0:00:07 > 0:00:11This month, we've come to the Roque de los Muchachos Observatory
0:00:11 > 0:00:14on the island of La Palma, in the Canary Islands.
0:00:18 > 0:00:21It's home to the largest collection of major telescopes
0:00:21 > 0:00:24anywhere in Europe, including this magnificent machine,
0:00:24 > 0:00:26the Gran Telescopio Canarias,
0:00:26 > 0:00:30the largest steerable optical telescope anywhere in the world.
0:00:32 > 0:00:34Over the next few nights,
0:00:34 > 0:00:36we'll be putting some of these telescopes through their paces,
0:00:36 > 0:00:41as we take a voyage of discovery out through the galaxy and beyond.
0:00:41 > 0:00:43A voyage chartered by you.
0:00:46 > 0:00:50Last month, we invited you to suggest the objects in the night sky
0:00:50 > 0:00:53that you would like to have a much closer look at.
0:00:53 > 0:00:55You sent us loads of suggestions.
0:00:57 > 0:00:59And we've chosen some of the best
0:00:59 > 0:01:02to be imaged by these powerful instruments.
0:01:04 > 0:01:08Tonight, we're taking over the telescopes of La Palma.
0:01:08 > 0:01:10Welcome to The Sky At Night.
0:01:43 > 0:01:47It's amazing. We are actually above the clouds.
0:01:47 > 0:01:50When people think of La Palma, they think of sun, sand and sea.
0:01:50 > 0:01:53But up here it's quite different.
0:01:53 > 0:01:58This site sits 2,400 metres above sea level, on a dormant volcano,
0:01:58 > 0:02:00and it's quite cold.
0:02:00 > 0:02:02But there's a big compensation.
0:02:02 > 0:02:05Viewing conditions up here are amongst the best in the world,
0:02:05 > 0:02:07and with virtually no light pollution
0:02:07 > 0:02:10and up to 300 clear nights a year,
0:02:10 > 0:02:12it's a great place to do observing.
0:02:18 > 0:02:21Because of these exceptional conditions,
0:02:21 > 0:02:24countries from all over Europe have built telescopes here.
0:02:27 > 0:02:30There are over 30 of them on the mountain,
0:02:30 > 0:02:34all designed to probe the secrets of the universe in different ways.
0:02:36 > 0:02:39The telescope behind is called MAGIC,
0:02:39 > 0:02:42and it's designed to look for gamma ray bursts in distant galaxies.
0:02:42 > 0:02:46And up there on the hill is the Swedish solar telescope,
0:02:46 > 0:02:49which is looking at our local star, the sun.
0:02:54 > 0:02:57And dotted across the hillsides,
0:02:57 > 0:03:00these large domes contain huge instruments
0:03:00 > 0:03:03which can look deep into the universe.
0:03:03 > 0:03:08These are the telescopes we'll be using to view your suggestions.
0:03:08 > 0:03:13We'll be looking at distant galaxies using the vast GTC,
0:03:13 > 0:03:15known to astronomers as GranTeCan.
0:03:17 > 0:03:20We'll be joining the hunt for exoplanets around other stars.
0:03:22 > 0:03:24And we'll be following Alan Fitzsimmons,
0:03:24 > 0:03:27as he shows us how to track down some of the smallest bodies
0:03:27 > 0:03:30in the solar system - comets and asteroids.
0:03:31 > 0:03:35But first, Chris has been trying to image some of the other objects
0:03:35 > 0:03:38you suggested we should look for in the night sky.
0:03:38 > 0:03:40This building below me houses
0:03:40 > 0:03:43one of the newer telescopes on the mountain,
0:03:43 > 0:03:44the Liverpool Telescope,
0:03:44 > 0:03:47and any minute now it will spring into action
0:03:47 > 0:03:49and begin its night's observing.
0:03:53 > 0:03:56The Liverpool Telescope has a mirror two metres across.
0:03:56 > 0:04:01But what makes it really remarkable is that it's completely robotic,
0:04:01 > 0:04:04and available to astronomers all over the world.
0:04:04 > 0:04:07The nice thing about the Liverpool Telescope is that you can control it
0:04:07 > 0:04:10from anywhere with just a web browser.
0:04:10 > 0:04:12And so tonight, we've decided
0:04:12 > 0:04:14we're going to look at the Waterfall Nebula.
0:04:14 > 0:04:17It's one of the most intriguing objects in the sky.
