Other Solar Systems The Sky at Night

Good evening.

You know, our solar system is one of many.

One star - the sun, the planets - Venus, Mars, Jupiter and the rest,

and, of course, our own Earth.

Are there other solar systems? Surely the answer is yes.

With me are two experts - Dr Chris Lintott

-and Dr Lewis Dartnell.

-Evening, Patrick.

First of all, what do we think about finding other solar systems?

Well, the first thing I think, Patrick, is it's incredibly difficult

and for hundreds of years people have speculated

that there might be planets around other stars

but we haven't had the tools we've needed

or the techniques we've needed to go after them, until recently.

The key, it turns out, is to look very closely at the stars themselves.

The first method that was used to discover planets

is called the wobble method, the radio velocity method.

I think I'm going to demonstrate this by picking up the sun over here -

which we can only do on this scale.

Actually this isn't the sun, this is a distant star.

We've got a big, juicy, gaseous planet there.

What I want you to imagine is that this planet is orbiting the star.

What's happening is that the star's gravity is pulling on the planet

but the planet's gravity is pulling on the star.

And so the star is drawn towards the planet so we get the slow wobble

back and forth as the planet moves. Now, it's not a very big wobble.

In our solar system, more than 99% of the mass is the sun.

But it does wobble nonetheless at about walking speed,

a few metres per second.

By looking very carefully at the light we get from the star,

we don't see the planet but we do see this wobble.

Then we can detect that there's a planet there

and, Lewis, we can find out something about the planet itself.

Well, we can because we work out, roughly,

what the mass of the star is

from the colour and how bright it is and characteristics...

-We understand stars.

-Well, we've been looking at them for thousands of years.

Using this method, and we first discovered a planet orbiting at a main sequence

a normal star back in 1995

and so today we are very much in the golden age of discovering new worlds orbiting other suns in our galaxy.

It's like being back in the 1500s and discovering new continents.

We're discovering new worlds now.

Have we any idea what these planets have been like?

The very first planets we discovered were the easy ones to spot -

they were the fat, gassy planets like Jupiter

and they tend to be orbiting very closely to the star,

because they had the greatest effect on the tugging back and forth.

So the closer they are, the bigger the wobble, and so the first planets we found were these hot Jupiters -

these very big planets often bigger than Jupiter,

very, very close to their parent stars,

orbiting in just a few days in many cases.

-They must be weird worlds, don't you think?

-Weird indeed.

I am prepared to believe that somewhere in the universe

there may be an intelligent astronomer

who looks like a cabbage and squeaks like a mouse.

-I can't actually prove it.

-You'll need to find the right world.

I was going to say, I thought you were describing

some of our colleagues there, Patrick!

We have started to read the chemistry

-of some of these extra-solar planets, the atmospheres.

-Oh, yes.

People have spotted the signature, the fingerprint, in the spectrum

and the colour of the light from the planet.

They've detected water vapour and carbon dioxide and methane.

So the beginnings of chemistry and characterising these planets.

Those are the three things needed for life.

What about Jupiter's moons? If you put one of these hot Jupiters

and it has moons just like Jupiter and Saturn do,

maybe they're worlds where life can exist.

Exactly. You need the right kind of world to host life.

Perhaps a rocky world like Earth

or maybe an icy world with a molten water ocean beneath it,

somewhere like Europa.

But it's not just the kind of world you need

but the location of that world in its solar system.

So, we can perhaps demonstrate this. Keeping with our sun there.

I'll pick up our Earth.

Our Earth has a particular orbit around our sun. It takes one year

and it's a surprisingly circular orbit around our sun.

But the distance of the Earth away from our sun is very important.

It's the right distance from the warmth of the campfire

that the temperatures on Earth are just right for life.

If the Earth was closer to the sun, perhaps like Venus or Mercury.

-Do we have a Venus. There we go.

-It would receive too much heat and now its oceans would've boiled away.

It would be a hothouse, greenhouse world, as we find Venus today.

