrared.

We can scan this around the room.

You can see that the things that are normally hidden are now seen -

the camera crew and the lights are glowing in the infrared.

And here we have John as well.

-Very warm.

-Not quite as cold a nose as Patrick.

You can see this is a different view of the world from the visible universe

because we have two mugs here that look pretty identical,

filled with water and they look the same in the optical,

but in the infrared, Chris?

The one on the left is certainly black, so it is very cold

and the one on the right is white hot.

This is filled with hot water from the kettle, this is iced water.

That's something you can't tell using optical light.

You need the infrared or to pick them up

and one of the problems with astronomy is, it's difficult to pick things up.

It is indeed.

What do we see when we point an infrared -

or even a longer wavelength - telescope at the sky?

The key difference from the optical, where we see stars,

the hot things in the universe,

we see the bits of the universe which are cold.

So between the stars, which is largely empty space,

there are clouds of gas and dust.

They come in various forms but ones that are particularly interesting

are called molecular clouds.

In these clouds is a collection of molecules and dust particles.

They are only maybe 10 degrees above absolute zero.

-That's -273 Celsius.

-Yes.

These molecular clouds typically are at -263 degrees Celsius,

or 10 degrees above absolute zero.

Then there are little molecules

in the clouds, different molecular species,

and they rotate at different rates.

They make jumps between different rotational states.

When they do that, they emit little packets of light

at particular distinct frequencies.

The infrared telescope doesn't look like an ordinary telescope?

Tell us about the James Clerk Maxwell Telescope, JCMT?

Yes, the JCMT's a telescope that has been operating now

on a remote mountain top in Hawaii for over 20 years now.

It's a reflecting dish,

a large reflecting telescope, 15m diameter.

At the focus are these special far-infrared cameras

that detect far-infrared radiation,

a bit like the one demonstrated here.

The really difficult thing is the detector has to be cold itself

because otherwise all you see is the camera.

Yes. The newest camera is called SCUBA-2

It's a very new project.

And inside there, there's a very large far-infrared camera

that's cooled to only one-tenth of a degree above absolute zero.

We should explain why the pictures look so terrible.

For people used to looking at Hubble pictures,

the visible, we're into the science of blobology here.

Why is it so hard to get a decent image at these wavelengths?

In far infrared, wavelengths are longer than in the optical.

So although we have a 15-metre telescope,

the resolution of the images we get isn't very good.

The resolution of the James Clerk Maxwell Telescope

is very similar to that of the unaided human eye.

It's quite good, in terms of our daily lives,

but in terms of detail for the study of astronomy,

it's not good enough for many of the observations we want to make.

Nonetheless, what can we see, for example, if we point it at M17?

What we know is that, in these large molecular clouds,

new generations of stars are forming as we speak.

So by mapping the large structures in these molecular clouds,

we can find where the new stars are forming.

To take a very close look, we're going to need a different telescope

and luckily, there's one being built.

It's the most ambitious international collaboration in astronomical history.

The telescope is called ALMA. It's down in Chile.

A few years ago, I went to look at the site.

Not much there then but things are pretty different now.

ALMA was designed to work in the same part of the spectrum -

the very far infrared as we observe with SCUBA-2 -

but it was to address the fundamental problem with SCUBA-2.

It's great for seeing big things in the universe

and surveying where all the stars are forming,

what we can't do is zoom in and look in very great detail.

-ALMA can do that?

-Yes. So, obviously the JCMT is a 15-metre dish

and we worked out that to look at the detail

we need a dish that's 15 km in size.

Now, clearly, that's impossible to build.

A bit difficult to steer!

Yes! And way beyond our budget!

We utilise the technique of radio interferometry.

We recognise that, in fact, you don't need to build all the dish,

the mirror, to make a good image.

You can build parts of the mirror in different places.

So, in this case, we've got a 15-kilometre-sized plateau

up high in the Chilean Andes

and we have 66 separate radio antennas,

which are spread around the site,

and we take the signals from each of those antennas

and combine them in an electronic focus, if you like.

From that electronic focus we can make images

and it's as if our telescope had a diameter of 15 kilometres.

So that means that images are 1,000 times more detailed than the JCMT.

And so, for the first time, we actually now have, getting with ALMA,

images that can compete, in resolution terms,

with optical images, which is something that,

I think, infrared astronomers

have always been very jealous of optical astronomers! So we've talked about the technology

and how complex it is and there's a lot of work going in around the world

to build these, and some of that is taking place in the UK.