0:04:17 > 0:04:20It's an excellent suggestion from Lewis Ross Jones.
0:04:20 > 0:04:22Now, the nebula is in the constellation of Orion,
0:04:22 > 0:04:24it's just below the belt.
0:04:24 > 0:04:26I've already put in the coordinates,
0:04:26 > 0:04:28I've selected the filters that we're going to use
0:04:28 > 0:04:31so that we can build up a colour picture of the object.
0:04:31 > 0:04:35So, with all of that data here, I can click a button
0:04:35 > 0:04:38and that object is now in the queue for tonight's observations,
0:04:38 > 0:04:39and so at some point later on,
0:04:39 > 0:04:42the Liverpool Telescope will swing round to Orion
0:04:42 > 0:04:44and give us our images.
0:04:58 > 0:05:00It really is dark out here.
0:05:00 > 0:05:03It's one of the best skies I've ever seen.
0:05:03 > 0:05:04When I first came outside,
0:05:04 > 0:05:08I could see the Milky Way stretching all the way from the horizon,
0:05:08 > 0:05:11up through Cassiopeia, overhead and then down through Orion,
0:05:11 > 0:05:13where the Waterfall Nebula is.
0:05:13 > 0:05:16And it's particularly clear in that part of the sky right now,
0:05:16 > 0:05:19so I hope we're getting some excellent images.
0:05:29 > 0:05:32Another great advantage of a robotic telescope is that
0:05:32 > 0:05:34you don't have to stay up all night.
0:05:34 > 0:05:39You just wait for your images to be e-mailed to you the next morning.
0:05:39 > 0:05:42It's ten o'clock and we've now got the results from last night's run
0:05:42 > 0:05:44on the Liverpool Telescope,
0:05:44 > 0:05:47including our observations of the Waterfall Nebula.
0:05:47 > 0:05:49So, let's have a look and see what we've got.
0:05:49 > 0:05:51All of our images are here.
0:05:51 > 0:05:54Let's start by looking at the blue image that we took.
0:05:54 > 0:05:57In blue light, the image is pretty disappointing.
0:05:57 > 0:06:01You can only just make out the faint outline of the nebula.
0:06:02 > 0:06:04But when we look at the image taken with a filter
0:06:04 > 0:06:07that lets through light from hydrogen gas,
0:06:07 > 0:06:12we see the fine detail, and the waterfall comes to life.
0:06:12 > 0:06:14But an individual image can't tell you too much.
0:06:14 > 0:06:16What we have to do is put them together
0:06:16 > 0:06:19to create a colour composite. So let's do that.
0:06:19 > 0:06:22There we go. It's actually a beautiful image.
0:06:23 > 0:06:26It's easy to see how the structure got its name.
0:06:26 > 0:06:28There's even a splash of hot green gas
0:06:28 > 0:06:32at what appears to be the bottom of the waterfall.
0:06:33 > 0:06:35It's tempting to say there must be an object in here
0:06:35 > 0:06:40emitting a jet, which produces this stream of material,
0:06:40 > 0:06:43but we now know this isn't a waterfall at all,
0:06:43 > 0:06:47this is a shock wave travelling through space in this direction.
0:06:47 > 0:06:50To see where it comes from, we need a wider view,
0:06:50 > 0:06:53so we've got one of those. We go here.
0:06:53 > 0:06:57You can see, here's the waterfall, but it comes from this place here,
0:06:57 > 0:07:00a place where there are four young hot stars
0:07:00 > 0:07:02in orbit around each other.
0:07:02 > 0:07:04And those stars, about 30,000 years ago,
0:07:04 > 0:07:07had a catastrophic encounter that
0:07:07 > 0:07:10set off the shock, which has been travelling through space ever since.
0:07:10 > 0:07:14One of the reasons we know that is that the waterfall is here,
0:07:14 > 0:07:16but on the opposite side there's a smaller nebula,
0:07:16 > 0:07:19the counterpart to the waterfall,
0:07:19 > 0:07:22that shows the other side of the shock.
0:07:22 > 0:07:24What I really like about this story
0:07:24 > 0:07:26is that it means this region
0:07:26 > 0:07:28of space is changing.
0:07:28 > 0:07:30If we came back in a few hundred years' time, the waterfall
0:07:30 > 0:07:34will have moved and everything will look different.
0:07:36 > 0:07:39Now, from some of the grandest objects in the night sky
0:07:39 > 0:07:41to some of the smallest.
