0:00:26 > 0:00:29Hello and welcome to the Jodrell Bank Radio Observatory,
0:00:29 > 0:00:32home to the giant Lovell Telescope.
0:00:32 > 0:00:34In this programme, we are going to explore new perspectives
0:00:34 > 0:00:38because we are going to be listening to the sounds of the cosmos.
0:00:38 > 0:00:41It sounds bizarre, but we are going to be bringing you
0:00:41 > 0:00:44weird and wonderful noises from right across the universe
0:00:44 > 0:00:47including something that's never been heard before.
0:00:48 > 0:00:50Coming up, Lucie Green reveals
0:00:50 > 0:00:53how it is possible to see sounds on a distant star.
0:00:53 > 0:00:57There it is. That is what I've been after.
0:00:57 > 0:00:59We'll find out how sound waves sculpted
0:00:59 > 0:01:03the beautiful and complex universe that we see around us.
0:01:05 > 0:01:09That's the universe, 300,000 years after the big bang.
0:01:09 > 0:01:10What do you reckon?
0:01:10 > 0:01:13- That sounded like a car going past or something, didn't it?- It did a bit.
0:01:13 > 0:01:15I'll be talking with Tim O'Brien
0:01:15 > 0:01:19about one of the most evocative sounds in the universe.
0:01:20 > 0:01:22- Here we go.- I can see something coming through.
0:01:23 > 0:01:27'The sound of a star that has collapsed in on itself.'
0:01:27 > 0:01:30- It's like a heartbeat.- Exactly.
0:01:31 > 0:01:34We'll discover how to take amazing images of the night sky
0:01:34 > 0:01:36with just a mobile phone.
0:01:36 > 0:01:40The moon. That is amazing too. Wow!
0:01:43 > 0:01:47Everyone knows that in space no-one can hear you scream,
0:01:47 > 0:01:49and that is technically true.
0:01:49 > 0:01:51In the vacuum of space, sound waves can't travel.
0:01:51 > 0:01:54But there is plenty of sound in space.
0:01:54 > 0:01:57Imagine the crackling of lightning amongst the clouds of Jupiter.
0:01:57 > 0:02:00Imagine the whisper of the wind on Mars.
0:02:00 > 0:02:02All those sounds are trapped.
0:02:02 > 0:02:05To access them, we have to use our imaginations, our theories
0:02:05 > 0:02:06and our equations.
0:02:06 > 0:02:08By listening to these sounds,
0:02:08 > 0:02:10we get a new perspective on what's out there
0:02:10 > 0:02:13and see things that were previously hidden, even in our own star.
0:02:13 > 0:02:15There is a problem with the sun.
0:02:15 > 0:02:17When you look at it, you see what appears to be a broiling
0:02:17 > 0:02:19and beautiful surface
0:02:19 > 0:02:23but all the real action is happening deep beneath that surface.
0:02:23 > 0:02:26In fact, using sound is the only way that we can delve
0:02:26 > 0:02:28beneath that surface and see what is going on internally.
0:02:28 > 0:02:31That's just what Lucie Green has been doing.
0:02:32 > 0:02:37Our seemingly silent sun is actually alive with sound.
0:02:39 > 0:02:42These are the genuine sounds of our star,
0:02:42 > 0:02:45sped up to bring them into the range of human hearing.
0:02:49 > 0:02:52They're generated from deep below its surface
0:02:52 > 0:02:57and are a vital tool that's helped us understand its inner workings.
0:02:57 > 0:03:00I love listening to the sounds of the sun.
0:03:00 > 0:03:03They are so alien and they evoke a totally different character,
0:03:03 > 0:03:06a different side to the sun than the one I normally see
0:03:06 > 0:03:08when I'm studying it.
0:03:08 > 0:03:12The fact that we can listen to the sun at all is incredible.
0:03:12 > 0:03:17Between us and the sun is 93 million miles of essentially empty space.
0:03:17 > 0:03:18It is a vacuum out there
0:03:18 > 0:03:22and the sounds of the sun can't travel directly to us.
0:03:22 > 0:03:25Our ability to hear it and everything that we've learned
0:03:25 > 0:03:29along with that comes down to the very nature of what sound is.
0:03:31 > 0:03:34Sat here, I'm surrounded by sound -
0:03:34 > 0:03:38voices, clinking of cups, the whoosh of the coffee machine.
0:03:39 > 0:03:42All these sounds are created by the same basic process -
0:03:42 > 0:03:45vibrations.
0:03:46 > 0:03:50Vibrations that pass through the air to our ears.
0:03:54 > 0:03:56And the same is true within the sun.
0:03:58 > 0:04:02Turbulent regions of gas create sound on an epic scale.
0:04:04 > 0:04:07But it appears silent to us because there is no medium,
0:04:07 > 0:04:11no air or gas to transport the noise.
