0:00:31 > 0:00:33This month, we've travelled to
0:00:33 > 0:00:35one of the best observing sites
0:00:35 > 0:00:37in the world. We're on La Palma in the Canary Islands.
0:00:37 > 0:00:41We're here to chase comets and in particular Comet ISON,
0:00:41 > 0:00:43which has been getting a lot of attention
0:00:43 > 0:00:45because it might be really spectacular
0:00:45 > 0:00:49as it slingshots around the sun in just a few days' time.
0:00:49 > 0:00:52And that's not all. There are two other comets that are bright
0:00:52 > 0:00:55in our night sky at the moment, and we'll be using these telescopes
0:00:55 > 0:00:59to track down these enigmatic explorers of the solar system.
0:00:59 > 0:01:03But first, here's Pete Lawrence with his guide to what else can be seen
0:01:03 > 0:01:05in December's night sky.
0:01:11 > 0:01:14The magnificent constellation of Orion is prominent this month,
0:01:14 > 0:01:16best seen around midnight
0:01:16 > 0:01:18at the start and end of December
0:01:18 > 0:01:19when the bright moon is
0:01:19 > 0:01:20out of the way.
0:01:20 > 0:01:22The three stars that form his belt
0:01:22 > 0:01:25are very distinctive, and from them,
0:01:25 > 0:01:28his fainter sword can be seen hanging.
0:01:28 > 0:01:31Look at this with a pair of binoculars or small telescope
0:01:31 > 0:01:34and right in the middle, you'll find the Orion Nebula,
0:01:34 > 0:01:36Messier 42.
0:01:36 > 0:01:38This is a huge cloud of glowing gas,
0:01:38 > 0:01:41a place where new stars are being formed.
0:01:41 > 0:01:44Follow the belt down and left
0:01:44 > 0:01:48to locate the brightest night-time star of them all, Sirius.
0:01:48 > 0:01:50Above and slightly left of Sirius
0:01:50 > 0:01:52lies Procyon,
0:01:52 > 0:01:55a bright star in an area of sky bereft of much else.
0:01:55 > 0:01:57Draw an imaginary line
0:01:57 > 0:02:00from orange Betelgeuse in the top left of Orion
0:02:00 > 0:02:02to Sirius, on to Procyon
0:02:02 > 0:02:04and back to Betelgeuse again
0:02:04 > 0:02:06to form the Winter Triangle.
0:02:06 > 0:02:09The charts to find everything mentioned here
0:02:09 > 0:02:13can be found on our website.
0:02:18 > 0:02:22The Sky At Night has come comet-chasing
0:02:22 > 0:02:26to the volcanic island of La Palma in the Canary Islands.
0:02:26 > 0:02:28It's a week until Comet ISON
0:02:28 > 0:02:31has its close encounter with the sun.
0:02:31 > 0:02:35The volcano dominates everything and at 8,000 feet,
0:02:35 > 0:02:40the astronomical observatories sit well above the cloud layer.
0:02:40 > 0:02:44The Roque de los Muchachos, or Rock of the Boys,
0:02:44 > 0:02:47is named for these volcanic remnants up at the top.
0:02:47 > 0:02:52The Sky At Night team have joined us, and we've got a special guest,
0:02:52 > 0:02:56Alan Fitzsimmons, from the Queen's University, Belfast,
0:02:56 > 0:02:58a world expert on comets.
0:02:58 > 0:03:01From up here, you can see why astronomers have been coming
0:03:01 > 0:03:04to this site for decades. The clouds are far below us,
0:03:04 > 0:03:07there's a beautiful dark blue sky above us and we've been given
0:03:07 > 0:03:12the run of not one but two telescopes to go comet-hunting this evening.
0:03:13 > 0:03:16Comets are the primeval relics of the solar system.
0:03:16 > 0:03:20They're the leftovers from when the planets were formed.
0:03:20 > 0:03:24These pristine bits of four-billion-year-old ice and dirt
0:03:24 > 0:03:29also have complex molecules, such as alcohol, cyanide and ammonia.
0:03:30 > 0:03:36Our special comet is called C/2012 S1 ISON,
0:03:36 > 0:03:39named after the telescope team that discovered it last year.
0:03:39 > 0:03:43ISON has come from the very outer regions of the solar system,
0:03:43 > 0:03:45from a place called the Oort cloud.
0:03:46 > 0:03:50It's passed by Earth and is on a slingshot around the sun,
0:03:50 > 0:03:53getting within one million kilometres of the sun's surface
0:03:53 > 0:03:57before being flung back into outer space.
0:03:58 > 0:04:01Alan has been looking forward to seeing Comet ISON
0:04:01 > 0:04:03since it was first spotted last year.
0:04:03 > 0:04:05There's two aspects to ISON
0:04:05 > 0:04:08that make it a really special comet.
0:04:08 > 0:04:11The first is that it's its first time in from the Oort cloud.