0:07:41 > 0:07:44Twitter user Tony Tiger wrote in to ask if we could try and get
0:07:44 > 0:07:47an image of a rogue asteroid.
0:07:48 > 0:07:53A rogue asteroid is one that may in the future collide with the Earth,
0:07:53 > 0:07:56with devastating consequences.
0:07:56 > 0:08:00But rocky asteroids and their icy counterparts, comets,
0:08:00 > 0:08:04are some of the hardest objects to image, because they're so small,
0:08:04 > 0:08:07dark and they move so quickly across the sky.
0:08:07 > 0:08:11We asked astronomer Alan Fitzsimmons
0:08:11 > 0:08:13who's currently observing on La Palma,
0:08:13 > 0:08:17to show us how to find these tiny but potentially deadly bodies.
0:08:19 > 0:08:23So the important thing of course is that we need to keep the camera
0:08:23 > 0:08:26as cold as possible. It won't take long to fill up,
0:08:26 > 0:08:27because it was filled up this afternoon,
0:08:27 > 0:08:30so it'll only take a couple of minutes before we get
0:08:30 > 0:08:32the liquid nitrogen shooting back out.
0:08:32 > 0:08:34This is the Isaac Newton Telescope.
0:08:34 > 0:08:37It was originally built at the Royal Greenwich Observatory
0:08:37 > 0:08:40at Herstmonceux in East Sussex in the 1960s,
0:08:40 > 0:08:45but it was re-sited to the clear skies of La Palma in the 1980s.
0:08:45 > 0:08:49The mirror of the Isaac Newton Telescope is 2.5 metres across.
0:08:49 > 0:08:51That's about 100 inches in old money.
0:08:51 > 0:08:55And it's got a field of view of half a degree across on the night sky.
0:08:55 > 0:08:57That's about the size of the full moon.
0:08:57 > 0:09:01That allows us to survey huge areas of sky at a single time,
0:09:01 > 0:09:05and look for comets, asteroids and anything else we want to observe.
0:09:08 > 0:09:10- 41.3.- 41.3.
0:09:10 > 0:09:1210 plus 5.
0:09:12 > 0:09:13- 05.- 18.- 18.
0:09:13 > 0:09:15- 45.- 45.
0:09:15 > 0:09:17J 2000.
0:09:20 > 0:09:22And we're on our way.
0:09:24 > 0:09:28So when we use telescopes like this to study comets and asteroids,
0:09:28 > 0:09:31we're not trying to see details on their surfaces.
0:09:31 > 0:09:33We can't, they're far too small.
0:09:33 > 0:09:34In fact, most of the time we're trying to do
0:09:34 > 0:09:36one of a couple of things -
0:09:36 > 0:09:40either we're trying to discover them, to find out where they are,
0:09:40 > 0:09:42or we're trying to figure out their orbits.
0:09:42 > 0:09:45If we get their orbits correct,
0:09:45 > 0:09:48we can figure out where they've come from in the past, and we can also
0:09:48 > 0:09:51hopefully figure out where they're going in the future,
0:09:51 > 0:09:54including whether or not they're going to come near our planet.
0:09:54 > 0:09:57- I'm getting responses now. - Good.
0:09:57 > 0:09:59Um... Whoa, that was a bright satellite!
0:09:59 > 0:10:02I think the Space Station's just flown over.
0:10:02 > 0:10:04I love the Space Station.
0:10:05 > 0:10:08When not looking at the Space Station,
0:10:08 > 0:10:10Alan and his colleague Matthew Knight
0:10:10 > 0:10:12will be spending the night trying to observe
0:10:12 > 0:10:15a number of asteroids and comets,
0:10:15 > 0:10:17and we're hoping they can fulfil our request
0:10:17 > 0:10:19by capturing an image of one
0:10:19 > 0:10:21that's never been observed from the Earth before.
0:10:21 > 0:10:23Let's see.
0:10:23 > 0:10:25323P has only been seen from space
0:10:25 > 0:10:29by the solar observation satellite SOHO,
0:10:29 > 0:10:32and it's unclear if it's an asteroid or a comet.
0:10:34 > 0:10:37You can see it right here, this white dot, as it goes through.
0:10:37 > 0:10:41And it passes through a little bit more than once every four years.
0:10:41 > 0:10:43We're trying to study it from the ground.
0:10:43 > 0:10:45It's never been seen from the ground before.