If the Earth had formed further from the sun,

from the heat of the campfire,

-it would have frozen over and become like Mars.

-We come to Mars.

So, Earth is kind of in that sweet spot

between being too hot and close like Venus

and being too far away like Mars.

Earth orbits in this magical region, this ring around every star.

You can calculate it for different kinds of stars.

The temperature on planets orbiting within that inhabitable zone

would be conducive to liquid water and therefore possibly life.

It's those kinds of planets we're most excited to find.

-In fact, we've just found one.

-Yes, indeed.

The first planet in its habitable zone to be properly confirmed

was announced just a few weeks ago.

That was Kepler-22b - terrible name, but nevermind.

That was found by a different method called the wink method.

So, maybe I'll be the sun again.

Imagine this Earth-like world is Kepler-22b.

It can orbit in different ways.

You can imagine in any solar system just like our own,

you have all the planets orbiting at a particular plane.

Just by chance, some of these alien solar systems

will be inclined and angled directly towards us

from our telescopes on Earth.

So you'd see it orbiting around like this. From this point of view,

you can see the planet passing in front of the star, blocking out

some of its light as it transits or creates a mini-eclipse of that sun.

We know its radius, its size.

We know it's just over twice the width of Earth. We don't know its mass.

We think it could be up to 30 Earth masses,

if it's quite gassy, like Neptune.

In a best-case scenario, it might be all the way down to ten Earth

masses so it's still a super, a very heavy planet compared to our home world.

If it's a waterworld,

if it's covered in more ocean and less rock, it might be down to

ten Earth masses, but it will still have substantially greater gravity.

If there was life here, you'd be on an ocean world

and to support all your weight, like a whale, the water buoyancy

taking on that weight.

It's a wonderful thought, the whales of Kepler-22b.

I get sick of remembering catalogue numbers.

Kepler-22b I can manage, but Gliese 581b, C, D and E...

You have enough trouble with asteroids.

Exactly. If people named asteroids, there would be plenty of those.

-Would you name extra solar planets, Patrick?

-I would, yes.

-What would you call them? What's your first nomination?

-Nemo.

-Why Nemo?

-The unknown.

-OK. I like that.

I'm going for Chris and Lintott would be a good second one.

-For its moon maybe.

-Names are memorable and these are worlds.

There's a lot of imagination and they've got their own climates and atmospheres.

What was surprising though, and that's the recent discovery -

if you believe the results,

that everything we've been saying, all of these planets orbiting stars,

they may be in a minority in the galaxy or at the very least

there may be a whole other class of planet out there,

and these are the free-floating planets.

What can these worlds be like?

Well, they must be reasonably large to account for the signal we see.

They must be freezing cold,

cos they don't have star light.

What happens to Jupiter if you chill it down to minus 270,

-does it solidify?

-Not all the way through,

so the point about a lot of these free-floating planets

is that they've still got an atmosphere around them.

They've still got an insulating atmosphere, and so at the bottom of this it may still remain warm.

-Of course, they've still got their heat source.

-They've still got an internal heat.

Just like Jupiter and Saturn give out more heat than they receive.

So, perhaps even a super earth,

if it gets ejected to the cold depths of interstellar space

will cool down - it's atmosphere will condense onto the surface

but underground we've still got all that internal warmth being insulated

and possibly habitable conditions,

and so possibly these free-floaters are the most frequent habitable areas - the most frequent life-bearing planets in our galaxy.

The estimate I saw was that there might be a hundred billion of these things.

A hundred billion free-floating planets!

What strange astronomy these people must have.

If you could develop intelligent life on them...

Imagine if they did and they got to the stage we're at now

they would only now be realising

that there are planets around stars.

Which would be freaks for them, obviously.

We would be the anomalies of the galaxy.

That's a bizarre and slightly scary thought, don't you think?

We should talk about... Whenever we talk about extra-sol planets, there's something

slightly unsatisfactory that we can't see them.

We've got the wobble and the wink,

-but there's no real substitute for seeing these things.

