Dawn at Vesta The Sky at Night

Good evening.

Now, this programme is going to be about asteroids

and not everyone will know what they are.

Well, asteroids are comparatively small worlds

going round the sun in the same way that we do,

many, though not all, between the paths of Mars and Jupiter.

And, telescopically,

they look like stars, but they are certainly not,

they are quite different.

Only one, Ceres,

is as much as 500 miles across,

and only one, Vesta,

is ever visible with the naked eye.

Well, to talk about those, Chris Lintott, back from America

and one of my old friends, Alan Fitzsimmons.

Alan, the Dawn probe has been sent up

and is now orbiting Vesta.

Can you take us through the Dawn probe, tell us what it is?

Well, it's a fantastic mission.

It's a mission to visit both Vesta and Ceres,

as you've mentioned already.

It's in orbit now, about Vesta, successfully,

and for the next year it's going to be studying, in great detail,

this amazing world, which we believe

has been there, roughly in the same place,

since the dawn of the solar system.

And it's going to give us clues

as to how the asteroids evolved over that time.

And we've got some amazing pictures of the kind we've never seen before.

Let's have a look at them.

Well, I mean, these are fantastic images.

We've had some very low resolution shots

taken by telescopes on Earth, and, of course, by the Hubble telescope.

But these show the detail

that, really, the Dawn mission was designed to provide.

Mountains, valleys and craters.

Absolutely. And many of the views of course at the moment

just of the southern hemisphere of Vesta,

because as Dawn approached the asteroid

it came up really from below to get into orbit.

And that was particularly important for us

because what we're seeing

in these first ever close-up images of Vesta

is the sign of a tremendous impact

that happened possibly 3.5 billion years ago,

that literally shook this small world to its very foundations.

I have to say, I have trouble picking out an impact crater on this image.

Which of these craters is the impact crater that you're talking about?

The reason that... In actual fact, I think we all have problems here,

because here we're looking at a crater that's about the size of the body we're looking at.

-The whole image is almost a crater.

-Absolutely.

So when we look at this, we see this huge mountain facing us

that's probably about 15 to 20 miles high

and about 50, or even 100 miles across.

So that's what? Three times Everest, if you scale up to Earth size?

-Absolutely.

-Wow.

About the size of the largest volcano on Mars, Olympus Mons.

And that is, in fact, the central peak of the crater.

-So this is material that was thrown up and came back down?

-Absolutely.

And then surrounding it,

out to about the radius of the asteroid itself,

is the depression of the bowl of the crater.

So on the right there, you can almost see those might be

the walls that were once the walls of the crater, I guess?

Absolutely.

-Scattered bits in all directions.

-What we now know from telescopic studies,

in the 1990s and since then,

is that around Vesta, in the asteroid belt,

are fragments of Vesta.

Some of these fragments of Vesta have actually arrived on the Earth

-and I'm glad to say we have one with us now.

-Absolutely, Patrick.

And here it is.

In meteoritical terms, this is called a eucrite,

or a eucritic meteorite,

and there's two things you can see when you look at this.

First, we can see it's composed of very angular, small, dark fragments,

these are the fragments of original basalt

that have been compressed into a rock by...

by, literally, other rocks falling on top of them

due to other impacts.

Second thing you notice

is that you don't see any glittering due to metals.

-No.

-And quite often,

as you know, when you find meteorites,

-they're highly magnetic...

-That's right.

-..because they contain lots of iron and nickel.

-This one's not.

Absolutely not. And that's of course because Vesta was differentiated

and formed its iron core when it was molten.

All the metals sank down into the centre of body, by and large,

so this is relatively metal-poor

compared to an ordinary meteorite that we would find.

So these two clues tell us that it came from a volcanic body.

So it's amazing to think that here, in the studio,

we're actually seeing and touching

a piece of another world so far away.

Absolutely, and, of course,

some might say that if you know so much about it,

if you've already got a piece here,

why do you need to send a spacecraft to Vesta?

-Ah, that's another story!

-That's right.

In fact, it's BECAUSE we have this

that we know it's worthwhile sending Dawn there in the first place.

The mission's "Dawn" because we're getting a trace of the early solar system,

but can you give us a potted history of the solar system?

We start off with the sun forming and a disc of material around it,

and then what happens next?

What happens next is somehow, magically,

the solar system comes into being.

And I use that phrase almost literally,

because we now have some fairly sophisticated models

-of what happens...

-Computer models.

-That's right.

We can't, unfortunately,

make our own solar systems just yet in real life.

But these models imply that it was a very turbulent process

in taking this disc of gas and dust

and creating a planetary system out of it.