0:10:45 > 0:10:48And we're trying to determine if it's a comet or if it's an asteroid,
0:10:48 > 0:10:50because when it comes so close to the sun,
0:10:50 > 0:10:52more or less anything would look like a comet,
0:10:52 > 0:10:55so we're studying it here today to determine what it is.
0:10:57 > 0:10:59From current calculations,
0:10:59 > 0:11:04323P should be 50% further from the sun than the Earth is,
0:11:04 > 0:11:08located somewhere around the constellations of Cancer and Gemini.
0:11:10 > 0:11:13They're using a piece of software designed to track
0:11:13 > 0:11:15the movement of comets and asteroids.
0:11:15 > 0:11:18If they're searching the right part of the sky,
0:11:18 > 0:11:21the object should leap out of the picture
0:11:21 > 0:11:23as a single bright point of light,
0:11:23 > 0:11:27while the stars and galaxies in the background remain blurred.
0:11:29 > 0:11:32But after three nights observing, there's been no sign of it.
0:11:32 > 0:11:35And time is running out.
0:11:35 > 0:11:38- OK. Processing done. - OK, here we go, then.
0:11:38 > 0:11:40So, we'll start from the bottom, shall we?
0:11:40 > 0:11:41Yeah. Be methodical about it.
0:11:41 > 0:11:44Yeah. No, I think that's noise.
0:11:44 > 0:11:46- Yeah?- Yeah.- Yeah.
0:11:46 > 0:11:49You see...spot anything else there?
0:11:49 > 0:11:51- Nope.- No, neither do I.
0:11:51 > 0:11:53- Try zooming in.- No...
0:11:55 > 0:11:57- Doubt it.- No.- No.
0:11:58 > 0:12:02Right. OK, so the summary is, at the moment we are still looking.
0:12:02 > 0:12:04We have not found the comet.
0:12:04 > 0:12:09Erm... We did a pretty deep search of that particular survey field,
0:12:09 > 0:12:12and we're pretty sure there is nothing there.
0:12:12 > 0:12:16But that was only half a degree across the size of the full moon.
0:12:16 > 0:12:19We've got a few other fields still to process.
0:12:19 > 0:12:24It could mean that it's smaller than we expected it to be,
0:12:24 > 0:12:27it could be darker than we expected it to be,
0:12:27 > 0:12:29so it's fainter than what we expected.
0:12:29 > 0:12:33Or it could be that it's in another part of the sky
0:12:33 > 0:12:35that we just haven't checked or surveyed yet.
0:12:35 > 0:12:37So sometimes astronomy is like this.
0:12:37 > 0:12:40Sometimes you get what you want, sometimes you don't.
0:12:42 > 0:12:45But although 323P remains elusive,
0:12:45 > 0:12:49as part of their night's work, Alan and Matthew were able to capture
0:12:49 > 0:12:52an image of a rogue asteroid for us,
0:12:52 > 0:12:55albeit one that was already well known.
0:12:55 > 0:12:57Yeah, that's a beautiful image.
0:12:57 > 0:13:00There's a rogue asteroid for you.
0:13:05 > 0:13:08OK, so we were asked to image a definite asteroid.
0:13:08 > 0:13:11In fact, a rogue asteroid, one that comes close to the Earth.
0:13:11 > 0:13:15And so we've take these data of one called 1995CR,
0:13:15 > 0:13:18and in these images that I'm blinking through,
0:13:18 > 0:13:22you can see it moving against the background stars and galaxies.
0:13:22 > 0:13:24From our brightness measurements,
0:13:24 > 0:13:27we know that this is about 100 metres across,
0:13:27 > 0:13:31and we also know from its orbit that it can come within
0:13:31 > 0:13:332 million kilometres of the Earth.
0:13:33 > 0:13:37So, if it ever hit us, it could easily wipe out a city.
0:13:37 > 0:13:41Now, we know we're safe from this asteroid for the next 100 years,
0:13:41 > 0:13:44but to be sure on a longer timescale in the far future,
0:13:44 > 0:13:46we need a better orbit,
0:13:46 > 0:13:48so we needed to take more data for this asteroid,
0:13:48 > 0:13:51so thanks for the request.
0:13:53 > 0:13:54With these new observations,
0:13:54 > 0:13:58it will be possible to refine the orbit of the asteroid
0:13:58 > 0:14:01to find out whether it will endanger the Earth in the future.
0:14:01 > 0:14:03You'll be sure to hear about it if it does!