0:04:11 > 0:04:14It's spent 4.5 billion years, as far as we know,
0:04:14 > 0:04:16out there in the depth of space,
0:04:16 > 0:04:18almost, effectively, interstellar space,
0:04:18 > 0:04:21and it's coming in for the first time.
0:04:21 > 0:04:23Now, we see many comets each year
0:04:23 > 0:04:27that are coming in from the Oort cloud, probably for the first time.
0:04:27 > 0:04:32However, Comet ISON is also going to pass very, very close to the sun.
0:04:32 > 0:04:34It's a sungrazer.
0:04:34 > 0:04:39And we've never had that combination of features
0:04:39 > 0:04:41for a comet in modern history.
0:04:41 > 0:04:45And so, right now, as it approaches the sun,
0:04:45 > 0:04:48Comet ISON doesn't know what's in store for it.
0:04:48 > 0:04:51It's just behaving like a normal comet would the first time
0:04:51 > 0:04:53it comes in from the Oort cloud.
0:04:53 > 0:04:56But as we stand here, in just over a week's time,
0:04:56 > 0:05:01it's going to be under the full force of the sun's heat.
0:05:01 > 0:05:05That's 1.7 solar radii from the surface of the sun itself
0:05:05 > 0:05:06and that, we hope,
0:05:06 > 0:05:10will reveal immensely interesting aspects,
0:05:10 > 0:05:15not only about the make-up of comets but how they're put together.
0:05:15 > 0:05:19Comet ISON is too near to the horizon for the big telescopes
0:05:19 > 0:05:21to look at, but we're incredibly lucky
0:05:21 > 0:05:25because there are a host of other bright comets we can choose from.
0:05:25 > 0:05:29It's a very special time for comets.
0:05:29 > 0:05:31We have ISON itself, of course,
0:05:31 > 0:05:33but we also have Comet Brewington,
0:05:33 > 0:05:35which is a short period comet, going around the sun.
0:05:35 > 0:05:38It only orbits the sun once every 10.8 years.
0:05:38 > 0:05:42Then we have Comet Lovejoy, which is the brightest comet in the sky
0:05:42 > 0:05:44as we stand here on La Palma,
0:05:44 > 0:05:46and it's actually really, really nice.
0:05:46 > 0:05:47It's quite high up in the sky,
0:05:47 > 0:05:49in the early morning sky,
0:05:49 > 0:05:51and it's something we can easily observe.
0:05:53 > 0:05:56With brilliantly clear skies up above La Palma, we're planning to
0:05:56 > 0:06:00make the best of them and that means we've got a long night ahead of us.
0:06:00 > 0:06:03We're going to start the evening by looking for Comet Brewington,
0:06:03 > 0:06:05just after sunset.
0:06:05 > 0:06:09Then, around 4am, we'll look for Comet Lovejoy,
0:06:09 > 0:06:13before we finish with Comet ISON just before dawn.
0:06:13 > 0:06:16It's a busy schedule and it's rather ambitious
0:06:16 > 0:06:19and so we're going to split up into two teams.
0:06:19 > 0:06:22Should make for some healthy competition.
0:06:22 > 0:06:24Well, this is our telescope for tonight.
0:06:24 > 0:06:27- This is the Liverpool Telescope. - And we're ready for it, aren't we?
0:06:27 > 0:06:29Bring on those comets.
0:06:30 > 0:06:34Chris and I have been given the keys to the Isaac Newton Telescope,
0:06:34 > 0:06:37one of the most venerable of the British telescopes on the island.
0:06:37 > 0:06:40And while it might not be as modern as some of the other telescopes
0:06:40 > 0:06:43here on La Palma, tonight we've been given use of a scientific
0:06:43 > 0:06:45secret weapon...a spectrograph.
0:06:47 > 0:06:50This is real science, and Alan is going to help us understand
0:06:50 > 0:06:52and interpret our results.
0:06:54 > 0:06:56Pete and I are looking forward to the challenge
0:06:56 > 0:06:58of imaging our two comets.
0:06:58 > 0:07:00The Liverpool Telescope
0:07:00 > 0:07:04is the largest fully robotic telescope in the world.
0:07:04 > 0:07:07Everything is pre-planned, and professionals, schools
0:07:07 > 0:07:10and amateur astronomers can use it.
0:07:10 > 0:07:12Mike Bode is the telescope director.
0:07:12 > 0:07:14- Hi, Mike.- Hello, Mike, great to see you.
0:07:14 > 0:07:16- Welcome to the Liverpool Telescope. - Thank you very much.
0:07:16 > 0:07:19A comet-hunting group recently imaged ISON with
0:07:19 > 0:07:22the Liverpool Telescope.
0:07:22 > 0:07:24Now, Mike, this is a robotic telescope.
0:07:24 > 0:07:27So, how does this one differ to the other ones on the island?
0:07:27 > 0:07:30Our philosophy of operating this telescope is like
0:07:30 > 0:07:31a space probe on the ground.
0:07:31 > 0:07:35So, during the night, there's nobody looking after it, there's nobody
0:07:35 > 0:07:38interfering with the schedule, and so on, it's all automated.
