Jupiter: Weather and Moons The Sky at Night

THEME MUSIC: "At The Castle Gate" from "Pelleas and Melisande Suite" by Jean Sibelius.

Welcome to the Royal Observatory Greenwich,

the historical home of British astronomy

and a place with a surprising link to this month's topic.

The big story at the moment in our night skies,

is the fifth planet of the solar system, the mighty Jupiter.

And that's what we're going to explore in this programme.

Coming up, physicist Helen Czerski will be trying to uncover

some of the mysteries of Jupiter's atmosphere.

The memorable thing about the Great Red Spot

is it's been there for so long.

These features will persist for as long as the experiment runs.

Pete Lawrence will be showing us

just how easy it is for anyone to get a great view of Jupiter.

We'll be finding out about an astonishing new discovery,

water spraying out from one of Jupiter's moons.

We're talking about a plume of water 200km high

over the south pole of Europa.

And how the pictures you take

could be an essential tool in the study of the gas giant.

Jupiter is always a wonderful object to see in the night sky

but right now it's truly spectacular, outshining

even the brightest stars.

For the next few months, it'll be high in the sky after sunset

making this the best opportunity for British observers to get

a look at this fascinating world.

One of the joys of observing Jupiter is seeing those distinctive bands

and, of course, the Red Spot.

This image shows that in amazing detail.

Now the bands are actually formed by

a weather system which goes all

the way round Jupiter, with wind speeds greater than 300mph.

The Great Red Spot is actually three times the size of planet Earth

and has been raging for over three centuries.

And it's to this amazing weather that we turn first.

We sent physicist Helen Czerski

to see she could find out what causes this magnificent display.

When you look at an image of Jupiter, the most obvious thing are these

fabulous bands of colour that go horizontally across the surface.

But Jupiter doesn't really have a surface as such

because it's a gas giant.

What you see on Jupiter are swirling clouds of many different gases,

effectively what we're looking at

are just the tops of complex weather patterns.

But what drives this violent and long-lasting weather?

You'd think that - you can see so much detail -

the answer must be obvious but actually this is

one of the biggest mysteries in the Solar System.

One of the clearest features we can see from Earth is that

the atmosphere is arranged in a series of bands circling the planet.

These bands are iconic,

really strongly associated with Jupiter,

but this isn't the only planet to have weather in bands like this.

Saturn has clearly defined stripes of light and shade.

Neptune also has subtle visible bands.

The bands of weather that we are most familiar with

are actually here on Earth, it's just that we can't see them

because our atmosphere is transparent.

But they are there.

Earth's atmosphere is actually divided into distinct regions

known as cells.

Each cell is driven by hot air rising high into the atmosphere

and flowing either north or south.

There are six in total.

And the thing that I like about the comparison between Earth

and Jupiter is that we can't see those bands, those cells,

on Earth, but on Jupiter they are really visible.

Jupiter has many more cells than we have on Earth, there are at least 12.

And that's not just because it's bigger, the number of cells

a planet has actually depends on how quickly it's rotating.

Earth rotates once every 24 hours, that's what defines a day.

But Jupiter rotates roughly once every 10 hours, over twice as fast,

and if Earth did the same, our weather would be very different.

This is a simulation of the Earth as it is now,

looking slightly down from the northern hemisphere.

So the planet is rotating this way around.

What the colours represent are wind speeds high up in the atmosphere.

But if we change the simulation, so we speed up the rotation speed of the

Earth by a factor of four, a six-hour day, this is what it looks like.

You can see that suddenly there are many more bands

stretching around the planet.

The winds are constantly being pulled in a lateral direction, and that

means it's really hard for currents from the north and the south to form.

So the structure of Jupiter's atmosphere

is locked in these bands that we're all so familiar with.

The bands of fast-moving winds aren't the only

weather we can see on Jupiter,

there are also extraordinary vortices and spots,

some of which last for centuries.

But why did these atmospheric storms last so long?

