Stunning Saturn The Sky at Night

This month, we are at the Harwell Space Cluster, near Oxford,

home to some of the biggest names in the exploration of our universe.

There is the European Space Agency,

the Rutherford Appleton Laboratory,

and Chris and I have been invited

to the new Satellite Applications Catapult,

who are building business links to astronomy and space science.

Tonight's programme is all about Saturn, one of the first things

I saw through a telescope and still my favourite planet.

Saturn is famous for its fantastic rings, but there is so much more

to this mysterious planet, including its very strange moons.

Chris North is here too,

and he'll be answering some of your Space Surgery questions.

And because Saturn is so well placed in the night sky at the minute,

Peter and Paul have headed off to Hampshire

to see if they can catch a glimpse.

Oh, my word! Look at that.

I think that's the best view I've had of Saturn all night.

Yeah, I think you're absolutely right.

Spectacular Saturn,

out amongst the stars of Virgo.

The reason we have such amazing images of Saturn and its moons

is because we've had a spacecraft there for almost ten years - Cassini.

Cassini has an amazing camera

and we have been astounded by the images it has been sending back,

forcing us to rethink our ideas about Saturn,

its rings and its moons.

It can see in different wavelengths -

useful if you want to peer through the layers of Saturn's atmosphere.

We're joined by Leigh Fletcher to tell us about stunning Saturn.

Now, Leigh, Saturn is basically a giant ball of gas, isn't it?

That's right. It's an enormous ball of gas

that's 95 times more heavy than Planet Earth.

But, in fact, because its density is so low,

it's made mostly of hydrogen and helium, if you were able

to take it and put it in a bathtub, it would float on water.

-It's the least dense planet in the solar system.

-That's right.

Here we're seeing it fantastically lit up by the sun on this side

and rings casting beautiful shadows.

Yeah, you're seeing the shadow of the rings

and one of the important things about this image is, it shows you

that Saturn normally looks rather bland

compared to something like Jupiter, that you're familiar with.

But even though it looks featureless, there are indications

-of very dynamic things happening in Saturn's atmosphere.

-Oh, absolutely.

It's a meteorologist's paradise.

We can actually study the weather system of this giant planet

and one of the beauties of having Cassini there

for almost a decade now is that we can explore

all the different seasons taking place in this giant.

So if we go to the next image, we can see a storm on Saturn.

We do get storm activity occurring.

It's maybe not quite as dramatic as something like Jupiter.

Yeah, it doesn't stand out quite as much as Jupiter's great red spot.

It does look slightly like the world's largest seagull!

But every now and then,

you get something really special happening on Saturn

and we were lucky enough with Cassini to witness such an event

over the last couple of years.

Well, let's go back to look at that.

-Let's start with December 2010, so that's this image here.

-There we go.

There's something going on,

there's a little storm, but not much going on,

and then where shall we go next? January, I guess.

-Oh, and it's broken out here.

-You can see the difference

between these two images

over just a month of time.

So the storm has popped up

and it's popped up into these winds

that are rapidly circulating around Saturn

and it's starting to be drawn up.

Let's go on to February 2011,

and you can really see what that's done to the storm,

so this storm has been stretched out.

We should say, these winds you described on Saturn,

-they're some of the solar system's fastest.

-That's right,

and this goes back to the idea that it's Saturn's own internal energy

which is powering and creating these very fast winds.

The thing that strikes me is the detail available in this image,

so let's bring the storm up and put it right across the screen

and you'll see what I mean.

We've got incredible details here,

and this is the head of the storm

and if you think that the Earth is the size of this image,

you get a sense of how big this thing really is.

What's happening in this swirling cloud structure?

Well, we had this huge plume of activity

dredging up ammonia ice and water ice,

and it deposited it at the cloud tops,

and so the winds that are taking place in the clouds

then waft all of this material downstream.

At the same time, we were detecting

super Saturnian lightning bolts within this atmosphere,

which create this incredible structure.

What is it we have happening here? Is this the head of the storm now?