-There isn't.

One of my favourite results from the last few years

was the first images of extra-solar planets.

-I agree on that one.

-Particularly...

I don't know if you can remember the Fomalhaut picture?

It looked like the Eye of Saruman.

The image looks odd cos you've got to mask out the light from the star,

but then you can see it move.

For me, that's real.

I say that I believe in these things once I've seen one.

-And now we have.

-That's right.

We've been talking about life as we understand it.

What about entirely alien life

of the kind you find in fiction stories?

Well as an astrobiologist you need to keep quite an open mind,

you don't want to get too blinkered

and think about only the things that we already know because as scientist

you want to keep your options open

and look elsewhere and look into other possibilities.

But I think, at least for the time being, as we're exploring Mars

and places like Eurpoa and Titan again in the not-too-distant future,

you want to be focused on what you know works.

We know that water-based life, and carbon organic life works,

and perhaps in the further future

if we don't find any organic life on a place like Mars,

we might want to think about exotic life on a place like Titan.

What about looking at the atmospheres of these planets

cos we're not far off the next generation of big,

REALLY big telescopes, might be able to take a very close look

at the atmospheres of these planets.

Will we be able to see if life exists from them?

In principal we could, so if we look at some of these Earth-like planets

that Kepler or other techniques we've been talking about

and can discover, and in the next five, ten years

we'll have a shortlist of Earth-like, habitable worlds

nearby us and we want to check them,

one by one, with next generation telescopes,

and look for signs of oxygen in the atmosphere.

I think the problem of whether there's life in the universe,

with the discovery of all these planets

and with the imminent discovery of Earth-like planets

of habitable zones in sunlight systems, I think has probably shifted

from being an astronomer's problem,

to being an astrobiologists problem or maybe even a biologists problem.

It's about what do we understand about evolution, how does life get started,

but it's all the more fascinating for that,

just a little harder to get the answers.

Patrick, we've been talking about these marvellous

discoveries from the Kepler spacecraft and just a few months ago,

I caught up with Bill Borucki who's the man behind it and he was fascinating.

Since 2009, Kepler spacecraft has been staring

at a small patch of sky monitoring 150,000 stars.

It's looking for tiny dips of light as planets

pass in front of those stars and it needs three of those winks

to be seen before the team can be sure they're onto something.

Bill Borucki is the leading light of the Kepler mission

and is proud to have discovered a multitude of worlds,

some normal, some exotic and strange.

I caught up with him at the recent planetary conference in France.

Of course, we have a lot of candidates and we go through

a lot of processing to make them announcements but the ones we've

announced firmly as planets, I think my favourites are the fact that

we now have one that has six planets orbiting it, transiting.

We have one where the planet orbits a pair of stars,

-just like in Star Wars.

-Oh, yeah!

You'd see two stars at sunrise

and two stars setting at sunset.

In Star Wars, you see Luke Skywalker looking into the distance,

you see these two stars setting on the horizon.

What Lucas got wrong was that he made the blue star small

and the red star big. Just the opposite case.

The blue star's the big one. The red star is small.

We talked to him about that. He said he'll try to get it right next time.

That's rather nice.

So, what this is telling us, really,

is that planets are rather easy to form, I would think,

if you see them around many stars and you see the diversity.

Is that the correct conclusion?

If we want to find an Earth around a star like the sun, if it's a small size, like the size of the Earth,

you can find that in a week or a month,

but a habitable sun where the temperature isn't boiling

then you have to have an orbit very much like the Earth's orbit,

you have to wait three years for those

but we are finding small planets,

and we are finding them around stars like the sun

but their orbits are too short.

We're beginning to think about how many large planets

and Earth-like planets there are.

Do we have a sense yet of which are more common?

Is a typical planet like Jupiter or are there more small rocky bodies?

All the evidence that we have is that the Jupiters are rare.

The Neptunes and the planets that are super-sized Earths

seem to be much more plentiful, like ten to one.

So that would be from a few times the Earth?