I'm meeting Professor Peter Read, who is using a jug of water,

some sparkling dye

and a rotating rig to recreate a section of Jupiter's atmosphere.

Jupiter is quite unlike the Earth in many respects.

And in one important respect,

and that is that on the Earth, the equator is usually hot

and the poles are cold,

on Jupiter that's not the case.

What we tend to see is that the main temperature differences that we can

measure in the atmosphere are actually between the bright bands

and the dark bands. You will typically have

a bright band, which is relatively warm,

and then, to the north and the south of that,

there will be a dark band that is relatively cold.

That sounds amazing to me because I'm used to thinking about the Earth,

and the idea that the equator is hotter and the poles are cooler

is such a strong idea and that drives

all of our weather on this planet, but Jupiter is quite different.

And Jupiter has an extra ingredient that the Earth doesn't have and that

is that Jupiter itself is a source of energy from its deep interior.

It actually generates almost as much energy from

its deep interior as it receives on average from the sun.

With this experiment, we're trying to create a simulation of

what happens within one of Jupiter's bands.

The water is heated but the edges

in the centre of the vessel are cooled,

this represents a warm band on Jupiter surrounded by

colder air, and then the whole experimented is rotated.

After a few minutes, some vortices are created that are

so stable they barely appear to move.

So what you can see in now is a whole chain of these eddies

that are circulating in the same sense.

So if this was a band on Jupiter,

at the bottom of the band the winds are going this way round

and then you've got these eddies spinning like this,

-but at the top, the winds are going the other way.

-That's right.

So this is just like the bright bands on Jupiter.

So in the south, the jets will be going in one direction,

and to the north, they'll be going in the opposite direction

with these vortices rolling in between them.

These rotating storms are trapped within the bands that have been

created by Jupiter's fast rotation.

This means they are remarkably stable.

On Earth, storms come and go, but on Jupiter

the really memorable thing about Great Red Spot

is it's been there for so long.

These little storms you've generated

in this experiment are just persisting.

These features will persist

for as long as we keep the experiment running,

once the whole thing has settled down.

This is just a two-dimensional representation

of what might be happening on Jupiter,

but our knowledge doesn't go much beyond that.

The problem is that when we look at the planet,

all we can see are the tops of the clouds

and it's really difficult to measure what's underneath that.

Finding out what's happening deep within the planet

is the next great challenge.

Luckily, there's hope that we all resolve some of these

unanswered questions in the near future

because NASA's Juno probe is on its way to Jupiter.

It's spent the last couple of years wandering around the inner

Solar System picking up speed, and at the end of last year, it

passed by Earth for its final gravity assist.

Remarkably, amateur astronomers were able to image it as it flew past.

In this sequence of images from Peter Birtwhistle,

the moving dot you can see is Juno itself

heading off to Jupiter.

Juno's on-board instrumentation will allow us

to peer below the clouds for the first time.

It will fly very close to the planet,

a mere 5,000km above the clouds

and below the radiation belt,

which has stopped us from taking detailed data in the past.

It will take detailed gravitational measurements

and measure the atmospheric composition,

it will also measure the mass of Jupiter's core, if there is one.

It's an incredibly exciting mission but we'll have to wait

until 2016 for Juno to arrive.

Now you don't need to travel to Jupiter

to get a fantastic image of it.

It's possible to capture really

detailed pictures of the planet from right here on Earth.

And images like these, taken by amateurs,

actually provide a unique record that even the space probes can't match.

I've been speaking with Professor John Rogers,

who gathers these images into a database

that scientists can use.

How are amateurs helping us understand Jupiter,

where professionals can't?

Well, amateurs are able to monitor Jupiter continuously,

and its weather systems evolve over timescales from days,

to months, to years, to decades,

so we really need continuous observations

to work out what's happening.

They're not just doing observations, they're doing some science too?

Yes, well, we can actually compile a record of what's going on,

how spots like the Great Red Spot evolved,

and we are able to monitor much smaller spots as well.