0:04:12 > 0:04:14However, we can detect these sounds
0:04:14 > 0:04:19because if you know the trick, it's possible to see sound.
0:04:20 > 0:04:24What we need is something called a Chladni plate and some salt.
0:04:25 > 0:04:27Give it a good covering.
0:04:28 > 0:04:31PLATE REVERBERATES
0:04:31 > 0:04:34You immediately see that the salt is starting to move.
0:04:37 > 0:04:39It is starting to take on a pattern.
0:04:42 > 0:04:44There it is, that is what I've been after.
0:04:44 > 0:04:48The salt takes on a pattern when I make the sound.
0:04:50 > 0:04:53The vibrations of the plate are creating the sound that
0:04:53 > 0:04:57goes into my ears and it is also moving the salt around.
0:04:58 > 0:05:02You can see that with each note I play, the pattern changes.
0:05:03 > 0:05:04Oh, beautiful.
0:05:09 > 0:05:11That is the key thing about these plates.
0:05:11 > 0:05:17The patterns that are created are unique for the particular sound
0:05:17 > 0:05:19and that means that even if I can't hear the sound,
0:05:19 > 0:05:22I can't hear the effect of those vibrations,
0:05:22 > 0:05:26I know what notes are being created by looking at the pattern.
0:05:30 > 0:05:32And it's that principle that allows us
0:05:32 > 0:05:35to tap into the sounds of our star.
0:05:36 > 0:05:38What I have here is an image of the sun
0:05:38 > 0:05:40taken by the Solar Dynamics Observatory
0:05:40 > 0:05:43and it's a colour-coded image.
0:05:43 > 0:05:47The black regions show us where gas is falling away from us
0:05:47 > 0:05:50and the white region is where the gas is rising up.
0:05:50 > 0:05:54It creates a very complex pattern.
0:05:54 > 0:05:57Essentially, it's exactly the same as we made here
0:05:57 > 0:05:58with our Chladni plates.
0:05:59 > 0:06:01Now, it may seem hard to believe,
0:06:01 > 0:06:04but we can extract from this rather messy image
0:06:04 > 0:06:06the very particular patterns
0:06:06 > 0:06:10that are associated to particular notes inside the sun.
0:06:10 > 0:06:14That is how we reconstruct the sounds that the sun has.
0:06:21 > 0:06:26What's truly fascinating is that through studying these sounds
0:06:26 > 0:06:30we can get a snapshot of the internal workings of our star...
0:06:32 > 0:06:35..thanks to work by people like Bill Chaplain.
0:06:35 > 0:06:37DEEP NOTE PLAYS
0:06:37 > 0:06:40- OK, that must be one of the big pipes.- Yes.
0:06:40 > 0:06:44Straight away, we can tell just from the low tones, low pitch,
0:06:44 > 0:06:48the low frequency of that that that's one of the biggest pipes.
0:06:48 > 0:06:51The frequencies at which pipes resonate, that tells us
0:06:51 > 0:06:54something about the size of the pipes,
0:06:54 > 0:06:57but also something about the gas inside the pipes.
0:06:57 > 0:06:59How does that relate to the sun
0:06:59 > 0:07:03and what we see as surface vibrations of the sun?
0:07:03 > 0:07:04The sun makes the sound naturally
0:07:04 > 0:07:08and it's trapped within the body of the sun, just in the same way
0:07:08 > 0:07:12that sound is trapped within the body of the pipes here.
0:07:12 > 0:07:15So the trapped sound makes the sun resonate
0:07:15 > 0:07:18but because the sun is a big ball of gas,
0:07:18 > 0:07:21the sound makes the sun gently breathe in and out.
0:07:21 > 0:07:25So we don't actually listen to the sun literally, what we do is,
0:07:25 > 0:07:28we are seeing the visible manifestation, if you like,
0:07:28 > 0:07:30of the sound trapped inside.
0:07:32 > 0:07:36Crucially, sound is affected by what it's travelling through.
0:07:37 > 0:07:39The changing temperature,
0:07:39 > 0:07:44density, even magnetic fields found in different parts of the sun
0:07:44 > 0:07:48all affect properties like the speed of sound trapped inside.
0:07:50 > 0:07:53And detecting these changes reveals the inner structure.
0:07:54 > 0:07:57It's a technique known as helioseismology.
0:07:59 > 0:08:03We knew that a sun-like star should have a core
0:08:03 > 0:08:05where we're burning hydrogen into helium.
0:08:05 > 0:08:08That's what's powering the star, driving its evolution.
0:08:08 > 0:08:12Then the outer parts of the sun, there we have conviction,
0:08:12 > 0:08:15so where we're moving energy from one place to the other
0:08:15 > 0:08:16literally by moving hot gas.
