Comet Chasing The Sky at Night

This month, we've travelled to

one of the best observing sites

in the world. We're on La Palma in the Canary Islands.

We're here to chase comets and in particular Comet ISON,

which has been getting a lot of attention

because it might be really spectacular

as it slingshots around the sun in just a few days' time.

And that's not all. There are two other comets that are bright

in our night sky at the moment, and we'll be using these telescopes

to track down these enigmatic explorers of the solar system.

But first, here's Pete Lawrence with his guide to what else can be seen

in December's night sky.

The magnificent constellation of Orion is prominent this month,

best seen around midnight

at the start and end of December

when the bright moon is

out of the way.

The three stars that form his belt

are very distinctive, and from them,

his fainter sword can be seen hanging.

Look at this with a pair of binoculars or small telescope

and right in the middle, you'll find the Orion Nebula,

Messier 42.

This is a huge cloud of glowing gas,

a place where new stars are being formed.

Follow the belt down and left

to locate the brightest night-time star of them all, Sirius.

Above and slightly left of Sirius

lies Procyon,

a bright star in an area of sky bereft of much else.

Draw an imaginary line

from orange Betelgeuse in the top left of Orion

to Sirius, on to Procyon

and back to Betelgeuse again

to form the Winter Triangle.

The charts to find everything mentioned here

can be found on our website.

The Sky At Night has come comet-chasing

to the volcanic island of La Palma in the Canary Islands.

It's a week until Comet ISON

has its close encounter with the sun.

The volcano dominates everything and at 8,000 feet,

the astronomical observatories sit well above the cloud layer.

The Roque de los Muchachos, or Rock of the Boys,

is named for these volcanic remnants up at the top.

The Sky At Night team have joined us, and we've got a special guest,

Alan Fitzsimmons, from the Queen's University, Belfast,

a world expert on comets.

From up here, you can see why astronomers have been coming

to this site for decades. The clouds are far below us,

there's a beautiful dark blue sky above us and we've been given

the run of not one but two telescopes to go comet-hunting this evening.

Comets are the primeval relics of the solar system.

They're the leftovers from when the planets were formed.

These pristine bits of four-billion-year-old ice and dirt

also have complex molecules, such as alcohol, cyanide and ammonia.

Our special comet is called C/2012 S1 ISON,

named after the telescope team that discovered it last year.

ISON has come from the very outer regions of the solar system,

from a place called the Oort cloud.

It's passed by Earth and is on a slingshot around the sun,

getting within one million kilometres of the sun's surface

before being flung back into outer space.

Alan has been looking forward to seeing Comet ISON

since it was first spotted last year.

There's two aspects to ISON

that make it a really special comet.

The first is that it's its first time in from the Oort cloud.

It's spent 4.5 billion years, as far as we know,

out there in the depth of space,

almost, effectively, interstellar space,

and it's coming in for the first time.

Now, we see many comets each year

that are coming in from the Oort cloud, probably for the first time.

However, Comet ISON is also going to pass very, very close to the sun.

It's a sungrazer.

And we've never had that combination of features

for a comet in modern history.

And so, right now, as it approaches the sun,

Comet ISON doesn't know what's in store for it.

It's just behaving like a normal comet would the first time

it comes in from the Oort cloud.

But as we stand here, in just over a week's time,

it's going to be under the full force of the sun's heat.

That's 1.7 solar radii from the surface of the sun itself

and that, we hope,

will reveal immensely interesting aspects,

not only about the make-up of comets but how they're put together.

Comet ISON is too near to the horizon for the big telescopes

to look at, but we're incredibly lucky

because there are a host of other bright comets we can choose from.

It's a very special time for comets.

We have ISON itself, of course,

but we also have Comet Brewington,

which is a short period comet, going around the sun.

It only orbits the sun once every 10.8 years.

Then we have Comet Lovejoy, which is the brightest comet in the sky

as we stand here on La Palma,

and it's actually really, really nice.

It's quite high up in the sky,

in the early morning sky,

and it's something we can easily observe.

With brilliantly clear skies up above La Palma, we're planning to

make the best of them and that means we've got a long night ahead of us.

We're going to start the evening by looking for Comet Brewington,

just after sunset.

Then, around 4am, we'll look for Comet Lovejoy,

before we finish with Comet ISON just before dawn.

It's a busy schedule and it's rather ambitious

and so we're going to split up into two teams.

Should make for some healthy competition.

Well, this is our telescope for tonight.

-This is the Liverpool Telescope.