0:07:38 > 0:07:40So it's got a whole list
0:07:40 > 0:07:45of objects in its scheduler that are important to do scientifically
0:07:45 > 0:07:48or as part of the programme we do for schools, and it picks them
0:07:48 > 0:07:50at the optimum one to observe next.
0:07:50 > 0:07:53But we've plumbed in a few observations
0:07:53 > 0:07:55especially for you that are going to be done towards
0:07:55 > 0:07:58the beginning of the night when we'd normally be doing
0:07:58 > 0:08:01some calibration things, while it's still twilight.
0:08:04 > 0:08:07Alan, Chris and I are using the Isaac Newton Telescope,
0:08:07 > 0:08:10which started work on La Palma in 1984.
0:08:10 > 0:08:13In telescope terms, it's well into its middle age
0:08:13 > 0:08:16but it's still hard at work.
0:08:16 > 0:08:19- Here we go, look at it. - This is more like it.
0:08:19 > 0:08:22It's a beautiful, beautiful telescope.
0:08:22 > 0:08:26The two comets we're looking at have significant differences.
0:08:26 > 0:08:30Comet Brewington takes 10.8 years for an orbit, and it's been making
0:08:30 > 0:08:35regular trips to the inner solar system for over 100,000 years.
0:08:35 > 0:08:38It's been heated up many, many times.
0:08:39 > 0:08:43Comet Lovejoy takes around 10,000 years to go around the sun
0:08:43 > 0:08:46and so it's only been round a handful of times.
0:08:46 > 0:08:49It's younger, and it should be fresher.
0:08:49 > 0:08:52They both share the characteristic look of a comet,
0:08:52 > 0:08:57with a head or a nucleus, and a tail that streams off into the distance.
0:08:57 > 0:09:00So, the nucleus is the frozen, dirty stone ball.
0:09:00 > 0:09:03Icy dirt ball, depending on your point of view,
0:09:03 > 0:09:06that's been out there, frozen in deep space, either in
0:09:06 > 0:09:10the Kuiper belt or the Oort cloud for 4.5 billion years.
0:09:10 > 0:09:13And as it's warmed by the sun, as it approaches the sun,
0:09:13 > 0:09:17the surface ices evaporate or, rather, we say they sublimate
0:09:17 > 0:09:21because they turn directly from a solid into a gas.
0:09:21 > 0:09:24And that streams outwards from this actually relatively tiny nucleus.
0:09:24 > 0:09:28Most of the nuclei of comets are only a few kilometres across.
0:09:28 > 0:09:31Smaller than the island that we're standing on!
0:09:31 > 0:09:35But when those gases expand outwards, they form these
0:09:35 > 0:09:37temporary atmospheres that are much, much larger than
0:09:37 > 0:09:40the Earth...approaching the size of the sun.
0:09:40 > 0:09:45By studying that released atmosphere around the comet, we actually
0:09:45 > 0:09:48figure out what's buried in the really invisible
0:09:48 > 0:09:49nucleus in the centre.
0:09:52 > 0:09:54Some students are here to help us
0:09:54 > 0:09:58and to get invaluable experience at chasing comets.
0:09:58 > 0:10:02It's not an easy task while they're speeding around the sun.
0:10:02 > 0:10:05The spectrograph the students are preparing will measure
0:10:05 > 0:10:07the reflected light from the comet,
0:10:07 > 0:10:11as well as the light from the gases in its coma.
0:10:11 > 0:10:13The instrument masks off most of the comet,
0:10:13 > 0:10:19leaving a narrow slit of light, which is then spread out into a spectrum.
0:10:19 > 0:10:23Every type of gas has a different spectral fingerprint, and we can
0:10:23 > 0:10:26use that to identify the gases in the atmosphere of the comet.
0:10:26 > 0:10:30And that's something that this study of comets really tells us,
0:10:30 > 0:10:34because these are the leftovers of the formation of the solar system,
0:10:34 > 0:10:37so whilst they're changing as they come into the sun, and giving off
0:10:37 > 0:10:40all these gases, they do let us probe what was going on
0:10:40 > 0:10:444.5 billion years ago when the planets and the comets and asteroids
0:10:44 > 0:10:48were all forming. It's a real insight into the history of the solar system.
0:10:48 > 0:10:50Absolutely. If you think about it,
0:10:50 > 0:10:53it's a primordial Rosetta Stone
0:10:53 > 0:10:56going back 4.5 billion years.
0:10:56 > 0:10:59We're seeing material that has never seen the light of day since then.
0:10:59 > 0:11:02It's been locked up inside a comet,
0:11:02 > 0:11:04and now it's been released for the first time
0:11:04 > 0:11:08and, hopefully, we'll get some really nice data on it this evening.
0:11:08 > 0:11:12The telescopes have their targets and they're ready to go,
0:11:12 > 0:11:14but while we wait for night-time,
0:11:14 > 0:11:18Paul Abel's gone to see the biggest British telescope
0:11:18 > 0:11:20here on La Palma.