0:08:16 > 0:08:20But it was with helioseismology that we got the first measure,
0:08:20 > 0:08:25direct measurement of the depth of that outer convective layer.
0:08:25 > 0:08:30Also, we can measure the rate at which the material is spinning,
0:08:30 > 0:08:33and the profile that was found, actually,
0:08:33 > 0:08:37was not the one that theoreticians had predicted would be there.
0:08:37 > 0:08:41So that information that we've got on the rotation of the sun
0:08:41 > 0:08:44has been really important for people who are trying to understand
0:08:44 > 0:08:48how all of the magnetic activity, all of the magnetic structures,
0:08:48 > 0:08:51how those are generated on the sun.
0:08:51 > 0:08:54What I find amazing is that, by looking at the patterns
0:08:54 > 0:08:55on the surface of the sun,
0:08:55 > 0:08:59we can not only listen to the sounds of the sun,
0:08:59 > 0:09:02we can also delve deep underneath its surface
0:09:02 > 0:09:05and we can track and predict its future activity.
0:09:05 > 0:09:08It's an insight that would simply be beyond us
0:09:08 > 0:09:11if it wasn't for the music of our star.
0:09:19 > 0:09:21There are sounds throughout the cosmos
0:09:21 > 0:09:25but, depending on where you are, not all sounds sound the same.
0:09:27 > 0:09:29We're used to sound travelling through
0:09:29 > 0:09:32the atmosphere of the Earth, but we can think about
0:09:32 > 0:09:34what sound would be like on other planets, as well.
0:09:34 > 0:09:37We have some software from the University of Southampton
0:09:37 > 0:09:39that will let us take our voices and send them to Venus,
0:09:39 > 0:09:41so I think we should give that a go.
0:09:41 > 0:09:43I'm going to give you the microphone.
0:09:43 > 0:09:44Great, I get the microphone.
0:09:44 > 0:09:47I'm going to press record, and you say something, OK?
0:09:47 > 0:09:50So, what would my voice sound like on other planets?
0:09:50 > 0:09:51Well, good question!
0:09:51 > 0:09:53Well, the software will now process this.
0:09:53 > 0:09:56So this is based on atmosphere, density, various other parameters?
0:09:56 > 0:09:57That's right.
0:09:57 > 0:10:00VERY DEEP VOICE: 'So what would my voice sound like on other planets?'
0:10:00 > 0:10:03You sound like me! That's actually pretty close!
0:10:03 > 0:10:06I feel like a space invader or something - "Take us to your leader!"
0:10:06 > 0:10:08What's happening there is two things.
0:10:08 > 0:10:12The atmosphere on Venus is this dense mix of carbon dioxide
0:10:12 > 0:10:15and a bit of sulphuric acid, so not a good place to be.
0:10:15 > 0:10:19But that density changes the way your vocal cords vibrate
0:10:19 > 0:10:21and also how the sound's transmitted,
0:10:21 > 0:10:22because the speed of sound is different.
0:10:22 > 0:10:25So it's just like in water, sound actually travels faster,
0:10:25 > 0:10:29so the more dense the atmosphere, the quicker the sound will travel,
0:10:29 > 0:10:31and therefore you get a change in the voice.
0:10:31 > 0:10:33But that was quite distinctive, wasn't it?
0:10:33 > 0:10:35Yeah, absolutely, it does illustrate this point
0:10:35 > 0:10:39that what you sound like depends on where in the solar system you are.
0:10:44 > 0:10:46Now, we're here at Jodrell Bank,
0:10:46 > 0:10:48and the focus of much of the research done from this facility
0:10:48 > 0:10:50is on pulsars.
0:10:52 > 0:10:56Pulsars are extraordinary stars that emit beams of radiation
0:10:56 > 0:10:58that make them appear to flash.
0:10:59 > 0:11:01The team here at Jodrell are hoping that they will help them
0:11:01 > 0:11:04to solve one of the great mysteries of astronomy.
0:11:05 > 0:11:09To study them, they use the massive Lovell Telescope.
0:11:09 > 0:11:11Its dish is over 75 metres wide
0:11:11 > 0:11:14and it observes the cosmos using radio waves.
0:11:17 > 0:11:18So, Tim, we're there to look at pulsars,
0:11:18 > 0:11:21but pulsars are a special case of a neutron star.
0:11:21 > 0:11:23I find neutron stars a bit freaky,
0:11:23 > 0:11:27because it's something about one and a half times the mass of the sun,
0:11:27 > 0:11:29- that could fit in Sheffield. - Exactly, yes.
0:11:29 > 0:11:33It's a dead star, it's the core of an exploded star,
0:11:33 > 0:11:36so when the star explodes in the supernova, the core collapses
0:11:36 > 0:11:38to make this incredibly dense object.