0:14:07 > 0:14:09When the Isaac Newton Telescope was built,
0:14:09 > 0:14:11its 2.5-metre mirror made it
0:14:11 > 0:14:14the fifth-largest telescope in the world.
0:14:14 > 0:14:19But since then, many much larger optical telescopes have been built,
0:14:19 > 0:14:24including the biggest of them all, the Gran Telescopio Canarias.
0:14:25 > 0:14:28Maggie has been looking into the remarkable feats of engineering
0:14:28 > 0:14:30that make this telescope possible,
0:14:30 > 0:14:35and finding out what the astronomers here at using it for.
0:14:37 > 0:14:39What we're seeing from up here
0:14:39 > 0:14:41is the world's largest telescope mirror,
0:14:41 > 0:14:44coming in at 10.4 metres.
0:14:44 > 0:14:46Now, if you look carefully, you might notice
0:14:46 > 0:14:48it's not actually a single piece of glass.
0:14:48 > 0:14:51It's actually made up of 36 hexagonal pieces which butt up
0:14:51 > 0:14:54against each other to make a continuous area
0:14:54 > 0:14:57which is roughly the size of half a tennis court.
0:14:58 > 0:15:00As it gets dark outside,
0:15:00 > 0:15:03what the astronomers do is they prepare for a night's observation.
0:15:03 > 0:15:05The first thing they do is open up the telescope dome,
0:15:05 > 0:15:09and then point the telescope to the object they want to see.
0:15:09 > 0:15:13Now, light from that object shines down onto that huge primary mirror
0:15:13 > 0:15:15and then it gets reflected up to the secondary mirror,
0:15:15 > 0:15:18which sits just here. You can't see it so well from here,
0:15:18 > 0:15:21but you can see its reflection in the primary mirror.
0:15:21 > 0:15:25Now, light is then focused down into that tube in the centre.
0:15:25 > 0:15:28That tube actually directs light to the instruments that sit either side
0:15:28 > 0:15:30of the main mirror.
0:15:30 > 0:15:32It's an amazing piece of engineering.
0:15:36 > 0:15:40To enable it to point anywhere in the sky, the whole telescope,
0:15:40 > 0:15:44all 400 tonnes of it, is mounted on a moving platform.
0:15:46 > 0:15:49I think it's amazing. The biggest telescope in the world,
0:15:49 > 0:15:52and what always surprises me is how smooth they run.
0:15:52 > 0:15:56You just don't feel any vibrations, nothing. It just glides.
0:15:57 > 0:16:01What I find fascinating about telescopes like these is,
0:16:01 > 0:16:04for all their huge mirrors and complicated optics,
0:16:04 > 0:16:06they're not much better in terms of magnification
0:16:06 > 0:16:08than your best amateur telescopes,
0:16:08 > 0:16:12but where they do gain is in terms of light-gathering power,
0:16:12 > 0:16:14because when you've got a mirror that big,
0:16:14 > 0:16:17you can see faint distant objects so, so much more clearly.
0:16:21 > 0:16:26The GTC is so sensitive it could detect a light from a single candle
0:16:26 > 0:16:29as far away as Mars.
0:16:31 > 0:16:33But what the telescope is really used for
0:16:33 > 0:16:35is looking deep into space...
0:16:37 > 0:16:41..to see objects that, although intrinsically very bright,
0:16:41 > 0:16:43are extremely far away.
0:16:47 > 0:16:49GranTeCan has kindly agreed
0:16:49 > 0:16:52to devote some of their valuable viewing time
0:16:52 > 0:16:55to capture an image especially for us.
0:16:55 > 0:17:00Many of you, Angela Southwood, Mark Williams and George Brown,
0:17:00 > 0:17:05to name but three, wrote in to ask that we image galaxies.
0:17:05 > 0:17:09Many were suggested but we had to choose just one.
0:17:11 > 0:17:16And so the giant telescope homed in on NGC891,
0:17:16 > 0:17:18a galaxy much like the Milky Way,
0:17:18 > 0:17:2230 million light years from Earth.
0:17:22 > 0:17:24So, the telescope is now pointing?
0:17:24 > 0:17:26We're now right there.
0:17:26 > 0:17:29So, are we actually getting an exposure as we speak?
0:17:29 > 0:17:30It's reading out.
0:17:30 > 0:17:32OK, so you've got the exposure.
0:17:32 > 0:17:35- Yes.- In a few seconds, we're going to see the very first image.
0:17:35 > 0:17:36It will appear.
0:17:42 > 0:17:44It's beautiful!