-When you think about these objects, you're asking are they rocky?

-Right.

If the planet's a gas planet, even though it's small, there can be

no surface and we don't think there's any life cos it's hydrogen.

-They have moons, though.

-It might have moons.

That's interesting.

We're finding a fair number of Neptunes

and Jupiters that in the habitable zone of their stars, but we don't

think there's life on the planet, but if it had moons, the moons

are round the planet and therefore, they are in habitable zone.

You can imagine that you had a Jupiter inhabitable zone

and had three or four moons like our Jupiter does.

They are all the size of the Earth.

They have atmospheres, people on them

and they go to places for vacations, or visit relatives and so on.

Do you have a sense of when we will have

a sense of what the population of planets are out there?

We still haven't got to the point where

we're finding Earths in the habitable zone.

We don't have a lot of confirmed objects in the habitable zone

so we certainly need more there.

People sometimes say, "You've found quite a few Jupiters now.

"Don't you have enough?"

It's like asking Darwin, "You've seen one finch.

-"Haven't you seen them all?"

-Yeah. Whereas, the variety is the point.

-The variety is the point.

Those differences tell you about their formation, their structure.

Well, in the meantime, more finches and I hope you'll come back

and tell us about them.

-Thanks a lot.

-I'll look forward to that.

-My pleasure.

Kepler has recently found Kepler-20e and -20f,

two rocky planets orbiting the same star, each roughly the same size

as Earth, but neither of them in that magic Goldilocks zone.

As the mission rolls on, discoveries like these means it's just a matter

of time before Kepler finds a planet like Earth, not too hot

and not too cold and then, the hunt will be on to see if there's life out there.

We've been talking about other planets, but how are they formed?

With me are the two Chrises.

This used to be so simple, we thought we understood how our solar system formed

but the presence of things like hot Jupiters and so on

have really confused the picture.

I think we need to start with star formation.

-Before you form a planet, you've got to form a star.

-Yes.

A star forms from a huge cloud of gas and dust and the general stuff

that's out in space and over hundreds of millions of years,

that collapses down just by gravity and the density

and the temperature get so hot in the centre that you form stars,

but that's just the centre cos you've still got this entire cloud of stuff around it.

Over, again, tens, hundreds, millions of years,

that flattens down into a disc of gas and dust, so no planets yet.

If I'm right, the tricky bit is going from dust to gas.

-Yes.

-All the way up to beautiful planets.

I'm going to give you a wooden spoon. No insult intended by that.

Stir the bowl in a nice, even manner.

The water in the bowl is the disc of gas that is orbiting the star.

-Is that the right speed?

-That looks about right.

We have some pepper and the pepper is going to be the dust

and we shall see what happens.

If you take the spoon out... The water's the gas.

I'm going to sprinkle some pepper on there and very quickly,

the grains of pepper group together into clumps.

They sort of do, don't they? It's a bit spiral-galaxyesque.

What happens to a proto-planetary disc, as we call them, is not

too dissimilar to what happens in a disc of gas and dust in a galaxy.

So why is the pepper clumping together?

Because the tiny grains stick together.

In a similar way to little grains of dust in a solar system sticking together.

I believe we now have our first ever image of a proto-planetary disc

-around Beta Pictoris.

-Oh, lovely,

and this is one of the ones that has planetary systems to it.

Yeah, so the first amateur image of a solar system

which has come out recently, which is quite amazing really.

And your own solar system in a bowl.

Chris and Chris, thank you very much.

We have planets on view this month and we still have.

Peter and Paul are waiting outside to show us Jupiter.

-Happy New Year.

-Thank you.

It's a bit of a wet, windy one and cold as well.

We were hoping to see Mars and Jupiter earlier, but I'm not sure now.

I've set up a pot of tea in the observatory so we can sit

and wait and see if the clouds part for us.

-Aren't you a good chap?

-I am indeed.

Some interesting things happening this year.

We've got that transit of Venus

and we have some good meteor showers this year.

The moon's out of the way.