0:11:38 > 0:11:40These things, the exciting thing for us
0:11:40 > 0:11:43is that these things are spinning, but we can see them
0:11:43 > 0:11:45because they actually beam out light -
0:11:45 > 0:11:49and in our case we're interested in the radio waves they beam out -
0:11:49 > 0:11:51from the magnetic poles.
0:11:51 > 0:11:54And just like the Earth, you know the Earth's magnetic north
0:11:54 > 0:11:55- and magnetic south are offset... - Yes.
0:11:55 > 0:11:57..with respect to the sort of north pole,
0:11:57 > 0:11:59the same is true for the neutron star,
0:11:59 > 0:12:03so as it spins, the magnetic poles sweep around like that,
0:12:03 > 0:12:06and that means that the beam that comes out from them
0:12:06 > 0:12:07sweeps around the sky.
0:12:07 > 0:12:10And every time it comes past us, we see a flash.
0:12:10 > 0:12:12- So just like a lighthouse. - Exactly, it's a cosmic lighthouse
0:12:12 > 0:12:14spinning in the sky.
0:12:14 > 0:12:16We see flash, flash, flash from the pulsar.
0:12:16 > 0:12:19And we're going to demonstrate that live with the Lovell Telescope now,
0:12:19 > 0:12:22so I don't know, I think Ian, our telescope controller,
0:12:22 > 0:12:25will move the telescope on source.
0:12:25 > 0:12:26Fantastic.
0:12:26 > 0:12:29If you come and have a look at the screen over here, basically,
0:12:29 > 0:12:32we've turned those radio waves into a sound
0:12:32 > 0:12:33and we can listen to that noise.
0:12:33 > 0:12:35STATIC CRACKLES
0:12:35 > 0:12:36And then what will happen
0:12:36 > 0:12:39as the telescope gradually swings onto the pulsar...
0:12:41 > 0:12:44- Oh, here we go.- I can see something coming through.
0:12:44 > 0:12:47REGULAR THUDDING
0:12:47 > 0:12:49- And that's it?- That's it. - That's the pulsar?
0:12:49 > 0:12:50That's the pulsar spinning.
0:12:50 > 0:12:53Spinning around, sending that beam, that radio beam into space?
0:12:53 > 0:12:55And you can hear the...
0:12:55 > 0:12:57dum, dum, dum, dum, dum, dum...
0:12:57 > 0:12:59- It's like a heartbeat?- Yeah, exactly.
0:12:59 > 0:13:01That is a dead star, weighing more than the sun,
0:13:01 > 0:13:05spinning about three times a second, 26,000 light years away,
0:13:05 > 0:13:08which is really exciting because, actually,
0:13:08 > 0:13:11we've only just set the system up for you today
0:13:11 > 0:13:12to listen to this pulsar now.
0:13:12 > 0:13:14It is fantastic.
0:13:14 > 0:13:15THUDDING CONTINUES
0:13:15 > 0:13:18So pulsars seem to be fascinating, but why are they useful?
0:13:18 > 0:13:20Yeah. I mean, they're actually, this...
0:13:20 > 0:13:22I'll turn that down so we can talk.
0:13:22 > 0:13:25The key role is in testing extreme physics.
0:13:25 > 0:13:29One of the key projects that we're using that the pulsar group here
0:13:29 > 0:13:32and elsewhere in the world are working on with telescopes like this
0:13:32 > 0:13:36at the moment is to use pulsar to try and detect gravitational waves.
0:13:36 > 0:13:38I think you should say "The elusive gravitational wave."
0:13:38 > 0:13:39I definitely should!
0:13:39 > 0:13:43These things were predicted by Einstein 100 years ago,
0:13:43 > 0:13:45but we've not yet directly detected them.
0:13:45 > 0:13:47They're actually really bizarre things,
0:13:47 > 0:13:49they're ripples in space-time.
0:13:49 > 0:13:52So if you can imagine somewhere on the other side of the universe
0:13:52 > 0:13:55there's two massive black holes at the centre of the galaxy,
0:13:55 > 0:13:57say two galaxies have merged.
0:13:57 > 0:14:00These black holes are spiralling around one another.
0:14:00 > 0:14:03They produce this expanding pattern of ripples in space...
0:14:03 > 0:14:06- The gravitational waves? - Exactly, the gravitational waves
0:14:06 > 0:14:08travel through space at the speed of light.
0:14:08 > 0:14:10If there was one coming through us now,
0:14:10 > 0:14:12which there almost certainly is,
0:14:12 > 0:14:15we're gradually being stretched in one direction,
0:14:15 > 0:14:18and perpendicular to that we're being squashed.
0:14:18 > 0:14:21So I suppose that's quite a distinctive signature to pick up?
0:14:21 > 0:14:22It is. It's what you would look for.