Here for instance, you see the Great Red Spot, you can

also see that the belts are not symmetrical.

This dark belt is here but there's normally a dark belt up here,

which, on this occasion in 2010, has disappeared.

So these kind of changes are happening all the time on Jupiter,

sometimes they take many years to unfold,

and that's what amateurs can really study.

I'm not used to seeing Jupiter in this orientation.

This is the way that amateurs most commonly see it, with south up.

So the Great Red Spot is in the southern atmosphere

and that's how we put all our pictures up for display.

But it's not just weather that the amateurs are spotting,

they also find impacts.

In 1994, the comet Shoemaker-Levy 9

crashed into Jupiter,

leaving dark scars in its atmosphere.

Since then, amateurs have discovered that these

kinds of impacts are more common than previously thought.

In 2009, quite unexpectedly, an amateur, Anthony Wesley,

discovered such a spot on the planet.

This was an image he took two nights earlier,

and then he saw this remarkably black spot

appearing and realised that this might well be an impact.

So other amateurs immediately started taking images to confirm

and professional scientists took this image

in a far-infrared wavelength.

The Hubble Space Telescope took this image a few days lays later.

The professional astronomers managed to follow this event

over several months,

while the amateurs were also tracking over several months.

The amateurs are the watchkeepers, they keep on eye on Jupiter

and alert the professionals when something exciting happens?

Yes, indeed.

More recently, amateurs have been noticing impacts while they happen.

They are much smaller impacts, they don't leave visible scars

but they're more frequent. And so three times since 2009,

amateurs have actually seen fireballs in the atmosphere

of Jupiter, which previously, if anyone had seen them,

they didn't notice them or didn't believe they were seeing them.

But now we have real webcam videos and it's clear that

amateurs are actually detecting flashes as they occur.

So how does an amateur get involved?

The best way for someone who hasn't done it before is to

contact their local astronomical society.

There they'll meet people who are themselves

getting into the same kind of observations,

finding out how to use the same kind of equipment,

and I think that it's the personal contacts

that are most useful to someone

who hasn't experienced this kind of technology before.

Thanks, John, that was pretty fascinating

-and it shows the power of amateur astronomy.

-Thank you.

Now Pete Lawrence is here with his guide to what else you can

see in the night sky around Jupiter.

But first, he's got a simple tip that can help address

one of the main problems that people face when they're stargazing -

how to match a star chart to the real night sky.

And he's with the Hampshire Astronomical Group on the South Downs.

Jupiter is pretty easy to find at the moment

because it's the brightest thing visible in the early evening

part of the night sky, apart from when the moon's about, of course.

For many people, when they look up at the night sky,

it can be a bit of a challenge to work out what is what.

But there are a few simple tips you can follow which will

make your life easier.

One of most difficult things for those starting out

is judging scale.

How do you relate the distance between stars on a star chart

to the distance in the night sky?

It might sound surprising,

but the best thing to do is to use your hands.

If you hold it out at arm's length,

like that, the distance between your thumb

and little finger is the same.

If you've got big hands or little hands,

the length of your arm tends to compensate for it.

So if you look at Orion - you can

see the bright star in the upper left corner

and the bright star in the lower right corner - you can

see that it fits more or less between those two.

For all of us, even though

we've got different sized hands and different length of arms,

you can actually hold two fingers up as well, that's a good indicator.

Just starting to appreciate the scale of patterns in the night sky

and you can relate that back to a star chart

and then gradually work your way across the sky.

Once you understand the apparent distances between stars,

finding anything in the sky should be much easier.

Jupiter is obviously the highlight up there at the moment,

it's magnificent.

But there's a lot more to be seen around that area and I've picked out

some of my favourite highlights for this month's star guide.

The magnificent constellation of Orion lies south in the early

evening during February.

Its seven bright stars are easy to pick out

and create a great signpost in the night sky.

Look out in particular for Orion's Sword that appears to hang

down from the belt, a region which contains the fabulous Orion Nebula.