I'm looking forward to the meteor showers.

They have been ruined this year

by the moon being in the way.

They've been awful.

We've also got the sun which is waking up at the moment.

It has looked quite exciting

and there's been lost of prominences and flares.

That is exciting because if it carries on building throughout

the year, that gives us the chance of seeing an aurora.

Let's start off with the planets

and the first planet which is Mercury.

A difficult object to see,

especially from cities cos it's always rather low down.

It's said only 1% of the population have ever seen it

and I don't think that's true.

It's probably much less!

It's pointed out month after month, but, during January,

it can be seen in the first part of January in the early morning sky.

If you look to the south-east just before sunrise,

you might be able to pick it up.

But much more prominently than that is the next planet.

Of course, the planet Venus, and quite good this year -

it's going to get reasonably high in the sky for the planet Venus

and it's one of those friendly objects for amateurs with all scopes,

or even binoculars cos you can follow the phases, really, with binoculars

and certainly with a large telescope.

You can, but the other thing about Venus is that it's so bright,

I mean, it can cast shadows, it's so bright

that with the naked eye it looks really stunning.

In fact, if you go right towards the end of January, there is actually

a lovely crescent moon very close to Venus in the twilight sky

and that's one of my favourite sights of all, I think.

Mars is at opposition in March so it is then visible all night

and well-placed for being able to see it.

It's actually not too bad cos it's not moving about a lot in the sky.

It's close to the rear legs

of Leo the lion.

It looks like a bright orangey star.

This time round, Mars' northern face is presented to us

so we get a good view of the north polar cap

and as it's now spring, that enormous polar cap is starting to evaporate

and fills the air with fogs and mists.

You get that interesting appearance to Mars.

One of the most prominent dark features on the surface,

that V-shaped dark feature, the Syrtis Major,

which I think always looks like a pair of Y-fronts.

-Says a lot about your imagination, Pete.

-Possibly.

Let's carry on out of the solar system now

and go to the biggest planet in the solar system, Jupiter.

Still blazing away in the sky.

It's been magnificent over the last few months,

but there's still plenty to be had with Jupiter.

It's actually in Aries.

I think it flips into the neighbouring

constellation of Pisces, just jumps over the border this month.

With the naked eye, it looks quite stunning.

With a pair of binoculars, you can make out those four moons,

the bright Galilean moons which dance around the planet

and then with a telescope, you can make out all manner of detail.

On the subject of Jupiter,

we have had a lot of wonderful images in to our BBC Sky Flikr site,

a lot of them illustrating what we've been talking about -

those really dark barges, the intense brown colour in some of them,

and of course the great red spot.

And that region of turbulence

which is behind the great red spot, it's an amazing thing.

t is, we're so lucky to have an enormous gas giant like that nearby.

Let's move onto one of my favourite planets of the entire solar

system and that is Saturn.

As you remember, there was that tremendous storm on Saturn.

We've never seen anything like it.

It appears it's still going.

The easiest way to find it is to use that familiar

pattern of the plough or saucepan.

-Yes.

-You follow the curving handle of the saucepan round,

you come to a bright orange star known as Arcturus.

You carry on going and you end up at Spica

and Saturn is right next to Spica.

In the constellation of Virgo.

This time round, now, Saturn has, again,

got quite a tilt on it now, about 14 or 15 degrees.

It's northern face is well titled so we're getting a really good view

of the rings and it looks quite pretty, I think.

It is quite pretty and if you've got a telescope have a look and see

if you can find that gap that's between the two bright rings.

It's a good test of seeing actually,

you should be able to see it in a six inch reflector.

OK, so let's move out from the solar system -

you have an interesting little deep sky thing for us.

Well, I think it's very sad, as we go into the spring months

because the gorgeous constellation of Orion

-rapidly disappears from view.

-It does, he's gone!

It gradually moves to the west and the encroaching twilight

swallows him up really quickly and we lose him.

If you go out towards the end of January, don't forget to go outside

and have a look at Orion hanging there in the night sky. Gorgeous.