0:17:45 > 0:17:48At a mere 30 million light years away,
0:17:48 > 0:17:52the galaxy is too big for GranTeCan to image in a single frame.
0:17:53 > 0:17:57And it takes a range of exposures at different wavelengths of light.
0:17:59 > 0:18:02Stefan, can you tell me, what are you seeing here?
0:18:02 > 0:18:05So, basically, spiral galaxies are like various plain discs.
0:18:05 > 0:18:11For example, our Milky Way has an extension of 100,000 light years,
0:18:11 > 0:18:15that's pretty big, but it's only a few thousand light years thick.
0:18:15 > 0:18:19So, it basically has the form of a Frisbee, or a pizza,
0:18:19 > 0:18:21or whatever you like.
0:18:21 > 0:18:24And the particular thing about this galaxy is that we are looking at it
0:18:24 > 0:18:26right from the side.
0:18:26 > 0:18:30All the light you see here comes from many billions of stars.
0:18:30 > 0:18:34- That make up the galaxy.- A galaxy like this consists of
0:18:34 > 0:18:37at least 100 billion stars.
0:18:37 > 0:18:41- Similar to our own.- So, we do not see any single star in that galaxy.
0:18:41 > 0:18:45At fast first glance, you may think that there are no stars,
0:18:45 > 0:18:47where you see the black stripes,
0:18:47 > 0:18:49but there are as many stars
0:18:49 > 0:18:51as in all the other regions,
0:18:51 > 0:18:56it's just that the light is blocked by the dust in the foreground.
0:18:56 > 0:19:00Those are the details we can make out on the first view,
0:19:00 > 0:19:02but to get the best image of the galaxy,
0:19:02 > 0:19:06we needed to process all the images we took that night
0:19:06 > 0:19:08into a single composite.
0:19:10 > 0:19:13This is the finished image.
0:19:15 > 0:19:18A stunning view of galaxy NGC891,
0:19:18 > 0:19:22taken by the Gran Telescopio Canarias.
0:19:29 > 0:19:32Now, not everything that you requested we look at
0:19:32 > 0:19:34requires a huge professional telescope.
0:19:34 > 0:19:38One of the most popular suggestions we had was to look at the moon,
0:19:38 > 0:19:41and to see if we could see evidence of the Apollo landings
0:19:41 > 0:19:42on its surface.
0:19:42 > 0:19:46So, we sent Pete out with his telescope to see what he could find.
0:19:46 > 0:19:48'Both men stand about the fourth rung up...'
0:19:48 > 0:19:51The Apollo missions captured the world's imagination
0:19:51 > 0:19:55from 1969 to 1972,
0:19:55 > 0:19:58when a total of 12 astronauts walked on the moon,
0:19:58 > 0:20:02and what remains of their equipment is still up there.
0:20:02 > 0:20:04The question is, can we see it?
0:20:04 > 0:20:08The first successful landing was Apollo 11,
0:20:08 > 0:20:11which set down in the now-famous Sea of Tranquillity,
0:20:11 > 0:20:14and that's going to be my first target this evening.
0:20:15 > 0:20:17With a three-inch telescope,
0:20:17 > 0:20:21you should be able to get a good view of the moon's surface.
0:20:22 > 0:20:27The Sea of Tranquillity is located just north and slightly east of the
0:20:27 > 0:20:30centre of the moon, it's this dark patch here.
0:20:30 > 0:20:32Now, the Apollo 11 landing site
0:20:32 > 0:20:36is located in a region just to the south
0:20:36 > 0:20:37of that dark patch.
0:20:37 > 0:20:42A great challenge is to try and find the three small craters which are
0:20:42 > 0:20:44located just in the north of the landing site.
0:20:44 > 0:20:47These are named after the Apollo 11 astronauts -
0:20:47 > 0:20:49Armstrong, Aldrin and Collins.
0:20:51 > 0:20:55To find them, locate the nearest noticeable crater,
0:20:55 > 0:20:577km-diameter Moltke,
0:20:57 > 0:21:00and look north to locate the three craters.
0:21:01 > 0:21:04As the largest is just 4.6km across,
0:21:04 > 0:21:07they can be difficult to spot,
0:21:07 > 0:21:10requiring at least an eight-inch scope and steady conditions.
0:21:11 > 0:21:14Unfortunately, you won't be able to see any remnants
0:21:14 > 0:21:16of the Apollo landing sites. In fact,
0:21:16 > 0:21:20it's impossible to see them with any ground-based telescope at all.