0:14:22 > 0:14:25You might imagine that what you'd look for is whether something
0:14:25 > 0:14:29is simply longer or shorter as the gravitational wave goes past,
0:14:29 > 0:14:32but the trouble is, the amount by which space is stretched
0:14:32 > 0:14:35is tiny, so in the case of the ones we're trying to pick up
0:14:35 > 0:14:37with the pulsars, it's a bit like the distance
0:14:37 > 0:14:40between the Earth and the moon being changed
0:14:40 > 0:14:44- by about one hundredth of the width of a human hair.- Oooh!
0:14:44 > 0:14:47- It is accuracy. - The measurement is very hard to do.
0:14:47 > 0:14:50What's key about pulsars in this case is,
0:14:50 > 0:14:53they're very stable clocks, effectively,
0:14:53 > 0:14:56so we heard the thud, thud, thud, thud of the pulsar,
0:14:56 > 0:14:58three times a second.
0:14:58 > 0:15:01Because you've got so much mass spinning at that speed,
0:15:01 > 0:15:03it's a very stable system.
0:15:03 > 0:15:04What sort of accuracy are we talking?
0:15:04 > 0:15:08We're talking about measuring those periods to an accuracy
0:15:08 > 0:15:11of basically a nanosecond, so a billionth of a second.
0:15:11 > 0:15:16As space is squashed and stretched as a gravitational wave passes by,
0:15:16 > 0:15:19those pulses are bunched together or stretched apart.
0:15:19 > 0:15:23- So you'll see a slight change in the timing of those pulses?- Exactly.
0:15:23 > 0:15:26- So when do you think you'll see one? - Yeah, this is the key.
0:15:26 > 0:15:28Sometime in the next few years
0:15:28 > 0:15:31we might well detect a gravitational wave.
0:15:31 > 0:15:32In a sense, it's a risk.
0:15:32 > 0:15:34We're learning things as we go along,
0:15:34 > 0:15:36as we gather more and more data, but, yeah,
0:15:36 > 0:15:38great hope for this technique.
0:15:38 > 0:15:40I think that's fantastic, thank you so much.
0:15:47 > 0:15:51Next, Pete Lawrence has ventured outside to bring us his star guide.
0:15:51 > 0:15:55But first, he's going to show us how to take fabulous images
0:15:55 > 0:15:58of the night sky with something many of us have in our pockets.
0:16:00 > 0:16:02All you need is one of these, a telescope,
0:16:02 > 0:16:04and something as simple as this -
0:16:04 > 0:16:06a smartphone with a camera in it.
0:16:06 > 0:16:09Now, you might not think that the camera on a smartphone
0:16:09 > 0:16:12is sensitive enough to be able to take astronomical photographs,
0:16:12 > 0:16:16but it is, especially if the target is big and bright.
0:16:16 > 0:16:19Now, the one thing which really fits that bill perfectly
0:16:19 > 0:16:21is, of course, the moon.
0:16:22 > 0:16:25'To see details on the moon's surface, you need shadows,
0:16:25 > 0:16:28'so you'll get the best images when the moon isn't full.'
0:16:30 > 0:16:33'Start by holding the phone away from the eyepiece.'
0:16:33 > 0:16:36Then I'm going to move it in close and closer,
0:16:36 > 0:16:38following the bright dot down.
0:16:38 > 0:16:41'This is actually a bit trickier than it looks
0:16:41 > 0:16:45'because of the way the lenses in the phone and the eyepiece interact,
0:16:45 > 0:16:46'but keep at it.'
0:16:46 > 0:16:50- There it goes. And I can just take a shot. - CAMERA CLICKS
0:16:50 > 0:16:53And, oh, that's a nice one.
0:16:53 > 0:16:54Look at that.
0:16:54 > 0:16:58And I'm actually quite pleased with that, it's quite a nice image.
0:16:58 > 0:17:01There are lots of amazing things to see on the surface of the moon,
0:17:01 > 0:17:03and to find a selection of the best,
0:17:03 > 0:17:06check out the moon guides on our website...
0:17:12 > 0:17:14'For the last few days, some members
0:17:14 > 0:17:18'of the Breckland Astronomical Society have been experimenting
0:17:18 > 0:17:20'with smartphone photography.
0:17:20 > 0:17:23'They've even managed to capture an image of Jupiter.'
0:17:24 > 0:17:27- Wow! That is...- It's not too bad. It shows up.
0:17:27 > 0:17:30But you've got the main belts coming through there,
0:17:30 > 0:17:33and I bet that if the great red spot were visible on that disc,
0:17:33 > 0:17:35you would actually pick that up.
0:17:35 > 0:17:37- I reckon I would have got it, yeah. - Which is amazing.
0:17:37 > 0:17:41But the other thing that comes out, because Jupiter is a gas planet
0:17:41 > 0:17:45which rotates very rapidly, it's squashed, so it looks
0:17:45 > 0:17:48not like a circle, it looks like the circle has been squashed,
0:17:48 > 0:17:50and you can actually pick that out on that,
0:17:50 > 0:17:53very clearly, actually, that the planet looks less wide
0:17:53 > 0:17:56from top to bottom than it is from left to right.