0:11:23 > 0:11:25Behind me stands the William Herschel Telescope,
0:11:25 > 0:11:28which, when it was built in 1987,
0:11:28 > 0:11:31was one of the world's largest optical telescopes.
0:11:31 > 0:11:35Today, it's still at the cutting edge of research in astronomy.
0:11:35 > 0:11:38Patrick Moore and The Sky At Night
0:11:38 > 0:11:42followed the astronomical progress on La Palma,
0:11:42 > 0:11:45especially the building of the William Herschel Telescope
0:11:45 > 0:11:47in the late 1980s.
0:11:47 > 0:11:49When you're building a big telescope,
0:11:49 > 0:11:52I suppose about 50% of the problems are engineering,
0:11:52 > 0:11:54and the other 50% are optical,
0:11:54 > 0:11:57and obviously, the main component, optically,
0:11:57 > 0:11:59is the big mirror of the telescope.
0:11:59 > 0:12:01Now, this mirror is 165 inches,
0:12:01 > 0:12:04or 4.2 metres, in diameter,
0:12:04 > 0:12:06and it weighs 16.4 tonnes.
0:12:06 > 0:12:09There are only two telescope mirrors larger than that -
0:12:09 > 0:12:11the Russian 236-inch,
0:12:11 > 0:12:14which, frankly, isn't very good,
0:12:14 > 0:12:18and the Panama 200-inch, which is now 40 years old.
0:12:18 > 0:12:21Now, the mirror itself has got to be amazingly accurate.
0:12:21 > 0:12:26We are talking about accuracy to something like 1/40th of a micron.
0:12:26 > 0:12:29And you can imagine how difficult that is.
0:12:29 > 0:12:31And, believe me, this mirror is going to tell us
0:12:31 > 0:12:35a great deal about the universe that we don't know at the present time.
0:12:35 > 0:12:39The William Hershel Telescope lived up to that promise.
0:12:39 > 0:12:43It revealed many insights into the expansion of the universe
0:12:43 > 0:12:46and observed the first optical gamma ray burst.
0:12:46 > 0:12:50Today, it is still at the forefront of research.
0:12:50 > 0:12:53Exoplanets are the new holy grail for astronomers,
0:12:53 > 0:12:55and a team using the telescope
0:12:55 > 0:12:59have developed a new and novel way to find them.
0:12:59 > 0:13:03Tonight, the team of astronomers in the telescope will be using
0:13:03 > 0:13:07a technique called polarisation. By using a filter like this,
0:13:07 > 0:13:10they will be able to remove the starlight
0:13:10 > 0:13:14and examine the dusty disc which circles the star.
0:13:16 > 0:13:20The team using the telescope is led by Christoph Keller
0:13:20 > 0:13:23from Leiden University in the Netherlands.
0:13:23 > 0:13:25We'll go in through here.
0:13:25 > 0:13:27You come after me. OK?
0:13:27 > 0:13:30Ah! A secret, magical door.
0:13:30 > 0:13:32Brilliant!
0:13:32 > 0:13:34Ah...yes.
0:13:36 > 0:13:39- Here we go. After you. - Thank you, thank you.
0:13:39 > 0:13:43Oh, this IS impressive. It looks like a giant Meccano set.
0:13:43 > 0:13:46Here we are.
0:13:46 > 0:13:49The idea here was to take commercial components and put them together
0:13:49 > 0:13:51in ways that nobody had done before.
0:13:51 > 0:13:54It's cheap, it's relatively fast,
0:13:54 > 0:13:58but it requires us to build this up from scratch every time.
0:13:58 > 0:14:01Perhaps you could explain, then - we have a light from a star
0:14:01 > 0:14:03with a dusty disc around.
0:14:03 > 0:14:06How are you going to take away that starlight
0:14:06 > 0:14:08so that we just end up with the disc?
0:14:08 > 0:14:11When you have light coming from a star, it's unpolarised.
0:14:11 > 0:14:14- There is no preferred direction in which the light goes.- Mm-hm.
0:14:14 > 0:14:19When you have dust or a planet or something else around the star,
0:14:19 > 0:14:21then the light from the star
0:14:21 > 0:14:25- reflects off this material and then comes to us.- I see.
0:14:25 > 0:14:29- And physics tells us that the light gets polarised.- Right.
0:14:29 > 0:14:32So what we measure is the polarisation.
0:14:32 > 0:14:35The star is unpolarised, it goes away,
0:14:35 > 0:14:38and all that's left over is what is around the star.
0:14:38 > 0:14:40So by this technique of polarisation,
0:14:40 > 0:14:41using fact that light travels
0:14:41 > 0:14:44different directions, you're able to, in effect,
0:14:44 > 0:14:47eliminate the starlight and you're just left with this dusty disc.
0:14:47 > 0:14:50The ultimate goal, particularly of this machine,
0:14:50 > 0:14:52is that we can do this with exoplanets.
0:14:52 > 0:14:56Like a piece of dust around a star, an exoplanet also scatters light
0:14:56 > 0:14:58and polarises light, and so, with this one,
0:14:58 > 0:15:01we hope that, in the end, we'll get a spectrum of an exoplanet.