0:21:23 > 0:21:25'One. Ignition.
0:21:25 > 0:21:30- 'We're on our way, Houston! - Rates are good.'
0:21:30 > 0:21:33The largest piece of equipment left behind after each mission
0:21:33 > 0:21:37was the descent stage of the lunar module.
0:21:37 > 0:21:41At a measly 4.2 metres wide and 3.2 metres high,
0:21:41 > 0:21:43not even the Hubble Space Telescope
0:21:43 > 0:21:46has the optical resolution to see it.
0:21:51 > 0:21:54But although we can't see the remains of the lunar missions
0:21:54 > 0:21:56from the ground, it has been possible to image them
0:21:56 > 0:21:59using spacecraft orbiting the moon.
0:21:59 > 0:22:03The Lunar Reconnaissance Orbiter, which was launched in 2009,
0:22:03 > 0:22:07has imaged the lunar surface in unprecedented detail,
0:22:07 > 0:22:09and uncovered some of the relics
0:22:09 > 0:22:11left behind by the Apollo 11 mission.
0:22:11 > 0:22:14In this image, you can clearly see the lunar module,
0:22:14 > 0:22:17and you can even see some of the tracks which have been left behind
0:22:17 > 0:22:19on the moon's surface by Armstrong and Aldrin
0:22:19 > 0:22:22as they have explored the site.
0:22:24 > 0:22:27And the LRO spacecraft has also rediscovered the landing sites
0:22:27 > 0:22:30of the other Apollo missions.
0:22:30 > 0:22:32In 1971,
0:22:32 > 0:22:36Apollo 15 astronauts James Irwin and David Scott
0:22:36 > 0:22:38were the first to drive the lunar rover,
0:22:38 > 0:22:42and judging by the 17 miles of tyre tracks left behind,
0:22:42 > 0:22:45they clearly took it for a good spin.
0:22:45 > 0:22:49Interestingly, the pictures taken by the crews on the moon do reveal
0:22:49 > 0:22:53aspects of the landing sites we can see from Earth,
0:22:53 > 0:22:58and that's because the pictures show features of lunar geology.
0:23:00 > 0:23:02Behind this picture of the Apollo 15 lander,
0:23:02 > 0:23:07you can clearly see a lunar mountain, part of the Appennines,
0:23:07 > 0:23:10a mountain range you can see from the Earth
0:23:10 > 0:23:12even with a pair of binoculars.
0:23:12 > 0:23:14The closest large crater to the landing site
0:23:14 > 0:23:18is Archimedes, which is north of the moon's centre.
0:23:18 > 0:23:20The Appennines are the bright strip
0:23:20 > 0:23:22running beside it.
0:23:22 > 0:23:24Locate the part of the range
0:23:24 > 0:23:26closest to Archimedes
0:23:26 > 0:23:28to find the sinuous Hadley Rille,
0:23:28 > 0:23:31near to where Apollo 15 landed.
0:23:31 > 0:23:34The moon will be good for observing over the next week or so,
0:23:34 > 0:23:36so if you fancy having a go
0:23:36 > 0:23:38at trying to find the landing areas yourself,
0:23:38 > 0:23:42then you can find more information on our website.
0:23:47 > 0:23:49Before we reach the end of the show,
0:23:49 > 0:23:53there's one other popular request we should deal with.
0:23:53 > 0:23:56Daniel King and Jason Brighton, amongst others, wanted us to take
0:23:56 > 0:23:59a picture of an exoplanet orbiting another star.
0:23:59 > 0:24:01Now, that's no easy task,
0:24:01 > 0:24:03but several of the telescopes here on La Palma
0:24:03 > 0:24:06do spend their time trying to discover exoplanets.
0:24:14 > 0:24:17The most prolific planet-hunter on the island doesn't look like much.
0:24:17 > 0:24:22This unprepossessing shed houses SuperWASP, which is capable of
0:24:22 > 0:24:26monitoring the brightness of 800,000 stars at once,
0:24:26 > 0:24:28looking for the tiny dips in brightness
0:24:28 > 0:24:33which tell us that a planet has passed between us and the star.
0:24:33 > 0:24:36Between this installation and a replica in South Africa,
0:24:36 > 0:24:40SuperWASP has discovered more than 100 extrasolar planets.
0:24:46 > 0:24:49But tonight, we're not going to be using SuperWASP.