Because it's turbulent, we have things flying all over the place.

You've only got to look at the surface of the moon

to see that, as Patrick knows.

But what's happening to Vesta at this point?

We believe that Vesta was one of a population of very large objects -

several hundred miles across, up to -

that were formed at this time,

but most of them have been lost in the subsequent history.

They've suffered collisions. They've been broken up in those collisions.

Or they've simply been ejected from the solar system,

or destroyed by a collision with the sun or another planet,

and so, when we visit Vesta,

we really are looking at the last survivor from that epoch

where the solar system was sorting itself out.

We know that the probe is now going round Vesta

and sending back amazing pictures and vast quantities of data.

Well, eventually, it's going to break free from there

and go on to the larger asteroid, Ceres,

which is fainter because it's further out,

but about 500 miles across.

Now, Ceres and Vesta are very different, aren't they?

Ceres, although it would have been heated during formation,

as Vesta was, and it should be differentiated,

it should have a core mantle, even-crust structure,

as Vesta has, but because it's so far from the sun,

its composition was much more dominated by lighter elements,

so the rocks on Ceres are much more dominated by,

for example, carbon and hydrogen and oxygen,

and, indeed, we believe that within the rocks of Ceres

there has been the action of liquid water in the past.

And so, if we want to think of Ceres

as anything special, we would think of it as a water

or at least ice-dominated asteroid.

Any ideas of landing on Ceres?

Well, that's a possibility, of course,

just as the NEAR Shoemaker spacecraft landed on Eros.

More or less by accident!

-Yes. I mean, it wasn't designed to land.

-At the end of its life.

That's right. Now perhaps the best option

is that there will be enough fuel left onboard

to fly Dawn to another, third asteroid.

There would not be enough fuel to go into orbit about it,

but we could have another fly-by of yet another unexplored world.

Well, Vesta was fascinating,

and before long we're going to hear a great deal more about it.

Chris, Alan, thank you very much.

Well, quite apart from the big asteroids,

there are many, many smaller ones,

some of which come surprisingly close to the Earth.

And one did so quite recently.

Paul Abel has been talking about these near-Earth objects.

We all lead busy, hectic lives and the thought of an asteroid

coming at us from the depths of space

isn't something we worry about a great deal.

We go to bed at night and presume our civilisation will be there in the morning.

But there are some big asteroids out there

with the potential to do a lot of damage,

and some of them pass dangerously close to the Earth.

In the sleepy Berkshire village of Great Shefford

lives an astronomical sentinel.

By day, Peter Birtwhistle works in IT,

but by night, he is a defender of the Earth,

scanning the skies for asteroids.

Peter took this footage of Asteroid 2011 MD back in June.

It was the size of a double-decker bus

and passed just 7,500 miles from the Earth.

It looks so close you could touch it.

-Hello, Peter.

-Hello.

Oh, this is a most impressive set-up you have here.

So, why don't you tell us, then, how did you get involved with 2011 MD?

Well, I was out observing that night,

following near-Earth objects that I'd normally do anyway,

and the discovery was announced about three-quarters of an hour before dawn,

which gave me just enough time to try and find it.

You must have been elated when you found it?

It was one of a couple of objects put on at that time,

and I chose that one to try and go for it.

I just had enough time to do so.

It wasn't where it was supposed to be, so I had to chase it a bit,

and it was great. By the time I found it, it was just in the nick of time -

the clouds were rolling in, the dawn was coming up.

Yes, I know that feeling very, very well!

So, you found the object, what did you do then?

Well, as I normally would,

I just had a look to see where it was going in the next few days.

I used the discovery positions that were obtained in America,

together with mine,

and it worked out the orbit which showed

that it was going to make a really close pass to the Earth in about five days from then.

Did you feel, "Oh, my word! This is the end!"?

Not quite, but it was exceptionally close.

-It was, yeah.

-Right from the very beginning, from that recovery of it,

it was obvious that it was going to be very close.

It's always exciting when that happens.

There are around 8,000 near-Earth asteroids out there -

too many for professional astronomers to track.

Amateurs like Peter play a valuable role pinning down these astronomical vermin.

That could prove vital if one were heading for us.

In actual fact, what size objects really pose a danger to the Earth?

Well, a big problem would be a kilometre-diameter-size object.

-That would cause quite a catastrophe on Earth.

-Right.

There are a number of those that have been discovered, near-Earth objects,

but all of those have been observed enough to know

that they won't hit us in the foreseeable future.

But there is a great potential for material out there?

Well, there are a lot of smaller ones.

-Smaller ones, 100-200m across, can still cause regional problems.

-Right.