0:15:01 > 0:15:04That's a magnificent ambition.
0:15:04 > 0:15:07Not only are you looking at the beginnings of new solar systems,
0:15:07 > 0:15:10- you're hoping to image the ones that already exist.- Yes.
0:15:10 > 0:15:13If that doesn't deserve a clear night, I don't know what does.
0:15:13 > 0:15:15- Thank you very much. - Thank you, Paul.
0:15:17 > 0:15:21It's great to see the William Herschel Telescope
0:15:21 > 0:15:22still hard at work,
0:15:22 > 0:15:26revealing new and exciting aspects of our universe.
0:15:33 > 0:15:37It's night on the mountain, it's time to go comet-hunting.
0:15:44 > 0:15:47It's unbelievably dark here tonight,
0:15:47 > 0:15:49so we're filming on the infra-red camera, which is just as well.
0:15:49 > 0:15:51I don't know about you,
0:15:51 > 0:15:54Pete, I can't see where you are, let alone my hand in front of my face.
0:15:54 > 0:15:56I've gone.
0:15:56 > 0:15:59- THEY LAUGH - It is dark, isn't it? It's amazing.
0:15:59 > 0:16:02- Where's the door?- The door is... Oh, there it is. OK.
0:16:02 > 0:16:05The Liverpool Telescope should give us a close-up view of the comets,
0:16:05 > 0:16:09while the Isaac Newton Telescope will tell us what they're made of.
0:16:09 > 0:16:13Together, they'll tell us something new about each of these comets.
0:16:14 > 0:16:17There are loads of people in the control room tonight
0:16:17 > 0:16:19cos we've got some students learning to operate the telescope.
0:16:19 > 0:16:23So Alan's got plenty of help as we start our observing session.
0:16:23 > 0:16:26The first task is to look at a bright star, one rather like the sun,
0:16:26 > 0:16:30and check everything's working before we can go and look for our comet.
0:16:31 > 0:16:34We're here in the control centre for the Liverpool Telescope.
0:16:34 > 0:16:36Comet Brewington is up.
0:16:36 > 0:16:40It's dark outside, and we're hoping to get our first glimpses.
0:16:40 > 0:16:41Now, the telescope is in robotic mode,
0:16:41 > 0:16:43so what's happening at the moment?
0:16:43 > 0:16:45Well, we've had a few alerts tonight.
0:16:45 > 0:16:48Humidity has gone over our limit,
0:16:48 > 0:16:50so it's automatically closed itself down.
0:16:50 > 0:16:54Humidity is now dropping away, so the enclosure is now opening up.
0:16:54 > 0:16:56In a few minutes,
0:16:56 > 0:16:59it will go into a sequence of exposures of Brewington,
0:16:59 > 0:17:01so fingers crossed that we don't get
0:17:01 > 0:17:03a bit of cloud spilling over the cold air again,
0:17:03 > 0:17:05putting the humidity up and it closes again.
0:17:05 > 0:17:08We'll see what happens.
0:17:08 > 0:17:11Comet Brewington is travelling at 30 kilometres per second,
0:17:11 > 0:17:14and we're having trouble keeping up.
0:17:14 > 0:17:16We're not seeing the comet.
0:17:16 > 0:17:20Can we up the integration time on the acquisition camera?
0:17:20 > 0:17:21One of the challenges with this
0:17:21 > 0:17:23is that telescopes such as the Isaac Newton
0:17:23 > 0:17:26are used to tracking stars as the Earth rotates
0:17:26 > 0:17:28and the sky moves over the course of the night.
0:17:28 > 0:17:31But the comet is moving at a slightly different rate
0:17:31 > 0:17:33against the background stars, so keeping track of that
0:17:33 > 0:17:35and keeping it in just the right place
0:17:35 > 0:17:39- is one of the big challenges of this kind of observation.- Beautiful.
0:17:39 > 0:17:41Fine. OK, we can go to the comet.
0:17:43 > 0:17:46So the comet's first data is heading into the spectrograph.
0:17:46 > 0:17:49And, Alan, we're exposing for how long?
0:17:49 > 0:17:53We're exposing just for 60 seconds because it's always difficult
0:17:53 > 0:17:56to estimate exactly how long you want to expose the camera
0:17:56 > 0:17:58to collect the light from the comet,
0:17:58 > 0:18:01so 60 seconds will give us a good idea
0:18:01 > 0:18:03of how long we want to integrate
0:18:03 > 0:18:05to capture as much information as possible.
0:18:05 > 0:18:08So in less than a minute we should see our first data from the comet,
0:18:08 > 0:18:12which will look like a lot of stripy lines, but they'll be exciting.
0:18:12 > 0:18:13They'll be exciting stripy lines,
0:18:13 > 0:18:16because most of them will be from the comet. Here we go.
0:18:16 > 0:18:20- Ooh, stripy lines.- Unfortunately, those are atmospheric,
0:18:20 > 0:18:23but what we've got here are cometary.