This I like to think of as the heart of the storm itself.

What you're seeing here

is the birth of a large churning vortex within Saturn's cloud tops.

So these storms are absolutely fascinating,

but actually, there's some really interesting activity

happening up at the poles of Saturn, so let's have a look at those.

Right. So what do we have here?

You immediately see so much more detail.

The thing that really stands out in this image for me

is the large-scale structure, this incredible hexagonal wave.

We don't see anything like this anywhere else in the solar system.

We don't know why it's a hexagon,

and this goes back to what we were talking about with a plughole,

a swirling vortex of air

right at the north pole of Saturn.

-So what comes up at the equator goes down in the poles.

-Must come down.

Cassini captured this particular movie...

-Oh, wow.

-That's fantastic.

-..back in November of last year.

You can see this incredible, churning weather system.

That plughole you keep referring to

is right in the heart of this swirling vortex.

Now, the gas that's contained within this vortex is hot,

and you know that if you squeeze a gas together, it heats up,

and that sinking action is heating the air

within this swirling hurricane.

They're fabulous images and fantastic science,

so, Leigh, thank you very much.

And fantastic though Saturn is, it's now time to look at the rings.

The rings of Saturn never fail to look spectacular.

We can see them quite clearly,

even through a small telescope

but get up close and you see they are extremely complex,

made of hundreds of individual ringlets,

with some extending far out into space.

What's mind-blowing is that these structures are not solid.

They're made largely of tiny pieces of ice, dust and small rocks.

There are small moons running round within the rings,

called shepherd moons,

which create gaps and form these amazing structures.

But Saturn's rings still hold many mysteries.

Crucially, we still don't know

how or when the rings were formed,

but there are a couple of opposing theories.

This is a fantastic image of Saturn

showing its rings beautifully on our video wall.

Now, Saturn's being backlit, the sun is setting behind.

You can just see the sunlight coming through here,

and this is us here on the Earth,

but they look absolutely fantastic, Chris, these rings.

It's amazing to see the Earth through Saturn's rings,

but the rings themselves are exciting too

and new results from Cassini

have told us they're even more interesting than we thought.

One thing that surprised me

was that the rings are thinner than we thought.

They're just, in places, 10 to 30 metres thick,

so that's about the height of a three-storey building

and something that thin produces this spectacular structure.

One of the other mysteries about the rings is how old they are.

People have argued that because they're very bright,

they must be made of fresh water ice

or they have fresh water ice within them,

and if there's fresh ice,

that means they're young rings, no more than a few million years old.

But you could also argue that the rings are in fact very old

and they're something that formed

close in time to the formation of the planet itself.

It's one of the key things that we need to understand about Saturn.

Whether the rings are old or young, they're certainly beautiful,

but we can't talk about Saturn

without also mentioning its family of amazing moons.

The moons of Saturn are strange, wonderful and plentiful,

with the current tally running to 62,

most of them discovered within the last 15 years.

There's Mimas, the "Death Star moon"

with its large impact crater.

Then there's Iapatus, the "yin-yang moon"

and thanks to Cassini, we now know that its odd colouring

is due to dust sprayed onto it

from the tiny moon Phoebe.

Still mysterious, though,

is the ridge of ten-mile-high mountains around its equator.

Weird Hyperion looks like a big sponge

and is probably more similar to a pile of rubble than a solid moon.

And finally, there's Enceladus, perhaps the strangest world of all,

with its fountains of water spewing into space

and feeding Saturn's E ring.

The discovery of Enceladus' fountains by Cassini was remarkable

and it took some plucky flying!

Something strange had been spotted

in the magnetic field around the moon's south pole,

but to investigate this tantalising clue,

the spacecraft had to go dangerously close to the moon.

Following up on this hunch

was the responsibility of Cassini's Michele Dougherty.

What was it that first made you realise

Enceladus had something unusual going on?

The magnetic field looked different. When we looked at the data,

we could see that it was draping around Enceladus,

so it was almost as if it wasn't able to go down

onto the surface of the moon, so something was holding it off.