I went to the Rutherford Appleton Laboratory in Oxfordshire to find out more.

The Rutherford Appleton Laboratory has a worldwide reputation

for building fabulous astronomical instruments

which end up on telescopes all over the world.

High in the Chilean desert,

the ALMA telescopes are looking at the cold part of the sky

and to do that, they need to be kept as cool as can be.

Telescope dishes are big and impressive

but they're just light buckets.

It's the scientific instruments,

the unsung heroes at the back of the telescopes,

which do the hard work. It's their job

to receive light collected by the dish

and turn it into the amazing scientific results and images

which will wow us.

At the Rutherford Appleton Laboratory, Professor Brian Ellison

is helping build the space-age refrigerators

which will help keep the instruments cool.

It's a chance for me to immerse myself totally

in super-conducting tunnel junctions and local oscillators.

Just my kind of fun!

So, Brian, we've got in front of us

the heart of one of the receivers of ALMA.

Tell us what we're seeing here.

OK, this is one of the super-conducting

tunnel-junction receivers of ALMA

that detects the energy from the telescope focus.

What happens is that the signal from the telescope comes down through,

bounces off various mirrors here

and is brought to another focus at the detector, here.

This device works at four degrees kelvin - four degrees above absolute zero -

and picks up the energy, and that propagates down these cables here,

at a frequency of about 4GHz,

out through various components,

it's amplified down through the rest of the structure

and out to the outside world.

So, this is one of the receivers,

and there are quite a few in each cryostat.

So if we look at the back of here,

-we've got quite a range of them.

-Yes.

Here is the rear end of the ALMA receiver system.

What you're seeing here is an array

of the different local oscillator assemblies

that provide the receiver reference signals.

So we've got light coming in from the sky,

compared with this reference source that comes in from the back,

they're mixed at that detector we just saw

and the resulting signal is fed out the back?

The result's being fed out the back. Basically, it's a radio receiver

but working at a much higher frequency than the average radio.

So far, 16 of these space-age receivers

have been fitted to telescopes on the Chajnantor Plateau,

with 50 more to follow over the coming year.

The ALMA telescope has already started giving us

an amazing view of the Antennae galaxies.

In visible light, we see two galaxies

which are in the process of colliding,

each containing billions of stars.

With ALMA's ultra-cold eyes, we see the gas and dust between the stars,

providing our first detailed view of the galactic crumple zone

in which new stars are forming.

ALMA is sure to amaze us even more over the years and decades to come,

proving that it's cool to be infrared.

We've been talking about telescopes on the ground.

What about telescopes in space?

Of course, so far,

the most ambitious infrared telescope in space is Herschel.

Herschel's been up for three years.

It's the best far-infrared telescope we've got up in space.

It's looking at wavelengths

that are slightly warmer stuff than SCUBA-2 and ALMA,

but one key thing is,

these are wavelengths that are impossible to observe from the ground

-because the atmosphere is, essentially, opaque over most of the range.

-Yes.

So, take the Pillars Of Creation from Hubble.

It's one of the most iconic images.

Dust clouds against a bright background.

Oh, they're amazing things, yes.

The optical light we're seeing

is gas on the edges of these three fingers that are being energised,

or ionised, by starlight from some nearby young stars.

But if you look in the infrared, you're not seeing the gas,

you're seeing the dust itself glowing.

And what you can tell, from the temperature of the dust,

you can see how many stars are heating the dust up

and then you can see some very cold clumps.

These are the stars that are starting to form.

One of the interesting things about star formation

is that the coldest things we know of in the universe

are about to become the hottest things we know of in the universe!

So we can see much more about where stars are forming and the environments they are forming in.

But it can also look at enormous areas.

You can get images with 6,000 galaxies in.

The images are typically a few times the width of the moon across

but if you take something that's the size

of your little finger held at arm's length,

there's still a thousand-odd galaxies in there.

These are at times when the universe was only a few billion years old.

One of the things Herschel can uniquely do is allow us to study water in the universe.

Now, even in Chile on that very dry site,

there's enough water in the atmosphere to block out the signals

from water molecules emitting in these clouds.

-It's not impressive to discover water in Earth's atmosphere.

-No, that's right, but Herschel,

being above the atmosphere, with it's very specialised receiver,

can tune to some of the frequencies

when the water molecules change their rotational state,

and we can get these spectra of water in star-forming regions.