0:24:49 > 0:24:53We're going to be looking at another planet-hunting project
0:24:53 > 0:24:56hosted in the Italian Galileo Telescope.
0:25:00 > 0:25:02Wow! Look at this.
0:25:02 > 0:25:06This is the telescope Nazionale Galileo.
0:25:06 > 0:25:08I think Galileo would have been pleased with it.
0:25:08 > 0:25:10It looks enormous.
0:25:10 > 0:25:13It's even more impressive because of the closeness of these walls.
0:25:13 > 0:25:15If you have a look,
0:25:15 > 0:25:18the really exciting thing about this telescope is the mirror.
0:25:18 > 0:25:20If you come over here, this is the primary mirror,
0:25:20 > 0:25:23nearly four metres across. But look how thin it is.
0:25:23 > 0:25:26That thinness means it can flex to account for
0:25:26 > 0:25:29the movement of the atmosphere. It's called active optics,
0:25:29 > 0:25:34and it's the secret to why this is an excellent planet-hunting machine.
0:25:39 > 0:25:42It's hard to detect an exoplanet directly
0:25:42 > 0:25:44because the glare of the light
0:25:44 > 0:25:46from its neighbouring star is just too dazzling.
0:25:46 > 0:25:48So what we have to do instead
0:25:48 > 0:25:51is find indirect ways of telling that the planet's there.
0:25:51 > 0:25:54If you think about a planet in orbit around its star,
0:25:54 > 0:25:57then the planet's gravity must be pulling on that star,
0:25:57 > 0:26:01and the star will wobble back and forth as the planet orbits it.
0:26:01 > 0:26:04And so what we need is a way to tell if the star is wobbling,
0:26:04 > 0:26:06and that's what HARP does.
0:26:06 > 0:26:09It does that by looking at the spectrum of the star,
0:26:09 > 0:26:12and we can see what will happen if we look at a spectrum of the sun.
0:26:12 > 0:26:15So, you get the familiar rainbow pattern.
0:26:15 > 0:26:17But you also get these dark lines.
0:26:17 > 0:26:20And the lines mark the presence of particular elements.
0:26:22 > 0:26:25Now, the pattern of lines remains constant,
0:26:25 > 0:26:28but the whole spectrum shifts as the star moves.
0:26:28 > 0:26:32The spectrum becomes more red when the star is moving away from us,
0:26:32 > 0:26:34and more blue when it moves towards us.
0:26:34 > 0:26:37And it's that red-blue, red-blue pattern
0:26:37 > 0:26:41that indicates the presence of a planet around a star.
0:26:41 > 0:26:44And that is what the team here are hoping to find.
0:26:46 > 0:26:48In the control room,
0:26:48 > 0:26:52the Italian team train the telescope on individual stars,
0:26:52 > 0:26:54and take their spectra.
0:26:54 > 0:26:58The HARPS instrument is so sensitive that it can detect if the star is
0:26:58 > 0:27:00moving towards or away from us
0:27:00 > 0:27:03at speeds as low as one metre per second.
0:27:03 > 0:27:05That's walking pace.
0:27:06 > 0:27:11But one spectrum isn't enough to reveal the presence of a planet.
0:27:11 > 0:27:13The same star must be observed,
0:27:13 > 0:27:18and its rate of motion measured again and again over many nights.
0:27:19 > 0:27:22These are results from a star in the Beehive Cluster
0:27:22 > 0:27:27that was observed many times between 2013 and 2015.
0:27:29 > 0:27:31So, that's it. After all that work,
0:27:31 > 0:27:3570 nights of observation over two years, we're left with a graph.
0:27:35 > 0:27:38But it's a good graph. You can see from the way the star moves,
0:27:38 > 0:27:40this back and forth,
0:27:40 > 0:27:43it's this pattern that tells us there's a planet there.
0:27:43 > 0:27:46And so we can't get you an image of an exoplanet, I'm afraid,
0:27:46 > 0:27:49but I'm telling you, this is just as good.
0:28:01 > 0:28:03That's all we've got time for this month.
0:28:03 > 0:28:05And next month, there's no show.
0:28:05 > 0:28:07But you can still get your astronomical fix
0:28:07 > 0:28:11by watching Stargazing Live on BBC Two from 28th March.
0:28:11 > 0:28:14We'll be back in April to celebrate a very special anniversary -
0:28:14 > 0:28:17The Sky At Night's 60th birthday.
0:28:17 > 0:28:20Until then, get outside, get looking up.
0:28:20 > 0:28:22Good night.