-And we're ready for it, aren't we?

Bring on those comets.

Chris and I have been given the keys to the Isaac Newton Telescope,

one of the most venerable of the British telescopes on the island.

And while it might not be as modern as some of the other telescopes

here on La Palma, tonight we've been given use of a scientific

secret weapon...a spectrograph.

This is real science, and Alan is going to help us understand

and interpret our results.

Pete and I are looking forward to the challenge

of imaging our two comets.

The Liverpool Telescope

is the largest fully robotic telescope in the world.

Everything is pre-planned, and professionals, schools

and amateur astronomers can use it.

Mike Bode is the telescope director.

-Hi, Mike.

-Hello, Mike, great to see you.

-Welcome to the Liverpool Telescope.

-Thank you very much.

A comet-hunting group recently imaged ISON with

the Liverpool Telescope.

Now, Mike, this is a robotic telescope.

So, how does this one differ to the other ones on the island?

Our philosophy of operating this telescope is like

a space probe on the ground.

So, during the night, there's nobody looking after it, there's nobody

interfering with the schedule, and so on, it's all automated.

So it's got a whole list

of objects in its scheduler that are important to do scientifically

or as part of the programme we do for schools, and it picks them

at the optimum one to observe next.

But we've plumbed in a few observations

especially for you that are going to be done towards

the beginning of the night when we'd normally be doing

some calibration things, while it's still twilight.

Alan, Chris and I are using the Isaac Newton Telescope,

which started work on La Palma in 1984.

In telescope terms, it's well into its middle age

but it's still hard at work.

-Here we go, look at it.

-This is more like it.

It's a beautiful, beautiful telescope.

The two comets we're looking at have significant differences.

Comet Brewington takes 10.8 years for an orbit, and it's been making

regular trips to the inner solar system for over 100,000 years.

It's been heated up many, many times.

Comet Lovejoy takes around 10,000 years to go around the sun

and so it's only been round a handful of times.

It's younger, and it should be fresher.

They both share the characteristic look of a comet,

with a head or a nucleus, and a tail that streams off into the distance.

So, the nucleus is the frozen, dirty stone ball.

Icy dirt ball, depending on your point of view,

that's been out there, frozen in deep space, either in

the Kuiper belt or the Oort cloud for 4.5 billion years.

And as it's warmed by the sun, as it approaches the sun,

the surface ices evaporate or, rather, we say they sublimate

because they turn directly from a solid into a gas.

And that streams outwards from this actually relatively tiny nucleus.

Most of the nuclei of comets are only a few kilometres across.

Smaller than the island that we're standing on!

But when those gases expand outwards, they form these

temporary atmospheres that are much, much larger than

the Earth...approaching the size of the sun.

By studying that released atmosphere around the comet, we actually

figure out what's buried in the really invisible

nucleus in the centre.

Some students are here to help us

and to get invaluable experience at chasing comets.

It's not an easy task while they're speeding around the sun.

The spectrograph the students are preparing will measure

the reflected light from the comet,

as well as the light from the gases in its coma.

The instrument masks off most of the comet,

leaving a narrow slit of light, which is then spread out into a spectrum.

Every type of gas has a different spectral fingerprint, and we can

use that to identify the gases in the atmosphere of the comet.

And that's something that this study of comets really tells us,

because these are the leftovers of the formation of the solar system,

so whilst they're changing as they come into the sun, and giving off

all these gases, they do let us probe what was going on

4.5 billion years ago when the planets and the comets and asteroids

were all forming. It's a real insight into the history of the solar system.

Absolutely. If you think about it,

it's a primordial Rosetta Stone

going back 4.5 billion years.

We're seeing material that has never seen the light of day since then.

It's been locked up inside a comet,

and now it's been released for the first time

and, hopefully, we'll get some really nice data on it this evening.

The telescopes have their targets and they're ready to go,

but while we wait for night-time,

Paul Abel's gone to see the biggest British telescope

here on La Palma.

Behind me stands the William Herschel Telescope,

which, when it was built in 1987,

was one of the world's largest optical telescopes.

Today, it's still at the cutting edge of research in astronomy.

Patrick Moore and The Sky At Night

followed the astronomical progress on La Palma,

especially the building of the William Herschel Telescope

in the late 1980s.

When you're building a big telescope,

I suppose about 50% of the problems are engineering,

and the other 50% are optical,

and obviously, the main component, optically,

is the big mirror of the telescope.

Now, this mirror is 165 inches,

or 4.2 metres, in diameter,

and it weighs 16.4 tonnes.