There was an obstacle that shouldn't have been there.

It was almost like there was an atmosphere,

so we thought we'd be brave and we went to the Cassini project.

I spoke to the guy responsible for the spacecraft

and I said, "I want to fly much closer to Enceladus than planned,"

and he said, "Oh, that's cool!"

So they changed the third fly-by to be 173 kilometres above the surface,

and fortuitously, it was going to fly below the south pole.

And that's when we realised

that there were actually cracks on the surface,

which the imaging team called tiger stripes, and out of these cracks,

water vapour was leaking, and so that was the atmosphere that we had seen.

So you've got this leaking water. Where it is coming from?

There's a liquid source underneath the surface,

a water ocean of some kind.

Why it's there we don't know, because Enceladus is small.

It should have cooled down a long time ago,

so something is keeping its interior warm, but it's not only water.

We've seen organic material as well.

Organic means chemicals, complex chemicals with carbon?

Carbon, nitrogen, methane, benzene.

All we know is that

at this little moon that we thought was a dead body,

there is a liquid reservoir under the surface.

Dust, water vapour, organic materials are leaking out.

For me, Titan is the most exiting of Saturn's moons.

In the 1980s, Voyager, in flying past,

saw an orange ball with a thick hazy atmosphere

made up of nitrogen, methane and complex hydrocarbons.

It has taken Cassini, with some help from its tiny lander Huygens,

to show us what Titan's surface is really like.

In January 2005, Huygens was released from the mother spacecraft.

This descent movie shows it plunging through the atmosphere,

being buffeted by winds which blow at up to 300 miles an hour.

On board, a microphone recorded the eerie sound of a moon,

a billion miles away from those of us listening in on Earth.

WIND RUSHES

Finally, Huygens dropped through the clouds

and was able to see the surface,

complete with cliffs, rivers and even the shore of an ancient lake.

When it landed on the surface, it cracked one of the icy pebbles,

the first example

of a prang on another world.

Since then, the Cassini spacecraft

has been using radar to map the surface.

Smooth surfaces show up dark,

so these black and blue areas seem to be liquid of some sort.

At minus 180 degrees, this can't be water.

These lakes are made of liquid methane.

Cassini can also see in infrared,

picking up the signs of clouds as well as land.

Titan, it seems, is a complex world,

just like our own.

What we've learned about Titan since Cassini arrived

has transformed our view of this fascinating moon,

and with us to discuss those new results is Annie Wellbrook.

-Welcome to the programme.

-Thank you.

What we have here is a beautiful image of Titan,

but what exactly is it showing?

This is actually showing the terrain of Titan,

so we can see the brighter areas are actually high plains of Titan,

and the darker areas are kind of the surface,

so all this different terrain, it's actually very similar to Earth.

If we go to the next image we have,

we can start to see some of these Earth-like features.

This is an incredible image. This is presumably a river.

Yes, absolutely. It's feeding into a lake on the left there.

You can see how the river is meandering

and it's just like a river on Earth, really.

But if we're talking about rain, we're talking about weather,

so does it change as the seasons change?

Yes, Cassini has now been in the Saturn system for almost ten years.

We can now start to observe seasonal changes

and that's such an exciting thing to do

because we're realising that, actually,

the seasonal changes are again similar to Earth's seasonal changes.

Where does all this methane come from on Titan? What's the source?

It has been kind of a mystery for a while

because there's all this methane in the atmosphere

and it gets broken apart by sunlight. For a long time,

scientists have thought that

there must be a source replenishing the methane,

but actually, there was a recent paper where they talk about

maybe the methane isn't being replenished,

and Titan is going to run out of methane

in tens of millions of years.

That seems really quick.

Yeah, in planetary terms that is not a very long time.

But I really didn't know about this! And I'm really disappointed.

This is actually really upsetting,

because I wanted Titan to be a place with methane, with oceans,

with lakes, with places where life might have even got started.