0:18:23 > 0:18:26Oh, the faint things. So this bright line is...?
0:18:26 > 0:18:30This is the light from the central core of the comet,
0:18:30 > 0:18:34the dust and gas surrounding the central, icy nucleus.
0:18:34 > 0:18:37- That's the stuff you see when you take a picture.- Kind of, yes.
0:18:37 > 0:18:40That's right. But what we can see spreading either side
0:18:40 > 0:18:43are these faint lines, due to the gases in the comet.
0:18:43 > 0:18:46- There's a double line here. - There's a double line there,
0:18:46 > 0:18:48and I believe that is due to sodium.
0:18:48 > 0:18:50Now, part of that may be from the comet,
0:18:50 > 0:18:53part of it may be from the Earth's atmosphere,
0:18:53 > 0:18:56which also has sodium in it, so after we observe the comet,
0:18:56 > 0:18:59we'll go to a blank bit of sky nearby
0:18:59 > 0:19:01and take another exposure,
0:19:01 > 0:19:04which gives us a spectrum just of the Earth's atmosphere,
0:19:04 > 0:19:06then when we subtract one from the other,
0:19:06 > 0:19:08we're just left with light from the comet.
0:19:08 > 0:19:11These spectral lines are enlightening,
0:19:11 > 0:19:14but I want to know what Brewington looks like.
0:19:14 > 0:19:17- Let's hope Lucie's got a picture. - Jon, what have you got for us?
0:19:17 > 0:19:19It looks like I've actually got it now,
0:19:19 > 0:19:21so there we go, it's come up.
0:19:21 > 0:19:23- This is Brewington? - This is Brewington.
0:19:23 > 0:19:25And what we're looking at here,
0:19:25 > 0:19:28this is the extended atmosphere of the comet,
0:19:28 > 0:19:31so the gas and dust that come off of the frozen lump
0:19:31 > 0:19:33that is the comet itself.
0:19:33 > 0:19:34Can you see any structures?
0:19:34 > 0:19:37You sometimes get jets coming off the nucleus,
0:19:37 > 0:19:40- which appear like structures.- We can do some more processing on this.
0:19:40 > 0:19:44- OK.- If you do that, you end up with an image like this.
0:19:44 > 0:19:45Now, if you look carefully,
0:19:45 > 0:19:49you can see that the nucleus is right in there, but you can just see
0:19:49 > 0:19:53these sort of wings, which are two jets coming off like that.
0:19:53 > 0:19:56- So the nucleus is far too small to be picked up.- Yes.
0:19:56 > 0:20:00These are only kilometres across in size, but these jets,
0:20:00 > 0:20:03- how far would they extend out for? - Oh, millions of kilometres.
0:20:03 > 0:20:06And they're coming from holes in the comet?
0:20:06 > 0:20:08- So little spots.- Vents. Like geysers...pretty much,
0:20:08 > 0:20:12I would have thought, or fountains, or whatever you want to call them.
0:20:12 > 0:20:15It's not the whole surface which is coming off in one layer,
0:20:15 > 0:20:19- it's specific hotspots. - And it hasn't got a tail?
0:20:19 > 0:20:23- Not as such at the moment, no. - That's disappointing you, isn't it?
0:20:23 > 0:20:27It is! When I think of the comets, I think of the classic comet.
0:20:27 > 0:20:28I want to see a lovely tail.
0:20:28 > 0:20:31But still, this is really interesting to see,
0:20:31 > 0:20:34because this is ultimately the source of the tail.
0:20:34 > 0:20:35This atmosphere of the comet
0:20:35 > 0:20:38is what then gets pushed back by the sunlight
0:20:38 > 0:20:42and the solar winds and ends up creating this tail.
0:20:45 > 0:20:47We've bagged our first comet,
0:20:47 > 0:20:50but it's a long wait until Comet Lovejoy appears
0:20:50 > 0:20:52at four o'clock in the morning.
0:20:52 > 0:20:54We have high hopes for this comet.
0:20:54 > 0:20:57In recent days, it's been very active.
0:21:06 > 0:21:10So let's go for a five-minute exposure. Run 300.
0:21:10 > 0:21:14So we've just started our first exposure on Comet Lovejoy.
0:21:14 > 0:21:17It's 4.30 in the morning. We've had some problems with the spectrograph,
0:21:17 > 0:21:20but we've successfully done what's called power cycling,
0:21:20 > 0:21:22which means turning it off and on again,
0:21:22 > 0:21:23and it's now working perfectly.
0:21:23 > 0:21:27- How's it looking?- It's looking good. This is an incredibly active comet.
0:21:27 > 0:21:31We can see it really clearly in the acquisition camera,
0:21:31 > 0:21:34where we're making sure that the light from where we're looking
0:21:34 > 0:21:36and where we want to investigate the comet graph,
0:21:36 > 0:21:38and now that light is being split up
0:21:38 > 0:21:40into its component wavelengths or colours.
0:21:40 > 0:21:43We're about halfway through the exposure.