There are only two telescope mirrors larger than that -

the Russian 236-inch,

which, frankly, isn't very good,

and the Panama 200-inch, which is now 40 years old.

Now, the mirror itself has got to be amazingly accurate.

We are talking about accuracy to something like 1/40th of a micron.

And you can imagine how difficult that is.

And, believe me, this mirror is going to tell us

a great deal about the universe that we don't know at the present time.

The William Hershel Telescope lived up to that promise.

It revealed many insights into the expansion of the universe

and observed the first optical gamma ray burst.

Today, it is still at the forefront of research.

Exoplanets are the new holy grail for astronomers,

and a team using the telescope

have developed a new and novel way to find them.

Tonight, the team of astronomers in the telescope will be using

a technique called polarisation. By using a filter like this,

they will be able to remove the starlight

and examine the dusty disc which circles the star.

The team using the telescope is led by Christoph Keller

from Leiden University in the Netherlands.

We'll go in through here.

You come after me. OK?

Ah! A secret, magical door.

Brilliant!

Ah...yes.

-Here we go. After you.

-Thank you, thank you.

Oh, this IS impressive. It looks like a giant Meccano set.

Here we are.

The idea here was to take commercial components and put them together

in ways that nobody had done before.

It's cheap, it's relatively fast,

but it requires us to build this up from scratch every time.

Perhaps you could explain, then - we have a light from a star

with a dusty disc around.

How are you going to take away that starlight

so that we just end up with the disc?

When you have light coming from a star, it's unpolarised.

-There is no preferred direction in which the light goes.

-Mm-hm.

When you have dust or a planet or something else around the star,

then the light from the star

-reflects off this material and then comes to us.

-I see.

-And physics tells us that the light gets polarised.

-Right.

So what we measure is the polarisation.

The star is unpolarised, it goes away,

and all that's left over is what is around the star.

So by this technique of polarisation,

using fact that light travels

different directions, you're able to, in effect,

eliminate the starlight and you're just left with this dusty disc.

The ultimate goal, particularly of this machine,

is that we can do this with exoplanets.

Like a piece of dust around a star, an exoplanet also scatters light

and polarises light, and so, with this one,

we hope that, in the end, we'll get a spectrum of an exoplanet.

That's a magnificent ambition.

Not only are you looking at the beginnings of new solar systems,

-you're hoping to image the ones that already exist.

-Yes.

If that doesn't deserve a clear night, I don't know what does.

-Thank you very much.

-Thank you, Paul.

It's great to see the William Herschel Telescope

still hard at work,

revealing new and exciting aspects of our universe.

It's night on the mountain, it's time to go comet-hunting.

It's unbelievably dark here tonight,

so we're filming on the infra-red camera, which is just as well.

I don't know about you,

Pete, I can't see where you are, let alone my hand in front of my face.

I've gone.

-THEY LAUGH

-It is dark, isn't it? It's amazing.

-Where's the door?

-The door is... Oh, there it is. OK.

The Liverpool Telescope should give us a close-up view of the comets,

while the Isaac Newton Telescope will tell us what they're made of.

Together, they'll tell us something new about each of these comets.

There are loads of people in the control room tonight

cos we've got some students learning to operate the telescope.

So Alan's got plenty of help as we start our observing session.

The first task is to look at a bright star, one rather like the sun,

and check everything's working before we can go and look for our comet.

We're here in the control centre for the Liverpool Telescope.

Comet Brewington is up.

It's dark outside, and we're hoping to get our first glimpses.

Now, the telescope is in robotic mode,

so what's happening at the moment?

Well, we've had a few alerts tonight.

Humidity has gone over our limit,

so it's automatically closed itself down.

Humidity is now dropping away, so the enclosure is now opening up.

In a few minutes,

it will go into a sequence of exposures of Brewington,

so fingers crossed that we don't get

a bit of cloud spilling over the cold air again,

putting the humidity up and it closes again.

We'll see what happens.

Comet Brewington is travelling at 30 kilometres per second,

and we're having trouble keeping up.

We're not seeing the comet.

Can we up the integration time on the acquisition camera?

One of the challenges with this

is that telescopes such as the Isaac Newton

are used to tracking stars as the Earth rotates

and the sky moves over the course of the night.

But the comet is moving at a slightly different rate

against the background stars, so keeping track of that

and keeping it in just the right place

-is one of the big challenges of this kind of observation.

-Beautiful.

Fine. OK, we can go to the comet.

So the comet's first data is heading into the spectrograph.