Follow the line made by

Orion's Belt down the left

to locate Sirius -

the brightest night-time star.

About one-and-a-half

outstretched hand widths

above and left of Sirius is another

bright star called Procyon.

Join the dots of Sirius, Procyon

and orange Betelgeuse to form

a pattern known as

the Winter Triangle.

The winter Milky Way

passes through this region.

Scanning the area

with a pair of binoculars

reveals many faint

and beautiful star clusters.

Extend a line from Rigel, in Orion,

through Betelgeuse for twice the distance again -

that's two outstretched hand widths -

to arrive at a pair of stars

in Gemini known as Castor and Pollux.

They are about three finger widths apart.

If you traced the pattern of the famous twins back towards Orion,

you'll find the unmistakably bright planet Jupiter.

Jupiter is currently visible more or less all night long.

If you go out and catch it early, it's possible to see

a full rotation of the planet, that's one whole day on Jupiter.

If you get some lovely pictures of that, send them in to us

and we'll put the best ones up on our website.

Speaking of your photos, we've got

some great ones that have been uploaded to our website.

And here are a few that really stand out.

This is the Orion Nebula, which lies on Orion's Sword,

taken by Steve Richards.

Luke Stacy captured this image

of a chain of sun spots on 2nd February.

This shot by Mary Spicer shows how light bouncing off

the Earth can illuminate the parts of the moon that lie in shadow.

And this is Centaurus A,

a galaxy that lies too far south to be viewed directly from Britain.

It was taken over an astonishing 43 nights by Rolf Olson.

To send us your images, go to our website at...

Since we were last on air,

there has been plenty happening in the astronomical world

-and the most spectacular event has been a new supernova.

-Yes.

A supernova is the dying throes of larger stars.

And we have one here captured by some UCL students.

So this is the M82 cigar galaxy.

And here, on 21st January, we have a new bright object - the supernova.

And what I love about this is this discovery was made by Steve Fossey

and a bunch of students just up the road

at the UCL's Mill Hill observatory.

But even better, it was a ten-minute gap where it wasn't cloudy.

-Exactly. A discovery from within the M25.

-And it's perfect.

-It's a type 1a supernova, which are quite rare.

-That's right.

We use these to measure how the universe is expanding.

So they're bright, so you can see them from a long distance away,

and that means we can use them

to work out how the universe is accelerating.

But, embarrassingly, we don't know what they are.

We've ideas that they might be a massive star spiralling

material down onto a white dwarf, which then explodes, but we're

not sure and that's why we need these local ones to try and help us.

This is 12 million light years away

-which is pretty local.

-Just round the corner.

Yes! Is still visible now or does it decay very rapidly?

It will be visible for the next few months.

It was caught early enough that it was still brightening

so it will be at its brightest about now.

So go out, find M82.

If you look in binoculars, you should see it easily.

It won't quite make it to naked eye visibility

unless something odd happens

but it'll be an easy target for binoculars.

The brightest supernova

we've had in the northern hemisphere for years.

Speaking of celestial spectaculars, we had hoped before

Christmas that comet ISON was going to put on a great show for us

but it didn't quite work out like that

and Alan Fitzsimmons is going to tell us why.

People were predicting that ISON would be the comet of the century

that, as it came round the sun,

a huge tail would be created that would fill the night sky.

However, instead, it seems to have fizzled out.

But now, by pulling data from a number of scientific instruments,

it's possible to find out what actually happened.

Here we've got the comet

about a couple of hours before closest approach to the sun.

We can already see that something has happened to the comet.

In a normal comet, we expect to see

a very bright, distinct head, or coma,

form from all the gas

and small dust particles that the comet has released.

Here we can see the tail of the comet

but the head itself is already

not looking like a normal comet does -

it's spread out.

And even by this point,

a couple of hours before it reached

its closest point to the sun,

the comet nucleus itself

had been dispersed. Interestingly,

it's still far enough from the sun that it shouldn't have been

broken up by the gravitational field,

the tidal forces imparted on the nucleus by the sun,

but what's happened is simply its nucleus has been heated

so much and is releasing so much gas and material from its surface,

that pressure of that material building up in the comet

has simply broken it apart.