People thought of it as a laboratory for the early Earth,

and now you're telling me that might just be

the last few tens of millions of years.

Maybe. At the moment it is a theory,

and there's still plenty of methane around.

In your lifetime, it's not going to run out!

-So don't worry about that.

-That's good to know.

Whether we're down on the surface or up at the top of the atmosphere,

there's no doubt this is a fascinating world,

so thank you so much for coming to tell us about it.

Thank you very much.

When you think that all we used to know of Titan

was that it was an orange ball,

it's now amazing to think what might be going on beneath these clouds.

Our exploration of Saturn has come to an end

and we're coming back down to Earth

to find out about a camera that's being built right here.

At the Rutherford Appleton Laboratory

they are getting two very special cameras ready for space,

and a journey to the International Space Station.

Looking at Earth is a magical experience.

You never get tired of an astronaut's view of our home planet.

There are no space cameras available to the public

which can see the Earth's surface in detail, until now.

When fitted, we will be able

to look at the Earth's surface,

making out metre-sized objects,

for the very first time.

'Called Urthecast, it's a Canadian venture

'with Russian and British partners,

'and Tom Morse is the electronic design engineer

'who's working on the project.'

Right, so we're here at the entrance to the clean rooms,

where the cameras are being assembled. In order to go in there,

we need to get all kitted up in the clean room gear

to make sure we don't do anything that will contaminate the cameras.

I feel like I'm being some sort of dinner lady!

-Right, a face mask here.

-Thanks.

-So if you hold on to that bit.

Just pull it over your head.

Ah-ha, here we have it.

So here we have the high-resolution Urthecast camera.

This is going to be mounted on a steerable platform

on the Russian segment of the International Space Station.

It's going to be taking video at 3.25 frames a second

looking down onto Earth and beaming those pictures down to Earth,

so anybody can access those at home.

What size of features will this telescope be able to pick out?

It'll be able to pick out features about 1.1 metres on the ground,

so you'll be able to see houses,

you'll be able to see sporting stadiums, you'll be able to see

natural disasters taking place on the Earth from space.

What about the other camera? What will that be doing?

As well as the high-resolution camera,

we've got what we call the medium-resolution camera,

and that camera will be pointing

directly down from the space station,

scanning across the Earth at 17,000 miles per hour

and building up strip images of the ground as it passes over.

And as the Earth rotates underneath that orbit

it's going to build up a picture of the entire Earth.

And how frequently will this camera

be able to build up a complete snapshot of the Earth?

We're looking at revisiting each spot on the Earth

about roughly every month, something like that.

This is a totally new kind of project, isn't it?

We haven't had these kind of images publicly available before?

Exactly, so the point of Urthecast is to give everybody on Earth

the perspective that you can get from the space station.

People in their armchairs at home are going to be able to log in

with their laptops or their phones and they'll be able to see

what an astronaut's-eye view is like from space.

The cameras go up to the International Space Station in October,

and I know I'll be giving it a try.

It's back now to stunning Saturn

to join Pete and Paul in Hampshire,

who hope to see it in the night sky.

'Pete and I have come to Clanfield

'to visit the Hampshire Astronomical Group,

'who affectionately call themselves HAGs!'

The group have a variety of telescopes.

This one is 117 years old.

'Graham Bryant helps keep it in fine working order.'

Hello!

Oh, wow, look at that. A proper telescope. It's very impressive.

-This is a refractor.

-It is.

-What size is this?

We've got a five-inch Cook refractor

-and a four-and-a-half-inch Smith, Beck, and Beck.

-Wow.

What sort of focal length are you talking about?

The Cook is an F17 so it's brilliant for planetary and lunar work.

And what about this? This looks like the original drive.

-It is, yes. This is an old weight drive.

-Wow.

I tell the visitors that this was driven by gravity.

-Is it easy to manoeuvre?

-Yes.

-Let's have a little...

-Oh, that's very smooth motion.

-Yes.

See, this is much better than yours, Pete. A proper telescope!

It's very impressive. What sort of things do you concentrate on here?