Our last regional problem happened in 1908

when an asteroid hit Siberia.

It flattened 100 million trees over an area of 2,000 square kilometres.

That's the equivalent of everything inside the M25.

And I have to ask, if you should discover a tremendously large asteroid heading our way,

what would you do? I'd go down to the pub.

OK, no. I'd try and get another few positions on it.

-Dedicated to the last. Peter, thank you very much.

-OK.

Some time ago, somebody came to me and said,

"What would you advise me to do if I saw a mile-wide asteroid

"heading straight for the Earth on a certain collision course?"

I said, "I'd recommend this -

"repeat very slowly after me, 'Our Father...' "

And that's as far as I got.

At least there's plenty to see in the sky,

and Pete and Paul are outside waiting for us.

Well, Pete, only a few hours of darkness at this time of year,

but, nevertheless, plenty of things to look at.

-There are. In August, you really have to cram your observations in.

-Yes!

So, what do you think we should look at first?

Well, we've just been talking about the Dawn mission to go and see Vesta and Ceres,

so why don't we try and locate where Vesta and Ceres are in the night sky?

-Amateurs can see them with just a pair of binoculars or a telescope.

-Indeed.

Here we are, Pete, with Patrick's 12.5 inch reflector.

One of my favourite telescopes here, actually.

It's the one I normally use. But you don't need a telescope as vast as this to see Vesta, do you?

You don't at all. Vesta is actually the brightest of the asteroids

and you can see it in a pair of binoculars fairly easily.

At the moment, Vesta is actually coming to opposition.

It comes to opposition on 5th August.

-So it's opposite the sun in the sky?

-That's right.

That's the time when it's at its brightest,

and this is a particularly good opposition of Vesta,

because it will be bright enough to be seen with the naked eye.

If you're in a dark sky.

It's slightly brighter than Uranus, not by very much,

but it is slightly brighter than that.

A telescope will show its disc, won't it?

If you've got a big telescope, it has got a tiny disc.

But really, binoculars are the way to just get a glimpse of it.

At the moment, it's in Capricornus -

-the Sea Goat.

-But that's not what you've called it.

It's a bit like a misshapen triangle,

but to me, it always looks like a misshapen sandwich.

It ends the month very close to the star Psi Capricorni.

Oh, very nice. So some easy pointers to find it then.

Vesta, of course, not the only asteroid we have in the night sky.

We also have Ceres,

named after the goddess of cereals!

So it is, yes! Ceres WAS the largest of the asteroids.

It's been reclassified now as a dwarf planet.

What will it be next week?!

It's actually quite a lot fainter than Vesta,

and you will need a pair of binoculars or a small telescope

with a wide-field eye-piece will pick it up as well.

But it's in a rather obscure part of the sky.

It's in Cetus, isn't it, the Whale?

It is. It's quite close to the tail of the Whale.

The tail is marked by the star Diphda, or Deneb Kaitos.

-It depends what you want to call it.

-I prefer Diphda.

"Diphda" means "frog", actually. "Deneb Kaitos" means "whale's tail"

-so Deneb Kaitos is more appropriate.

-OK. And this is where we can find this asteroid?

Yeah. It's moving in quite a small arc around that region,

so, again, you will need to use optical assistance to find it

-cos it's fainter than naked eye threshold.

-We don't just have

dwarf planets and asteroids. We also have the other planets,

-and Mars is making a comeback.

-It's been gone for ages.

-I really miss Mars.

-It's returning into the morning sky now.

So there's a couple of nice events to look out for, isn't there?

Mars is moving to the south of a rather lovely open cluster

known as Messier 35 in Gemini.

Now, have you ever seen Messier 35?

-Possibly by accident!

-THEY LAUGH

It's a really nice open cluster. In fact, it's a very strange open cluster

because there is a pattern of stars in there

that draws the outline of the Space Shuttle coming in to land.

-Really?

-Trust me. It does.

-You didn't just make that up?

-I didn't.

If you have a pair of binoculars and you look at M35,

or at Mars, rather, which will be the brighter object,

then M35 will be above it on the morning of the 7th of August.

-That's well worth going to look at.

-However, moving on

from a planet with not much detail on cos it's small to the enormous planet Jupiter.

This is making an enormous comeback.

Over the next few months,

there's going to be one word which will sum up Jupiter,

and that will be "wow"!

It's going to be an incredible sight for us.

It will, and we have some interesting satellite phenomena,

so its largest satellite, Ganymede...

The largest satellite in the entire solar system.

-Bigger than Mercury.