0:21:43 > 0:21:46Lovejoy is moving much faster than Brewington was across the sky,
0:21:46 > 0:21:50so does that make it much more difficult to track?
0:21:50 > 0:21:52It just means you have to concentrate more!
0:21:52 > 0:21:55You can't take your eyes off the comet.
0:21:55 > 0:21:57- Or these guys.- Yes, yes.
0:21:59 > 0:22:03Hi, guys. How are you getting on?
0:22:03 > 0:22:07- There it is. This is what an observer would see.- There it is!
0:22:07 > 0:22:13Look at that little plasma tail. Isn't that beautiful?
0:22:13 > 0:22:16And completely different to what we had before, with Brewington.
0:22:16 > 0:22:21This one is much more impressive. This is what I was hoping to see!
0:22:21 > 0:22:24We've only got a few seconds left before the data hits us.
0:22:27 > 0:22:29- Come on.- Oh!
0:22:29 > 0:22:33Wow. It's certainly brighter than the other one.
0:22:33 > 0:22:39You can see now all these C2 molecules here, C2 molecules there.
0:22:39 > 0:22:41You can see it's broader as well.
0:22:41 > 0:22:44This is all emission from the coma as well as the nucleus.
0:22:44 > 0:22:49That's right, and then down here, we've got cyanogen. This is C3.
0:22:49 > 0:22:53This could be CO+, known as carbon monoxide.
0:22:53 > 0:22:56As we go up in this direction, towards the red,
0:22:56 > 0:22:59we can start seeing the oxygen emission up here.
0:22:59 > 0:23:02We can also start seeing possibly some H2O+ emission.
0:23:02 > 0:23:04Then, of course, it's the H2O+
0:23:04 > 0:23:08and the CO+, these ionised gases,
0:23:08 > 0:23:10that go back to form these beautiful plasma tails,
0:23:10 > 0:23:12ion tails of comets.
0:23:13 > 0:23:16The spectrum of Comet Brewington's light
0:23:16 > 0:23:19shows it's got hardly any molecules present.
0:23:19 > 0:23:23That's what happens when the sun bakes you thousands of times.
0:23:23 > 0:23:25Lovejoy, on the other hand,
0:23:25 > 0:23:28is rich in water, nitrogen, carbon and oxygen.
0:23:28 > 0:23:30It's younger and it's fresher
0:23:30 > 0:23:33and we can also see that it's losing a lot of water -
0:23:33 > 0:23:38the equivalent of ten Olympic-sized swimming pools every day.
0:23:40 > 0:23:43Alan wants to see what Comet Lovejoy looks like
0:23:43 > 0:23:45in the Liverpool Telescope.
0:23:45 > 0:23:48- Alan, hello.- Well timed.
0:23:48 > 0:23:51- We've got the first images in. Come and have a look.- Oh, OK.
0:23:51 > 0:23:54Oh, that's beautiful, isn't it? Look at that.
0:23:54 > 0:23:56That is absolutely wonderful.
0:23:56 > 0:23:59Now, for Comet Brewington, we had a nice processed image
0:23:59 > 0:24:02that brought out some of the structure. Have you done the same
0:24:02 > 0:24:04- for this comet? - Yes, we've got it here.
0:24:04 > 0:24:06ALL EXCLAIM
0:24:06 > 0:24:08That is incredible.
0:24:08 > 0:24:10- Look at that tail.- That's beautiful.
0:24:10 > 0:24:13You can see that plasma tail now really nicely,
0:24:13 > 0:24:16but look at that jet structure coming out of that nucleus,
0:24:16 > 0:24:19and they're being pushed back by the solar wind,
0:24:19 > 0:24:21possibly also by the rotation of the comet.
0:24:21 > 0:24:23We're seeing some curvature there.
0:24:23 > 0:24:26That could be this lawn sprinkler effect,
0:24:26 > 0:24:29where the comet's rotating and so you see this spiral develop.
0:24:32 > 0:24:35It's time to leave Lovejoy behind
0:24:35 > 0:24:39and join the rest of the team up at the Isaac Newton Telescope
0:24:39 > 0:24:41to look for Comet ISON.
0:24:43 > 0:24:48It's 6am and we have an incredibly short window to find the comet.
0:24:50 > 0:24:53So Comet ISON has just risen above the horizon.
0:24:53 > 0:24:55I managed to get it in these binoculars.
0:24:55 > 0:24:57It's a faint blob with a tail just streaking upwards,
0:24:57 > 0:25:00away from the horizon, away from the sun.
0:25:00 > 0:25:02But I really want to try and get it in one of these telescopes,
0:25:02 > 0:25:05to get a really close-up view of it.
0:25:08 > 0:25:11- Pete, how have you been getting on? - Fantastic.
0:25:11 > 0:25:13It's a fantastic comet to take a photograph of
0:25:13 > 0:25:15and I'm picking up quite a bit of the tail, as well.
0:25:15 > 0:25:17- Do you want to see a picture?- I do.