The results are surprising, right?

To a large extent, we've detected less water than expected

based on models, so there's a mystery there

to really understand the whole process by which water forms.

We know it HAS to form, in quite large abundances,

but the signals so far have been

somewhat weaker than we're expecting.

We've been talking about Herschel as one of the best infrared space telescopes.

There's another one up there which is also very impressive

and it's called the WISE satellite.

That's been looking at slightly different wavelengths

and I went to speak to one of the lead scientists, Amy Mainzer.

NASA's big infrared mission, WISE, was designed to map the cosmos

and also to discover new objects that no other telescope could see.

It could only work for a year,

but in that short time it collected an amazing amount of information.

'Whilst in Nantes, France, I caught up with one of the team, Amy Mainzer.'

-We collected millions of pictures.

-Sure.

We took a picture every 11 seconds for a year

with a four-megapixel camera,

so you can imagine that that builds up a lot of data very quickly.

So imagine trying to go through that slideshow! It would take a while.

Hiding in the dark and amidst all that data, was a strange object,

and the WISE team found it - a new type of star.

One of the most fun things that we've discovered

so far with WISE is something called a brown dwarf,

and it's a new class of brown dwarf that is actually room temperature.

This is a star that can't even boil water.

At its surface it's about room temperature - very cool -

and it's basically kind of like

a more massive version of Jupiter, if you will.

These are things that are sort of halfway between the stars and the planets.

They're probably more like a planet in some ways than a star.

-OK.

-And the processes going on in their core

-are not quite the same as what goes on in a star like the sun.

-Right.

Some people call brown dwarfs failed stars.

They are not very good at being stars because they can't fuse hydrogen into helium.

What makes our sun glow is gravity is so powerful at the centre,

it can take two hydrogen atoms and jam them together to make a helium.

That releases a lot of energy

but brown dwarfs just don't have the mass.

They can't do it. They cannot make helium.

-The density isn't high enough in the centre.

-Just not enough.

So they're kind of like wimpier versions of our sun. Lots wimpier!

What happens is, when they form,

as they collapse out of a cloud of gas and dust,

they get hot in the middle but, unlike our sun,

which then starts to shine of its own accord through fusion,

these guys just cool off.

You can see these with WISE,

and you're finding them surprisingly close.

Right. One of the things we're really interested in doing

is seeing are there stars that are as close as the ones

we know to be closest?

Maybe there are stars that are even closer.

So the search is on, we're hunting through these images right now

to cull out things that look like they might be these very cold,

very nearby brown dwarf stars.

WISE has also been searching the cold, dark depths

of our own solar system, hunting for asteroids.

In particular, ones that could threaten Earth.

We were actually able to observe

more than 157,000 asteroids in our solar system.

That's about a quarter of the known population.

Most of these are in the main belt

between Mars and Jupiter but we were also able to independently discover 33,000 so far

-and that number keeps changing as more and more observations connect to other people's.

-OK.

-And you're analysing your data again and again?

-That's right.

One of the fun things is it's constantly changing.

It's a fast-paced field - keeps us busy!

Most asteroids stay in the main belt,

-but some stray.

-As of today we know of about 8,000 near-Earth objects

that have been discovered by observers all over the world, going back hundreds of years.

Today we have with WISE a different and unique sample,

in the sense that because we observed these objects with infrared light,

we were able to get really good measurements of sizes of asteroids.

Mostly they look for visible light,

so sunlight bouncing off the surface,

-so they depend a lot on how reflective the surface is.

-Right.

That makes it hard to tell the difference between something

small but bright and large but dark.

Yes, a lot of these things,

-like comets, are made of ice and therefore shiny.

-Yes.

There's a huge amount of diversity in all asteroids and comets.

Just look at the average rocks you see on Earth.

There's just as much diversity among asteroids.

If we have both infrared and visible light, not only can we measure

the sizes very well but also how much sunlight is reflected off the surface.

So WISE had to be cool

to work and that meant, eventually, the coolant ran out.

-That's right.

-So that part of its mission ended.

Yes. The mission is now in honourable retirement.

It completed all its mission goals and then some.

We completed an extended mission and now we're done.

The survey part is done and now we're processing the data.

Big missions like WISE leave long legacies,

and it will take many decades for astronomers to sift through

the millions of images it has taken.