And so ISON was doomed long before it reached the sun.

And as it passed around our star,

it reappeared as nothing more than a cloud of debris.

But there is still a question about

whether anything of the nucleus had survived to live another day.

On December 16th, the Hubble Space Telescope went to have

a look at where the comet was predicted to be.

Now it's tracking where we expect the comet to be moving,

so all the background stars and galaxies appear as streaks.

But if there was any comet left, we would see it as a point-like

source here and we don't see anything.

So these Hubble Telescope images here

imply that there really isn't anything left at all of the nucleus.

So it's a shame. ISON is gone -

but it gave us a great show on its way in.

And we've got one more item of news this month.

In January, as part of Stargazing LIVE,

I challenged people to go online and look at pictures of galaxies

and look for gravitational lenses -

places where a distant galaxy has had its light bent

by a gravitational lens, by passing near a nearby galaxy.

We found lots of spectacular things

but the one we talked about on the night was this one.

-This is an infrared image of that galaxy.

-Yes. What have we got?

-In the centre, that's the galaxy?

-That's the nearby galaxy.

And the red arc that you can see, almost the red ring there,

is a distant galaxy whose light has been bent

and we're seeing it because it's being lensed by this nearby galaxy.

Without that galaxy, we wouldn't have a chance of seeing it?

Exactly. It's nature's telescope.

This is the infrared. What we've been doing since

is we've looked at it in the radio using Jodrell.

-This is the image that we've got.

-It does look like different.

It does.

For starters, it's blobby because it's a radio image

and you don't get the beautiful pictures you do in the infrared.

The other thing, I don't know if I can convince you of this,

but in the infrared we saw that red ring,

in the radio, it's only one arc.

It definitely looks one-sided.

-So where's the rest of it gone?

-Exactly. It's quite confusing.

Our best guess at the minute is that the radio

and the infrared radiation come from different parts of the galaxy.

So the infrared comes from star formation spread out through

the whole galaxy - and the galaxy's forming stars at a great rate,

about 100 times that of the Milky Way.

And the radio, we think, comes from right in the centre,

from the nucleus where material is spiralling onto

what must be a growing black hole in the centre of this galaxy.

This is what I love. Looking at the sky

in different bands of the electromagnetic spectrum

gives you a very different viewpoint and different understandings.

That's right. We knew that was true.

It's only the second time that we've seen this

misalignment between a radio lens and an infrared lens.

A perfect ring in the infrared and nice to blobby arc in the radio.

It's quite fun.

If you go to the Sky At Night website,

we've actually put some more data online. If you follow the link,

you might be able to discover your own lensed galaxy.

Well, back to Jupiter, and we're in the Endeavour Room

of the Royal Observatory Greenwich,

which these days is a library but which used to house

some of the largest telescopes on the site.

It was in this room, in 1908, that British astronomer

Melotte discovered a moon of Jupiter.

This is the image and this dot here is the moon we now call Pasiphae.

Exciting things are happening with the moons of Jupiter

and to discuss them I'm joined by Dr Leigh Fletcher,

an expert on the Jupiter system.

-Leigh, welcome to the programme.

-Thank you.

We're going to talk about Europa,

where jets of water have been discovered shooting into space.

We knew there was water on Europa already.

We did. Europa has always been a tantalising place for us

to one day go and explore and now more so with this new result of

plumes of water vapour being emitted from the south pole of Europa.

It's going to be a fabulous thing for us to go and look at one day.

Europa's an icy moon and that's what we see when we look at the surface.

Europa is the second of four Galilean satellites in orbit

around the Jupiter. It's about the size of our own moon.

If you look at it here on the screen, you can see.

It's an icy ball, Europa is,

and the different colours that you see across the surface

are contaminants in the ice itself.

It almost looks like you've got a frozen ice raft,

frozen then into a body of liquid water that has re-frozen.