0:17:56 > 0:17:59Incredible. Absolutely amazing result.
0:17:59 > 0:18:02Ah, the moon! One of my favourite objects.
0:18:02 > 0:18:05That is amazing, too! Wow!
0:18:05 > 0:18:06It was a four inch refractor.
0:18:06 > 0:18:09Look at that, that is just incredible.
0:18:09 > 0:18:11You know, a few years ago you would have taken a picture
0:18:11 > 0:18:14with a digital camera and you'd have been very happy with that.
0:18:14 > 0:18:16And this is with a smartphone.
0:18:16 > 0:18:19The hardest part I found, of course, is trying to get it lined up
0:18:19 > 0:18:22and get it centred. Hold it steady enough to get a steady image.
0:18:22 > 0:18:24That's it, isn't it? Yeah.
0:18:24 > 0:18:26Well, that is quite a fantastic image.
0:18:26 > 0:18:30- You should be very proud of that. - Thank you.- Thank you very much.
0:18:31 > 0:18:34Now, there's lots of interest in this month's night sky,
0:18:34 > 0:18:37but I think the highlights have to be the planets.
0:18:37 > 0:18:39Here is my star guide to what's coming up.
0:18:43 > 0:18:45As darkness falls on the 16th,
0:18:45 > 0:18:47Jupiter is due south,
0:18:47 > 0:18:49two thirds of the way up the sky.
0:18:50 > 0:18:52If you have a telescope,
0:18:52 > 0:18:54look at Jupiter's disc between 10:30pm
0:18:54 > 0:18:57and just past midnight to see a rare event.
0:18:57 > 0:19:00The shadows of Io and Ganymede,
0:19:00 > 0:19:03two of Jupiter's large Galilean moons,
0:19:03 > 0:19:05will be crossing the planet.
0:19:05 > 0:19:07In the hours following midnight,
0:19:07 > 0:19:09locate the Plough, which is overhead.
0:19:10 > 0:19:12Follow the natural curve of its handle
0:19:12 > 0:19:13away from the pan to locate
0:19:13 > 0:19:16the bright orange star, Arcturus.
0:19:18 > 0:19:23Continue the curve to arrive at brilliant white Spica.
0:19:23 > 0:19:27The bright, salmon pink object above Spica is Mars.
0:19:28 > 0:19:32A little less than two outstretched hands to the left
0:19:32 > 0:19:35and slightly below Spica is the yellow-hued planet Saturn.
0:19:38 > 0:19:40On 27th March
0:19:40 > 0:19:42there is also a daytime treat.
0:19:42 > 0:19:46Using your eyes, try to find the moon at 9:20 in the morning,
0:19:46 > 0:19:49being careful not to look at the sun.
0:19:49 > 0:19:51Five moon-widths below the crescent,
0:19:51 > 0:19:54Venus will be shining away in the blue sky.
0:19:57 > 0:19:59Well, now back to sound.
0:19:59 > 0:20:02Tim has created an audio tour of the universe for us,
0:20:02 > 0:20:05including some things that no-one's ever heard before.
0:20:05 > 0:20:06Tim, where shall we start?
0:20:06 > 0:20:09The plan is to start close and then work our way out.
0:20:09 > 0:20:14We'll start with Jupiter, and these are sounds from signals
0:20:14 > 0:20:18that the Voyager 1 spacecraft recorded as it passed by Jupiter.
0:20:18 > 0:20:20Let's have a listen.
0:20:22 > 0:20:27WHINING AND WHISTLING
0:20:29 > 0:20:31I don't think I expected that.
0:20:31 > 0:20:34No, it does sound a bit like a dawn chorus.
0:20:34 > 0:20:35- It does.- But screechier!
0:20:35 > 0:20:39- It's a rather more erratic... - Pterodactyls or something!
0:20:39 > 0:20:41Yeah, rather than lovely hummingbirds.
0:20:41 > 0:20:45No, it's actually called the Jovian chorus, the Jupiter chorus.
0:20:45 > 0:20:49These chorus waves are actually produced by electrons
0:20:49 > 0:20:52that are spiralling around the magnetic field of Jupiter,
0:20:52 > 0:20:55so from the north magnetic pole to the south magnetic pole,
0:20:55 > 0:20:58and as they spiral around they produce these radio waves
0:20:58 > 0:21:00that we've turned into a sound here.
0:21:02 > 0:21:04SOUND CONTINUES
0:21:04 > 0:21:06So we can hear this delightful noise!
0:21:06 > 0:21:08I think we've probably heard enough Jupiter.
0:21:08 > 0:21:10- Excellent, good. - Turned off on cue.