-It is, and if you go out on the mornings

of the 7th, 14th and 21st of August, you'll see Ganymede passing

in front of the Jovian disc,

which we call a "transit",

and Ganymede and its shadow passing

in front of the disc is quite a spectacle.

It is. That shadow, when it's on the disc, is incredible.

-It's so round and dark.

-It is very black.

It's so hard to miss it. I've seen it in a four-inch telescope -

a beautiful thing, and I'm very excited to have Jupiter back

because it's been in the murk for all these years, and now it's coming back, and climbing higher.

It will be about 50 degrees up at its best,

and that's incredible.

The view we're going to get of it will be amazing.

Well, all these wonderful things

to squeeze into the few small hours of darkness in August,

-so I think it'd be interesting to go and look at some of those things.

-Mm.

Pete and Paul, thank you very much.

Back in my study with Chris North and Chris Lintott.

I'll begin, if I may. A new satellite of Pluto

has just been discovered.

We knew of three - the big one, Charon,

and two small ones, Nix and Hydra.

This new satellite is small - 20km across.

There it is. A name has got to be found for it,

presumably something to do with the underworld.

Well, my suggestion is Thanatos, after the god of death,

but I wonder what viewers think,

so we invite viewers to send in their ideas

about naming the new moon of Pluto.

So, there we have the outer solar system,

but what about the inner planets? Mars back in the news?

Yes, we talked last month about the sad death of Spirit,

which has now been abandoned on the surface,

but its twin, Opportunity,

roves on. It's just passed the 20-mile mark, would you believe,

for a mission that - we say all the time -

was supposed to last 90 days and it's now gone more than 20 miles

and it's approaching Endeavour crater,

which is this deep crater that we've been waiting a long while

to get a look at, so the Opportunity is about to get very exciting.

And we also have Curiosity, which is the next probe to Mars.

It's the size of a big car,

and it's going to do fabulous things and that's been shipped from JPL

in California, where it was assembled, over to Florida,

ready for launch later this year.

What about the landing site on Mars?

The choice is a wonderful crater called "gaul" or "galle",

I'm not sure which.

-Gale!

-Well, I was close. So, Gale crater,

and the thing about Gale crater is it's much deeper than anywhere

we've visited on Mars before

and that means you can get much further back into the history of the Martian past,

so fingers crossed for a safe and rather rocky landing

and then we'll get to see a lot more of this part of Mars.

Where next, then?

We want to go a lot further out. We want to go out

to the Large and Small Magellanic Clouds.

The Large Magellanic Cloud is 160,000 light years away.

It's a small galaxy that orbits our own Milky Way galaxy.

And the Large and Small Magellanic Clouds

appear to have a very mixed past. It's something we don't understand.

The stars seem to have been shared between them somehow,

-so this is a study of the stars in the clouds.

-This is a new result. It turns out that about 5% -

so one in 20 of the stars in the Large Magellanic Cloud -

don't look like Large Magellanic Cloud stars,

but look like their cousins in the Small Magellanic Cloud.

So the stars must have been swapped,

and that must have happened relatively recently,

so these two galaxies, as they orbit the Milky Way,

must have been interacting with each other, grabbing each other's stars,

-and I think it's telling us that the area around our own galaxy is quite a complicated place.

-Oh, yes.

We don't quite understand the history of anything we see around us, so that's rather fun.

-What else do you have for us?

-We've gone from the Large Magellanic Cloud

to something very close to home, which is right behind me here. This is a new award

from the Royal Astronomical Society that I think you've seen already.

This is the Patrick Moore Medal, which is not FOR you.

It's for the teacher or educator

who's done something remarkable to inspire interest in astronomy,

and so the Royal Astronomical Society

have asked us to tell people to send in their nominations for this award.

Why name it after me? Many people have done so much more than I have.

-Well, you inspired Chris and I. Right?

-Yes.

It's very easy to nominate people. You can go onto the RAS's website.

And you can nominate the person or the teacher who's inspired you most

in astronomy or geophysics. There's one last news note,

and that's some worrying news from the States -

Congress are considering cancelling the James Webb Space Telescope.

-I heard about that. I can hardly believe it!

-Yes.

It will be a disaster for the future of astronomy.

A short while ago, I went to the Rutherford Appleton labs

to take a look at one of the instruments being built in the UK to go on the Webb space telescope.

The Rutherford Appleton lab in Oxfordshire

is where they design and build telescope instruments.

The latest is the Mid-Infrared Instrument, or MIRI.

It will soon be fitted onto the world's most ambitious satellite,

the James Webb Space Telescope, or JWST.

Before it can begin its long journey, it has to be tested

to withstand the conditions it will encounter in outer space.

'To get close to MIRI,

'I have to put on this attractive bunny suit.'