We call it chaos terrain.

-We can zoom in to get a proper look.

-Yeah.

-There we go.

This is one of the key pieces of evidence which suggests

that beneath this terrain there is liquid water.

Liquid water in our solar system locked away beneath the icy service.

We've been talking about this for years. There's an annoying catch,

isn't there, that the ice is pretty thick?

This is the typical thing within our solar system of the ability

to sense what we really want to see, which is that ocean,

is forbidden to us because it's hidden away,

locked away, or so we thought.

But now, with the discovery of these water vapour plumes,

we have a tantalising chance to fly through those plumes

-and sniff out the composition.

-Let's look at that that new observation.

This was released at the end of last year.

It's a Hubble Space Telescope observation.

And I have to say, Leigh, looking at this,

it's not hugely convincing.

I'm very sorry that you're disappointed but this is actually

a really exciting discovery that the folks with

the Hubble Space Telescope made just that while ago.

Don't forget that you're seeing this from planet Earth,

five astronomical units away.

Five times as far away from the sun as the Earth is.

Absolutely. All the way out at the orbit of Jupiter.

This is an artist's impression superimposing the two together.

What they're looking at here is

ultraviolet emission from hydrogen and oxygen.

So this is water that has been spewed out of the moon

-and has then been disassociated, split apart...

-By the sun's light.

Exactly, by UV radiation.

We can see that emanating from the south pole.

We're talking about a plume of water 200km high

over the south pole of Europa.

I can tell you we didn't expect to see that.

How have we got water at the south pole?

What's going on here is we've got these cracks, and these fissures

and stripes, which are undergoing different amounts of stress

as the moon goes round Jupiter.

The orbit of Europa around Jupiter is not perfectly circular

and that means sometimes it's closer to Jupiter,

where the gravity's stronger,

and sometimes it's further away, where the gravity is weaker.

Jupiter's a big thing, its pull is pretty significant.

It's an immense gravitational field,

that means, when Europa is far away from the moon...

Like this observation.

Like this observation in December 2012, things are relaxed,

you're able to emanate these plumes out of the south pole.

Now the team also have observations from just a month earlier.

At that point, Europa was much closer in to Jupiter,

so where the gravity field is stronger,

if you like, no plumes were observed at that point.

So you have this situation, extremely dynamically rich,

where the plumes are only emanating their material into space

when the stress is at its lowest point -

at the furthest distance away from Jupiter.

Now this is a fabulously exciting discovery.

It provides access to this water -

the stuff we thought was locked up under the surface -

and you have a mission, or you're part of a team

working on a mission, called JUICE, which is heading to Europa.

How does this change your plans?

It's being built by the European Space Agency to launch in 2022,

or thereabouts and, at the moment,

we are scheduled to have two flybys of Europa in 2031.

We are going to be up close and personal with those plumes, able to

look at the light as it is being filtered and scattered through them.

We've even got instruments on-board capable of detecting

the sorts of materials that are emanating.

There's a huge caveat to that, I should say.

What if this material isn't coming from the ocean?

Maybe it's the action of something heating up

in just the very top layers.

Even then, it's still exciting because it's a way

we can sample the surface materials

from our spacecraft without landing on the surface.

So when does JUICE get there?

JUICE will get there in 2030 and it will fly by Europa twice in 2031.

-Fabulous. Come back and tell us about it and good luck.

-Thank you.

-Leigh, thanks a lot.

-Thank you.

So that's it for this month, but do remember to keep on sending

your pictures in, especially if you manage to get

a full rotation of Jupiter, and we'll put the best on our website.

When we come back next month, will be listening to the cosmos -

studying sound waves to find out what they can tell us

about the Universe's hidden secrets.

And we'll also be looking at how to get

wonderful images of the night sky with just a smartphone.

-So remember, get outside and get looking up.

-Good night.

THEME MUSIC: "At The Castle Gate" from "Pelleas and Melisande Suite" by Jean Sibelius