0:21:10 > 0:21:11Where shall we go next?
0:21:11 > 0:21:14We're going to actually stick with Voyager, actually.
0:21:14 > 0:21:17We're going to carry on with Voyager back until just a few years ago,
0:21:17 > 0:21:19when Voyager left the heliosphere,
0:21:19 > 0:21:22basically the edge of the volume of space
0:21:22 > 0:21:23that's influenced by the sun.
0:21:23 > 0:21:27WAVERING HIGH TONE
0:21:29 > 0:21:32What you're hearing is the rate of cosmic ray particles
0:21:32 > 0:21:36hitting the detectors on Voyager.
0:21:36 > 0:21:38So, high-pitched, lots of particles.
0:21:38 > 0:21:40- TONE DROPS SUDDENLY BOTH:- Whoa!
0:21:40 > 0:21:42- That's quite significant! - And that was it.
0:21:42 > 0:21:44That was the point at which it left the heliosphere.
0:21:44 > 0:21:46And that marks the end of our solar system, effectively.
0:21:46 > 0:21:49Yeah, so those particles are sort of trapped by the magnetic field
0:21:49 > 0:21:53of the sun, and as it passed over that invisible boundary, actually,
0:21:53 > 0:21:56where those particles are gathered, then you hear the flux,
0:21:56 > 0:21:59the numbers of those cosmic rays drop significantly,
0:21:59 > 0:22:01which you heard in the sound there.
0:22:01 > 0:22:03I find it fantastic, because Voyager was launched in 1977,
0:22:03 > 0:22:07travelling at 10.5 miles a second out to the edge of the solar system,
0:22:07 > 0:22:09and now it is officially beyond.
0:22:09 > 0:22:11Our first interstellar messenger, basically.
0:22:11 > 0:22:12And still sending back information.
0:22:12 > 0:22:15But, Tim, I want to ask you about your own research,
0:22:15 > 0:22:18because something rather exciting happened just a few weeks ago.
0:22:18 > 0:22:20So I spend a lot of my time working on things called novae.
0:22:20 > 0:22:23We now know they're stars exploding and becoming very bright
0:22:23 > 0:22:26and one of these popped up in the constellation of Scorpius
0:22:26 > 0:22:28just a few weeks ago, and we've been monitoring it
0:22:28 > 0:22:30with telescopes around the world.
0:22:30 > 0:22:33Actually, what we'll play now is the sound of the data
0:22:33 > 0:22:37- from an x-ray telescope on board the Swift spacecraft.- OK.
0:22:38 > 0:22:41STEADY HIGH-PITCHED TONE
0:22:42 > 0:22:49LOWER TONE GROWS IN INTENSITY
0:22:49 > 0:22:51LOWER TONE FADES
0:22:53 > 0:22:56Come on, you're grinning. Tell us what you heard.
0:22:56 > 0:22:59- Let you in on the secret.- So there's two distinct tones there, I think.
0:22:59 > 0:23:03There are, yeah, and what you're hearing are basically the x-rays
0:23:03 > 0:23:05coming from this explosion,
0:23:05 > 0:23:08and there's actually two dominant parts to the x-ray emission.
0:23:08 > 0:23:11So, first of all, what you heard was a high-frequency tone.
0:23:11 > 0:23:15That comes from the shockwave that's ripping out from this explosion
0:23:15 > 0:23:18through the wind of the red giant star that's in this system,
0:23:18 > 0:23:20and that produces high-energy x-rays
0:23:20 > 0:23:22which come into that sound as a high-pitched tone.
0:23:22 > 0:23:24So this is just ripping through the material
0:23:24 > 0:23:26- that's surrounding the white dwarf? - Exactly, yeah.
0:23:26 > 0:23:28So the explosion happens to the white dwarf,
0:23:28 > 0:23:30the shockwave expands out, very hot gas,
0:23:30 > 0:23:33very high-energy x-rays that you hear as the high-pitched tone.
0:23:33 > 0:23:36As that expands out you start to see through it,
0:23:36 > 0:23:39and what you see is the surface of the hot white dwarf
0:23:39 > 0:23:42that's left behind in the centre where the explosion occurred.
0:23:42 > 0:23:45That also produces x-rays, but it's rather cooler,
0:23:45 > 0:23:47they're rather lower energy x-rays,
0:23:47 > 0:23:50and that comes in as the lower frequency tone.
0:23:50 > 0:23:53And that actually dominates, that becomes very bright for a while,
0:23:53 > 0:23:55but then as the hot gas on the white dwarf is all used up,
0:23:55 > 0:23:59then that fades away and then, coming back, underneath it all
0:23:59 > 0:24:02you hear the high pitch of the shockwave still expanding
0:24:02 > 0:24:04out into interstellar space.