Who knows what further discoveries will be made?

WISE has finished its mission now but it was great to hear about it

and the data will be useful. It does raise the question, John,

how do you see these different surveys,

on different scales, at different wavelengths,

how do they come together?

We're very lucky to have Herschel up and flying and operating

and ALMA coming online simultaneously.

It's by putting data together from those that we learn most

and build up the spectral energy distribution of the object.

So by building physical models of these objects and comparing them with the data,

we can work out exactly how stars form.

Let's say we gather here again in, what, let's say five years' time.

Alma will be up and running. What do you think the big discoveries will have been?

We already know there are

lots and lots of extrasolar planets out there,

so we know we have to have a way of forming those.

So my hope, I suppose, for Alma is

that over the next five, ten years of observing,

we make good enough images of protoplanetary discs

to really understand the details of how exactly stars form,

where and when they form and how they maybe migrate through the disc to their current locations.

Well, it's all fascinating stuff.

John, Chris, Chris, thank you very much.

So let's go now into my garden, where we find Pete and Paul

also looking at the infrared sky.

I think any chance of seeing stars tonight is wishful thinking.

-Look at all the cloud.

-It's a bit of a problem, isn't it?

-There's a thick blanket of cloud up there.

-Depressing.

It looks pretty uniform when we look at it visually,

but I have a very special camera here, which is an infrared camera.

It's sensitive to the mid-infrared range.

And when you point that one up to the sky, it can see clouds as well.

Right. That's brilliant - a useful device!

But, unlike when we're looking at the sky visually,

seeing it as a uniform blanket of cloud,

we can pick out structure in it looking through this camera,

so it's good for picking out holes in the cloud.

-I gather it's on me at the moment, so it can pick out my velvet jacket.

-It can.

-Basically, it's picking out all the different temperatures of your body as well.

-The cold, cold hands.

-It actually looks like you've got sunglasses on.

-They're reflective.

But the problem with infrared,

if you're trying to look at stuff in the sky which is emitting infrared,

is the Earth's atmosphere, the water vapour in the Earth's atmosphere.

And that means that, for amateur astronomy,

we have a bit of a problem, because unless we get rid of the atmosphere,

we can't see anything in those ranges. But there are things we can do,

mainly in the area of planetary imaging.

On that subject, we have a little story.

-I don't know if you're familiar with the Ashen Light.

-Oh, yes.

-It was seen by Giovanni Riccioli on January 9th 1643.

-Right.

And he noticed that there was this faint light on the dark side,

the night side of Venus. It kind of looks a little bit like Earthshine.

That's the effect when you get a really thin crescent moon

-in the evening or morning twilight.

-That's right.

And that's caused by reflected light from the Earth.

Of course, that can't possibly be the case with Venus.

Really nothing to do with it on Venus. It's a very vague thing.

Sometimes it covers the whole of the dark side of Venus

and other times just portions of it.

It's a sort of greenish glow, very subtle.

I know you are quite sceptical. You've got that look in your face.

"I don't believe a word of it. It's just visual, people seeing things."

I think there is a genuine phenomenon there.

There are a hell of a lot of reports about the Ashen Light.

The problem is that when you have a crescent Venus,

it looks like it really wants to complete the circle.

I'm very open-minded. I'm quite happy if somebody comes along

and says, "There's the Ashen Light, there it is," I'll be happy to accept that, obviously.

But I have tried and tried, using near-infrared filters,

because that's where it's supposed to be at its brightest,

pushing the crescent of Venus off the side of the frame

and upping the sensitivity of the camera,

and I've picked nothing up.

Tell you what, I'll bet with you within the next decade

that it will have shown to be a genuine phenomenon.

A decade's an awfully long time. OK, let's go for it.

-You've witnessed this.

-What do I win?

-Respect.

THEY LAUGH

But Venus isn't the only thing we can do with infrared.

-You've used it with Mars and Jupiter, haven't you?

-Yeah.

Basically, you use a near-infrared filter.

When you look through one of these filters, it has the effect,

because you're using a longer wavelength

than the normal visual part of the spectrum,

the seeing is a bit steadier.

So that helps us if we're trying to take high-resolution images

of, particularly, Mars, Jupiter,

Saturn and the moon,

because it allows us to get a much more steady view of these things.

But also, the infrared actually starts to crisp up,

it gives a greater contrast on some features,

particularly with Mars, because Mars is a very reddish planet.