This is used mainly for planetary work, lunar work and solar work.

Well, it's clearing up nicely up there, so I wouldn't mind

-having a look at Saturn through this later.

-That would be good.

The sun is setting

and it's time to brave the elements and set up the telescopes.

A small group of astronomers have joined us,

some of whom are new to the wonderful world of Saturn.

Can you see to that one, or does it need to come lower again?

A bit lower, please.

Paul and Olivia live nearby.

-What have you got in the telescope?

-Currently, we're looking at Jupiter.

-Can I have a look?

-Certainly can.

-Let's have a look. What have we got?

That's a lovely image.

-I see one of the satellites is transiting.

-Satellites?

A satellite is a moon and Jupiter has four really big ones,

Io, Europa, Ganymede and Callisto,

and if you have a look through the telescope, what can you see?

There are two moons to the right of Jupiter,

but because this is reversed

and it's back-to-front,

it looks like it's at the bottom, but it's at the top.

Pete Lawrence, the fountain of all knowledge and wisdom,

has just informed me it's Callisto,

so that's one of the moons passing over.

-Quite pretty, isn't it?

-Yeah.

Hopefully, later on, Saturn will be rising over there in the east,

so we can have a look at it,

and your telescope should bring out some nice details, I think.

For Christina, Saturn is one planet

she has been looking forward to getting in her viewfinder.

-Christina!

-Hello!

-Hello again, hi.

What are you looking at? The moon?

I'm looking at the moon, yes, big and bright.

It's actually first quarter at the moment,

so that shadow line is right the way down the middle of the moon.

-Have you had a chance to get out and see Saturn?

-I have.

-You have?

-I've seen it for the first time.

-Wow. What was your reaction?

-Wow!

-Yeah, it is, isn't it?

I mean, it was teeny tiny, but still wow.

Becky is new to astronomy and really enjoying it.

-Becky, welcome to The Sky At Night.

-Thank you.

-You're an absolute beginner, aren't you?

-Total absolute beginner, yeah.

What sort of things have you been looking at?

I've been looking at Jupiter as that's the easiest to find in the sky

and I remember seeing Jupiter for the first time through it

and it was like, "Wow, that's absolutely amazing."

Have you had any luck with anything else?

I'm hoping to see Saturn tonight, that's kind of on my tick list today.

-Fingers crossed for clear skies!

-Thank you very much.

-Let's hope for the best.

-Thank you.

With a small telescope,

you can see Saturn and its rings and some of the moons,

but with a bigger one, you can see much more detail

such as the subtle banding on the planet.

Its rings have features too -

the outer A ring, then a gap

called the Cassini Division,

and then the inner B ring.

Yeah, I thought it would be a bit of a blur,

but you can actually see everything.

-Yeah.

-You can see the rings and...

-Yeah. Yes.

Tonight, with Saturn so low down,

it's going to be tough to see that detail.

Ah, Olivia, you're looking through the telescope.

That's what I like to see. What are you looking at?

I'm looking at a picture of Saturn.

So what do you think of it as a planet?

It's quite nice with the rings.

-You can see the divisions, and you can see the moons.

-Yeah?

When you're looking at the rings, so you've got the planet in the middle

and you've got the rings that go around them, so you can see the gap

-between the rings and the planet, you can see that?

-Yeah.

Can you see in the rings that there is a sort of dark line

running around between the rings,

sort of dividing them up?

-It's not easy to see.

-Sort of.

-Sort of?

Keep a look out for it, and it will get better.

So, we're with Becky

-and you've done something brand-new tonight, haven't you?

-Yes, I have.

-Go on, tell them. Tell them!

-It's totally amazing.

-I have actually found Saturn through my telescope.

-Hurray!

-Well done!

-Brilliant!

You've got your little three-inch telescope here.

It's obviously Saturn, isn't it?

With the rings and the satellite, so you must be very proud.

Yeah, I'm really proud. It took me a while, but I'm so excited

that I found it. It's absolutely brilliant.