Plenty to look at in the night sky in January, Pete.

We must have tea in the observatory more.

-I think it's getting cold.

-Let's try it.

And now for our News Notes.

Chris and Chris, what's happening in the universe?

Well, let's start close to home as ever, let's start in the solar system with Vesta

where we've got these amazing images coming back from the Dawn probe.

Which has been in orbit now for a few months.

In fact, it's just reached its lowest orbit which is

just 130 miles above the surface of this tiny little world.

And Vesta turns out to be an interesting place.

But the most remarkable thing is, down near one of the poles,

this giant mountain, nearly as big as Olympus Mons,

one of the largest in the solar system, on such a small world.

-I don't think that was expected.

-No-one thought about that.

Vesta's proved to be a big surprise

and some of the stuff we've seen happening on the surface -

little rockslides, landslides,

and the world is incredibly fascinating.

I was lucky enough to speak to Chris Russell,

the lead scientist of the Dawn mission, back in October.

The Dawn spacecraft went into orbit around Vesta in August 2011,

and is giving is a unique view of the solar system's second biggest asteroid.

I caught up with Professor Chris Russell at a recent planetary science conference.

Chris is in charge of the mission

and is loving the surprises Vesta is throwing at us.

We've learned it was a good place to go to.

And that's important to me,

because we're trying to go back in time

and to learn more about the earliest part of the solar system.

So, did the surface record all of these events?

We believe, when we look at the surface, it's been a good recorder.

So this impact crater is about the same size of Vesta itself.

Its diameter is comparable to that?

It's very large, we're trying to understand things like,

what is the age of this structure?

Is it more recent than the other surface or not?

We haven't figured that out because there are some areas

that don't look like they have enough craters.

But in general, surfaces with fewer craters are considered young?

Young, and the ones who are heavily cratered are the old ones.

And, we think we can use the cratering record

to figure out how old the surface is.

Dawn has seen more recent features too such as landslides,

but the scientists are also looking for craters being formed today.

One of our team members asked us just before we got there and said,

"could everybody keep their eyes open for fresh craters

"that appear while we're in orbit.

"Take a look at those images when we get there

"and take a look at the images just before we leave and see if anything happens."

So we might get one so we should be keeping our eyes open.

Craters expose what's underneath the surface and the fresher the better.

Looking at craters on Vesta is our way of seeing what the solar system

was made of 4 billion years ago.

And seeing something for the first time is always exciting.

When you see something in high resolution

you've never seen before, you're surprised.

Your imagination is great but you can't

imagine what the surface is going to be like.

The team is doing a lot of thinking right now and exchanging ideas.

Sort of like a bunch of kids at Christmas.

Open a present and say "Look what I got here."

And then they share and then they opened something else up and share the information.

Dawn will explore Vesta until later this year,

and then it's on to pastures new at the solar system's largest asteroid, Ceres.

Where no doubt, we'll be surprised and amazed yet again.

There's one other story we have to mention this month, Patrick,

and that is the first image from a rather obscure camera called SCUBA-2

which we featured on The Sky at Night a few years ago.

It's an enormous thing cos it has to be cooled right down cos

it's going to look in what we call the sub-milimetre -

the region of the spectrum that allows us to look at some of the coolest things in the universe -

the places where stars are about to form. They've had a huge struggle,

it's incredibly technologically complicated,

at one point they couldn't even get access to their camera

cos somebody else in the laboratory had poured plutonium down the sink,

or at least there had been a spillage,

they just had horrible luck

and so I've got to show you this image

which is the first results form SCUBA-2:

You've got the optical image there

and then filling in the gaps the detection of light

from this wonderful camera which is going to help us understand

star formation and these dark galaxies.

Of course, we can always find more news on the website:

You'll also find newsletter 124 which you wrote with Pete Lawrence

about what to see in the sky.

Thank you both very much.

Next month, I will be talking about infra-red astronomy.

Until then, good night.

Subtitles by Red Bee Media Ltd