And, Alan, we're exposing for how long?

We're exposing just for 60 seconds because it's always difficult

to estimate exactly how long you want to expose the camera

to collect the light from the comet,

so 60 seconds will give us a good idea

of how long we want to integrate

to capture as much information as possible.

So in less than a minute we should see our first data from the comet,

which will look like a lot of stripy lines, but they'll be exciting.

They'll be exciting stripy lines,

because most of them will be from the comet. Here we go.

-Ooh, stripy lines.

-Unfortunately, those are atmospheric,

but what we've got here are cometary.

Oh, the faint things. So this bright line is...?

This is the light from the central core of the comet,

the dust and gas surrounding the central, icy nucleus.

-That's the stuff you see when you take a picture.

-Kind of, yes.

That's right. But what we can see spreading either side

are these faint lines, due to the gases in the comet.

-There's a double line here.

-There's a double line there,

and I believe that is due to sodium.

Now, part of that may be from the comet,

part of it may be from the Earth's atmosphere,

which also has sodium in it, so after we observe the comet,

we'll go to a blank bit of sky nearby

and take another exposure,

which gives us a spectrum just of the Earth's atmosphere,

then when we subtract one from the other,

we're just left with light from the comet.

These spectral lines are enlightening,

but I want to know what Brewington looks like.

-Let's hope Lucie's got a picture.

-Jon, what have you got for us?

It looks like I've actually got it now,

so there we go, it's come up.

-This is Brewington?

-This is Brewington.

And what we're looking at here,

this is the extended atmosphere of the comet,

so the gas and dust that come off of the frozen lump

that is the comet itself.

Can you see any structures?

You sometimes get jets coming off the nucleus,

-which appear like structures.

-We can do some more processing on this.

-OK.

-If you do that, you end up with an image like this.

Now, if you look carefully,

you can see that the nucleus is right in there, but you can just see

these sort of wings, which are two jets coming off like that.

-So the nucleus is far too small to be picked up.

-Yes.

These are only kilometres across in size, but these jets,

-how far would they extend out for?

-Oh, millions of kilometres.

And they're coming from holes in the comet?

-So little spots.

-Vents. Like geysers...pretty much,

I would have thought, or fountains, or whatever you want to call them.

It's not the whole surface which is coming off in one layer,

-it's specific hotspots.

-And it hasn't got a tail?

-Not as such at the moment, no.

-That's disappointing you, isn't it?

It is! When I think of the comets, I think of the classic comet.

I want to see a lovely tail.

But still, this is really interesting to see,

because this is ultimately the source of the tail.

This atmosphere of the comet

is what then gets pushed back by the sunlight

and the solar winds and ends up creating this tail.

We've bagged our first comet,

but it's a long wait until Comet Lovejoy appears

at four o'clock in the morning.

We have high hopes for this comet.

In recent days, it's been very active.

So let's go for a five-minute exposure. Run 300.

So we've just started our first exposure on Comet Lovejoy.

It's 4.30 in the morning. We've had some problems with the spectrograph,

but we've successfully done what's called power cycling,

which means turning it off and on again,

and it's now working perfectly.

-How's it looking?

-It's looking good. This is an incredibly active comet.

We can see it really clearly in the acquisition camera,

where we're making sure that the light from where we're looking

and where we want to investigate the comet graph,

and now that light is being split up

into its component wavelengths or colours.

We're about halfway through the exposure.

Lovejoy is moving much faster than Brewington was across the sky,

so does that make it much more difficult to track?

It just means you have to concentrate more!

You can't take your eyes off the comet.

-Or these guys.

-Yes, yes.

Hi, guys. How are you getting on?

-There it is. This is what an observer would see.

-There it is!

Look at that little plasma tail. Isn't that beautiful?

And completely different to what we had before, with Brewington.

This one is much more impressive. This is what I was hoping to see!

We've only got a few seconds left before the data hits us.

-Come on.

-Oh!

Wow. It's certainly brighter than the other one.

You can see now all these C2 molecules here, C2 molecules there.

You can see it's broader as well.

This is all emission from the coma as well as the nucleus.

That's right, and then down here, we've got cyanogen. This is C3.

This could be CO+, known as carbon monoxide.

As we go up in this direction, towards the red,

we can start seeing the oxygen emission up here.

We can also start seeing possibly some H2O+ emission.

Then, of course, it's the H2O+

and the CO+, these ionised gases,

that go back to form these beautiful plasma tails,

ion tails of comets.