So those albedo features are exaggerated.

-They stand out brilliantly, actually.

-Good.

Sticking with Venus,

-there's an interesting conjunction in March with Jupiter.

-Yes, that's right,

because Venus is moving away from the sun

and Jupiter is marching in towards the evening twilight.

So they'll have an encounter.

They will have an encounter, which is called a conjunction,

and that will occur or be at its best in the middle of March.

That's going to be pretty spectacular,

because you've got two really bright planets.

Venus is the brightest of all.

I think Mars can get marginally brighter than Jupiter.

-Yeah, but not this time of year.

-No.

But when they're together, they're going to look like an amazing,

really bright double star.

-You're going to be out photographing them, aren't you?

-Of course.

It would be lovely to add some of these images to our Flickr site,

-so if anybody does any infrared stuff or captures the Ashen Light...

-Yeah, it'd be absolutely amazing.

If you want to see all our lovely pictures,

go to our BBC Flickr site, which is located at...

All these wonderful objects in February and March, Pete -

-aren't we lucky?

-We are indeed.

We've moved in from my garden with the two Chrises.

First of all, this picture of the Helix Nebula,

-and it's infrared and it's a lovely picture.

-It's a wonderful image,

Patrick, in the infrared from the VISTA telescope down in Chile.

It really shows the interaction between the gas,

which is the outer layers of a sun-like star

near the end of its life that's been shed,

and the star itself.

You can see these dusty rings of different layers,

then you see these fingers which are being illuminated by the central star.

-It's an incredible image and a beautiful object.

-Another thing that's near the sun

and has survived so far is a sun-grazing comet.

This comet goes by the name Comet Lovejoy,

named after Terry Lovejoy,

who discovered it at the end of last year.

And it went incredibly close to the sun.

It went within about 140,000 kilometres of the sun,

incredibly close and hot.

You would expect a comet that goes that close to be broken up

and to evaporate, and that's what was expected to happen as this comet went past the sun,

then miraculously, it came out the other side intact.

So it must have been much bigger than it was previously thought,

-to have survived the encounter.

-Some of the images are gorgeous. We can see this glorious comet.

Why couldn't this have happened in the north of the sky?

-Why didn't it come closer to the Earth?

-This is just not fair, but a beautiful comet nonetheless.

I hadn't realised that all of these sun-grazer comets, most of them

are supposed to come from the break-up of a single larger body

not that long ago,

so we're seeing the dying embers of a past massive comet. Rather wonderful.

Well now, also, yet more tenants of other stars.

I'm getting a bit tired of these.

Well, these are exciting ones.

I know what you mean, but our last programme was on exoplanets,

and we just caught the discovery

of the first unambiguously Earth-sized and Venus-sized worlds.

But it's been topped already,

and we have three Mars-sized bodies.

They were able to be detected because they're close to their parent star.

And so we're really getting down to rocky planets now,

and they too, I think, will turn out to be common.

In fact, we have a survey that used a technique called microlensing,

looking for the bending of light from distant stars.

A team looking at this microlensing data predicted this week

that there are probably 100 billion planets, at least, in our galaxy,

so you're going to be bored of them for a while yet, Patrick.

Many of those must contain life. I wonder, what is life?

Well, let's hope they're watching.

But let's come back to your province, let's leave life alone

for this month and talk about the moon, because there's a new NASA mission.

-Yes, and an interesting one, too.

-Yes, this is a mission called GRAIL.

'Zero, and liftoff of the Delta 2 with GRAIL,

'journey to the centre of the moon.'

It's two spacecraft.

They're going to fly in immense precision around the moon,

and as they do so, as they pass over massive regions, they will dip,

and as they pass over less dense regions, they will rise

just by the differences of the moon's gravity.

By doing that, they plan to map the interior of the whole moon

and we'll get a sense of how the moon formed.

And it will tell us about why the near side of the moon

is so different from the far side.

We think that's because of how the moon formed. Hopefully the GRAIL satellites, which have been renamed

by some students in America who won a competition...

Instead of GRAIL A and GRAIL B, they're now called Ebb and Flow.

THEY LAUGH

-Oh, dear! And with that, I think we'll say good night!

-Yes.

I'll be back next week,

this time talking about amateur astronomers and the work they do in astronomy,

which, believe me, is really considerable.

So, for now, from all of us, good night.

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