You have to be patient when looking at the planets,

especially Saturn with its gentle pastel colouring.

Keep looking through the eyepiece and that detail should emerge.

-Come and have a look at this.

-OK.

Your perseverance will pay off.

Oh, yeah. You can start to see the shadows on the globe now.

If you'd like to find Saturn in May's night sky, go to our website.

Pete has some helpful star charts.

There are some nice globular clusters such as M13.

You'll find charts for those too.

Yeah. That's amazing.

-Beautiful, isn't it?

-Wonderful.

We have one more chance to see Saturn with the old telescope.

-Hello there.

-We thought we'd come back for a final view of Saturn

through this magnificent antique piece of yours.

Well, it's a very nice, steady view at the moment.

-Do you want to take a look, Pete?

-I'd love to have a look.

-Go on, you go first.

-This is 117 years old, this telescope.

-Yes.

-That's incredible.

It looks so beautiful, doesn't it, in this light?

-Oh, that's just gorgeous.

-Is it a good view?

It's absolutely beautiful. That's the classic view

that looks as if someone's cut out a picture of Saturn

-and stuck it on the front of the telescope.

-Absolutely.

-Let's have a look.

-It's lovely, absolutely beautiful.

And where's the focusing?

Ah, there it is. So let's have a look. What have we got?

Oh, my word, look at that.

That is a magnificent view. I have to say,

I think this is better than the view in your 24-inch.

The magic is always there.

Spectacular Saturn, out amongst the stars of Virgo.

Well, thanks, Graham,

for showing us Saturn in this beautiful constructed telescope.

I think it's been one the best views of Saturn for a long time.

-Thank you very much, Graham. That was brilliant.

-You're both welcome.

Well, weren't Pete and Paul lucky to get such good weather?

Let's hope we have clear skies this month too.

The Sky At Night's Space Surgery

has been receiving lots and lots of your queries,

and on call this month, as ever, Chris North.

-Chris, what have you got for us?

-We've had a lot of questions

and our first one this month refers to the planet Saturn,

that we've talked about for most of the programme.

Coming in from James Coyle, aged five, from Northern Ireland,

who asks...

James, although Saturn is the planet that's by far the most famous

for its beautiful ring system,

the other planets, Jupiter, Uranus and Neptune, the large planets,

do in fact have ring systems.

They're very hard to detect, they're very faint,

and they've only been discovered in the last few decades.

Chris, our next question is for you. It refers to last month's programme.

It comes in from Kevin Geary, and many others,

who've asked about that rock you were holding

that you claimed was from Mars.

People should just believe me.

I think that's the easy way, but actually, the reason we know

this particular rock was from Mars is, we have sort of been there.

We've sent probes there,

and in particular, the Viking probes in the '70s

told us about the chemical composition of the Martian rocks

and, in fact, the atmosphere.

So when we find that composition in a meteorite that's landed on Earth,

we are able to say yes, this definitely isn't Earthly,

this rock comes from Mars.

And they're precious because these are the only samples we get back,

so until we go to Mars and pick some up, we need these meteorites,

but we can be sure they're from Mars.

And, Lucie, finally, last one is for you.

It refers to the gas giants again,

so Jupiter and also Saturn have atmospheres

of mainly hydrogen and helium.

Audrey Michie from Turriff asks...

So as the meteor comes in,

it does indeed burn up as it goes through the atmosphere,

but even though hydrogen is very explosive, for example,

if I had a balloon full of hydrogen and I put a flame to it,

it would explode and make a huge bang.

We also use hydrogen to get rockets into space because we burn it,

and there is no oxygen in these planets

to allow the hydrogen to burn, so that's why it doesn't set light.

Lucky for the planets, I guess,

otherwise it would be a very big fireball!

Keep your questions about this programme

or in fact anything to do with astronomy coming in.

You can do that at our website...

We look forward to the challenges you'll set us.

Yes, do try to catch Chris out. But when we come back next month,

we'll be talking about the lives of the stars. So until then...

ALL: Good night.

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