I don't think I've ever been so clean.

This is the test chamber, and, inside,

MIRI is being subjected to the harsh conditions of space.

What we have here is its twin sister.

Light comes in from the massive telescope to this part down the bottom.

It's fed up to the camera, where the images are taken,

and a small amount is sent up to the spectrometer,

where the light is spread out into its range of wavelengths,

so we can pick out specific types of element and molecule

and work out what the chemistry is like in outer space.

The JWST has a mirror 6.5 metres in diameter

and will look at longer wavelengths than Hubble.

This allows it to see cooler objects, providing astronomers

with views of the formation of galaxies, stars and even planets.

'Professor Gillian Wright has been involved with designing MIRI

'and the JWST since the 1990s.

'It has taken a life's work to help construct

'the replacement for Hubble.'

It differs from Hubble in that it's a much bigger telescope

and we know from the discoveries that have been made

in the Hubble Deep Field

that galaxy evolution happened

much earlier in the evolution of the universe

than we knew before Hubble, and so what we would like to do is study

those more distant galaxies and to do that,

we need a much bigger telescope,

so that's where JWST will follow from the science

that's been done by Hubble with new science in complementary ways.

One of the reasons we built MIRI

was to try and learn more about how planets form around stars

and also about how stars form,

because we know that stars form in very dusty regions

and so, somehow,

the chemistry of the dust is all tied up in this process in making it work.

Taking images in the infrared is technically challenging.

With a million pixels, MIRI's mid-infrared camera

is the largest ever built.

Infrared astronomy has come a long way in just a few decades.

When I started as a mid-infrared astronomer,

we had one pixel and that was the best detector you could get!

Detector technology has changed a lot,

we know how to do big telescopes in space now,

with Herschel and JWST

and so people talk about this now as becoming the era of the infrared

because a lot of the cutting-edge discoveries

we expect to come from working at these longer wavelengths.

Getting MIRI ready for its voyage means testing everything will work

in the cold, hard vacuum of space.

Here we are in the MIRI test control room

and we've got on the screen real data from MIRI

in its test chamber. What are we seeing here?

This is the data from the MIRI imager channel

looking out at the test chamber,

and it's looking at a tiny point source here

which we're using to simulate a star.

Because we're looking in thermal infrared wavelengths,

you can also see on the image all the structure

that supports that simulated star.

So it's looking at something that's the same temperature

as a cool, brown dwarf, something like that?

Something about 800 Kelvin, yes, or a very cold star, maybe.

The JWST is pioneering technology and is technically ambitious.

Its final destination is a million miles from Earth so,

unlike Hubble, astronauts won't be able to repair it

if something goes wrong.

No-one's ever done a telescope with optics this accurate

and put it in space before, and it's not really so many years

since we learned to do telescopes this size on the ground

and now we're trying to put one in space, and it's also ambitious

because it's cooled by a sunshade

and no-one's ever really done a mission which is so totally reliant

on the sunshade for its cooling,

so it would be the first time that's done as well.

And it's deployed, because it's too big to fit in a rocket,

so we have to unfold the telescope in space.

In the next few weeks, MIRI will have completed its tests

and be shipped to NASA to be fitted onto the spacecraft.

However, with budget problems in the US,

there is a real threat that the JWST could be scrapped.

If this happens, the loss to us all would be profound.

The chance to understand our universe closed for decades.

So let's only hope that common sense prevails.

Meanwhile, we've had some lovely pictures sent in and some here of noctilucent clouds

and these are really beautiful.

They're incredible. One of the best things

about observing in the summertime, I think.

If people want to send in their own images for us to look at or to use

on the programme, they can do so

on the Flickr section of our website at...

And we have some wonderful images there, but the image

I'll be staring at this month

is this one from the Herschel space telescope.

It's an infrared image of our own galactic centre,

and, if you look carefully,

you can see this twisted loop of material around the centre itself

and it's really quite difficult to explain why that material's there,

or why it's in this twisted form, so I shall be staring at that

and wondering for most of the next month.

-I am quite sure you will.

-And the image I've picked out

is one from orbit around Earth,

an image by an astronaut on the international space station,

and what's stunning about this is quite how much is in there.

You've got the solar panels of the space station,

you've got a part of the space shuttle Atlantis,

you've got the Earth and the aurora in the atmosphere

and then you've got some of the star clusters and stars towards the centre of our galaxy.

This is one of the last times we'll get an image

with the space shuttle in orbit.

Thank you both very much.

When we come back next month,

we'll be talking about the future of space exploration

and we'll be joined by astronaut Piers Sellers,

so, until then, good night.

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