The spectrum of Comet Brewington's light

shows it's got hardly any molecules present.

That's what happens when the sun bakes you thousands of times.

Lovejoy, on the other hand,

is rich in water, nitrogen, carbon and oxygen.

It's younger and it's fresher

and we can also see that it's losing a lot of water -

the equivalent of ten Olympic-sized swimming pools every day.

Alan wants to see what Comet Lovejoy looks like

in the Liverpool Telescope.

-Alan, hello.

-Well timed.

-We've got the first images in. Come and have a look.

-Oh, OK.

Oh, that's beautiful, isn't it? Look at that.

That is absolutely wonderful.

Now, for Comet Brewington, we had a nice processed image

that brought out some of the structure. Have you done the same

-for this comet?

-Yes, we've got it here.

ALL EXCLAIM

That is incredible.

-Look at that tail.

-That's beautiful.

You can see that plasma tail now really nicely,

but look at that jet structure coming out of that nucleus,

and they're being pushed back by the solar wind,

possibly also by the rotation of the comet.

We're seeing some curvature there.

That could be this lawn sprinkler effect,

where the comet's rotating and so you see this spiral develop.

It's time to leave Lovejoy behind

and join the rest of the team up at the Isaac Newton Telescope

to look for Comet ISON.

It's 6am and we have an incredibly short window to find the comet.

So Comet ISON has just risen above the horizon.

I managed to get it in these binoculars.

It's a faint blob with a tail just streaking upwards,

away from the horizon, away from the sun.

But I really want to try and get it in one of these telescopes,

to get a really close-up view of it.

-Pete, how have you been getting on?

-Fantastic.

It's a fantastic comet to take a photograph of

and I'm picking up quite a bit of the tail, as well.

-Do you want to see a picture?

-I do.

-Be prepared.

-OK. You're going to wow me?

-Look at that.

You are wowing me!

Fantastic! So you can see the head there.

If I zoom in a bit, you can see some of the structure.

I wasn't expecting to see that level of structure.

But I can see one, two, three

very clear bands in that dust tail.

And the head has got a definite greenish tint to it, hasn't it?

Isn't that gorgeous?

OK, so we've got the comet for the first time

in this 12-inch telescope,

and it really is an impressive sight.

The greenish colour, very, very vivid, and the structure,

the tail extends well beyond the field of view

of the eyepiece, actually.

It's really quite a remarkable sight.

-Pete, would you like to look?

-Yeah, I'd love to.

-Condescend to look through an eyepiece?

-I'll try my best.

Remember how to use them?

-Let's have a look. Oh, wow, that's beautiful.

-Stunning, isn't it?

Look at that. I can see green in there.

How does this compare with your image over there?

Well, the image is showing some structure

and there's some structure in here.

I can see some type of sweepback in the coma.

What a corker!

It's a corker! It's a good 'un, isn't it?

-I'll go back to my camera now.

-Yeah, go on.

-It really is lovely in a telescope.

-It IS nice, isn't it?

I think what impresses me is...

The shape of it, it really looks like the material is being pushed away

from the sun. It's got this beautiful round top to it.

It's great to have seen it. This is fabulous.

A new day is upon us

and our special time with ISON is rapidly coming to an end.

Well, Alan, we've got Mercury rising now,

but we're starting to lose Comet ISON.

Yeah, unfortunately, the dawn is rising fast.

And, of course, it's getting so close to the sun.

As we stand here, it's now officially

less than one week before perihelion,

its closest point to the sun.

And so it really is diving down there into the twilight sky

and it's getting so hard to see now.

But it's a glorious sight still, even now.

It really has been a special time here.

And this sunrise is the perfect end to a long night of observing.

The horizon is a wonderfully warm orange.

But, unfortunately, it's goodbye to Comet ISON.

In the past few days,

it's been our spacecraft that have been watching Comet ISON

and in this image, with the sun blocked out,

you can see comet ISON plunging towards our star.

It's been torn apart by immense tidal forces

and this is all that remains of the kilometre-wide nucleus

after its hellish encounter.

It's certainly not the comet it once was,

but anyone with a small telescope should still go out and try

and find ISON in the predawn sky.

You can visit...

..for Pete's chart, showing you how to find it.

You can also see Lucie making a kitchen comet.

We've had a fantastic time here on La Palma,

and it's been an incredibly successful trip.

We bagged every single one of those comets that we came out to see.

We'll be taking a break as we head into the new year,

but the programme will be back in February.

From all of us here at The Sky At Night team...

BOTH: Good night.

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