0:25:17 > 0:25:19- Be prepared.- OK. You're going to wow me?- Look at that.
0:25:19 > 0:25:21You are wowing me!
0:25:21 > 0:25:23Fantastic! So you can see the head there.
0:25:23 > 0:25:25If I zoom in a bit, you can see some of the structure.
0:25:25 > 0:25:28I wasn't expecting to see that level of structure.
0:25:28 > 0:25:29But I can see one, two, three
0:25:29 > 0:25:33very clear bands in that dust tail.
0:25:33 > 0:25:36And the head has got a definite greenish tint to it, hasn't it?
0:25:36 > 0:25:38Isn't that gorgeous?
0:25:38 > 0:25:40OK, so we've got the comet for the first time
0:25:40 > 0:25:42in this 12-inch telescope,
0:25:42 > 0:25:44and it really is an impressive sight.
0:25:44 > 0:25:48The greenish colour, very, very vivid, and the structure,
0:25:48 > 0:25:50the tail extends well beyond the field of view
0:25:50 > 0:25:52of the eyepiece, actually.
0:25:52 > 0:25:54It's really quite a remarkable sight.
0:25:54 > 0:25:56- Pete, would you like to look? - Yeah, I'd love to.
0:25:56 > 0:25:58- Condescend to look through an eyepiece?- I'll try my best.
0:25:58 > 0:26:00Remember how to use them?
0:26:00 > 0:26:03- Let's have a look. Oh, wow, that's beautiful.- Stunning, isn't it?
0:26:03 > 0:26:06Look at that. I can see green in there.
0:26:06 > 0:26:08How does this compare with your image over there?
0:26:08 > 0:26:11Well, the image is showing some structure
0:26:11 > 0:26:12and there's some structure in here.
0:26:12 > 0:26:16I can see some type of sweepback in the coma.
0:26:16 > 0:26:17What a corker!
0:26:17 > 0:26:20It's a corker! It's a good 'un, isn't it?
0:26:20 > 0:26:24- I'll go back to my camera now. - Yeah, go on.
0:26:24 > 0:26:27- It really is lovely in a telescope. - It IS nice, isn't it?
0:26:27 > 0:26:29I think what impresses me is...
0:26:29 > 0:26:33The shape of it, it really looks like the material is being pushed away
0:26:33 > 0:26:37from the sun. It's got this beautiful round top to it.
0:26:37 > 0:26:40It's great to have seen it. This is fabulous.
0:26:43 > 0:26:45A new day is upon us
0:26:45 > 0:26:50and our special time with ISON is rapidly coming to an end.
0:26:51 > 0:26:53Well, Alan, we've got Mercury rising now,
0:26:53 > 0:26:55but we're starting to lose Comet ISON.
0:26:55 > 0:26:58Yeah, unfortunately, the dawn is rising fast.
0:26:58 > 0:27:00And, of course, it's getting so close to the sun.
0:27:00 > 0:27:02As we stand here, it's now officially
0:27:02 > 0:27:04less than one week before perihelion,
0:27:04 > 0:27:06its closest point to the sun.
0:27:06 > 0:27:10And so it really is diving down there into the twilight sky
0:27:10 > 0:27:11and it's getting so hard to see now.
0:27:11 > 0:27:14But it's a glorious sight still, even now.
0:27:14 > 0:27:16It really has been a special time here.
0:27:16 > 0:27:20And this sunrise is the perfect end to a long night of observing.
0:27:20 > 0:27:24The horizon is a wonderfully warm orange.
0:27:24 > 0:27:27But, unfortunately, it's goodbye to Comet ISON.
0:27:30 > 0:27:31In the past few days,
0:27:31 > 0:27:35it's been our spacecraft that have been watching Comet ISON
0:27:35 > 0:27:38and in this image, with the sun blocked out,
0:27:38 > 0:27:42you can see comet ISON plunging towards our star.
0:27:42 > 0:27:46It's been torn apart by immense tidal forces
0:27:46 > 0:27:50and this is all that remains of the kilometre-wide nucleus
0:27:50 > 0:27:53after its hellish encounter.
0:27:53 > 0:27:56It's certainly not the comet it once was,
0:27:56 > 0:27:59but anyone with a small telescope should still go out and try
0:27:59 > 0:28:02and find ISON in the predawn sky.
0:28:02 > 0:28:04You can visit...
0:28:06 > 0:28:09..for Pete's chart, showing you how to find it.
0:28:09 > 0:28:13You can also see Lucie making a kitchen comet.
0:28:15 > 0:28:19We've had a fantastic time here on La Palma,
0:28:19 > 0:28:21and it's been an incredibly successful trip.
0:28:21 > 0:28:25We bagged every single one of those comets that we came out to see.
0:28:25 > 0:28:27We'll be taking a break as we head into the new year,
0:28:27 > 0:28:30but the programme will be back in February.
0:28:30 > 0:28:32From all of us here at The Sky At Night team...
0:28:32 > 0:28:34BOTH: Good night.
0:28:47 > 0:28:49Subtitles by Red Bee Media Ltd