0:24:04 > 0:24:07Excellent. Well, I'm glad we heard it and we've now travelled
0:24:07 > 0:24:10to a distant star, but we need to go much further than that,
0:24:10 > 0:24:12to the edge of the observable universe,
0:24:12 > 0:24:14because sound waves that once echoed there
0:24:14 > 0:24:17formed everything that we see around us today.
0:24:21 > 0:24:23Sound waves are a key part
0:24:23 > 0:24:25of one of the most famous images in science -
0:24:25 > 0:24:29the cosmic microwave background, or CMB.
0:24:31 > 0:24:35This is the oldest light left in the universe, and it forms a picture
0:24:35 > 0:24:40of what the cosmos was like only 300,000 years after the big bang.
0:24:42 > 0:24:46To discuss the role of sound waves that we can see in the CMB,
0:24:46 > 0:24:48I'm meeting Sarah Bridle,
0:24:48 > 0:24:51and I've brought with me an interesting recording.
0:24:52 > 0:24:54We're going to talk about the early universe,
0:24:54 > 0:24:56which was a very different place
0:24:56 > 0:24:58from the one we see around us today, so what was it like?
0:24:58 > 0:25:02Well, so, early in the universe the universe was much denser.
0:25:02 > 0:25:05So, basically, today we've got a vacuum in space.
0:25:05 > 0:25:07But if we go back in time to the early universe
0:25:07 > 0:25:10the universe was much smaller, everything was much closer together,
0:25:10 > 0:25:14and we had this soup of elementary particles,
0:25:14 > 0:25:16protons, electrons and neutrons,
0:25:16 > 0:25:19and they're all much closer together.
0:25:19 > 0:25:22That means you can get sound travelling through the universe.
0:25:22 > 0:25:24Right, so today the universe is virtually a vacuum,
0:25:24 > 0:25:26but back then the sound waves
0:25:26 > 0:25:28could propagate through this dense medium.
0:25:28 > 0:25:31Excellent - if you had any sound waves.
0:25:31 > 0:25:34- So what we need is a source of sound.- OK, yes.
0:25:34 > 0:25:36Then some patches were clumpier than others,
0:25:36 > 0:25:39so there is more stuff in one place and less in somewhere else.
0:25:39 > 0:25:41Then gravity comes in.
0:25:41 > 0:25:44As things pull together, then they heat up,
0:25:44 > 0:25:47so the universe is getting clumpier and hotter
0:25:47 > 0:25:48in this patch of the universe.
0:25:48 > 0:25:52And then, actually, it gets so hot that it pushes itself apart again.
0:25:52 > 0:25:54Just because the particles are moving.
0:25:54 > 0:25:56The particles are moving and it's getting hotter,
0:25:56 > 0:25:59and the pressure of that heat pushes it apart again,
0:25:59 > 0:26:02and then gravity pulls it back in again, pressure pushes it apart.
0:26:02 > 0:26:04So we've got this oscillation,
0:26:04 > 0:26:08this wobbling going on in the early universe, which is a sound wave.
0:26:08 > 0:26:09So I've actually got a recording
0:26:09 > 0:26:13- of what the sound would have been like at that point.- Right.
0:26:13 > 0:26:15We've moved it up 50 octaves so we can hear it,
0:26:15 > 0:26:18it's a very low note, but we've moved it up
0:26:18 > 0:26:19so I hope you find this impressive.
0:26:19 > 0:26:24WHOOSHING
0:26:25 > 0:26:28There you go, that's the universe 300,000 years after the big bang.
0:26:28 > 0:26:29What do you reckon?
0:26:29 > 0:26:32- Well, that sounded like a car going past, didn't it?- It did a bit!
0:26:32 > 0:26:34It's a complicated noise, though.
0:26:34 > 0:26:36To see them we have to tune ourselves
0:26:36 > 0:26:38into the microwave region of the spectrum.
0:26:38 > 0:26:41Right, so at that time the light is travelling around
0:26:41 > 0:26:43in the early universe and it's optical light,
0:26:43 > 0:26:44so we could see it with our eyes.
0:26:44 > 0:26:46If you were standing there. It's not advised!
0:26:46 > 0:26:49It wouldn't be very nice, so we shouldn't go there.
0:26:49 > 0:26:52But it's light, like we can see with our eyes,
0:26:52 > 0:26:55but now, as the universe has expanded,
0:26:55 > 0:26:59those light waves have stretched out, and so they become microwaves,
0:26:59 > 0:27:03and so we can look with special radio telescopes at these microwaves
0:27:03 > 0:27:07and we can see a picture of the light which is coming towards us,
0:27:07 > 0:27:10that's been travelling to us all that time
0:27:10 > 0:27:13since the universe was just 300,000 years old.
0:27:13 > 0:27:14And we've got that picture here,
0:27:14 > 0:27:17so this is a picture of the whole sky taken by Planck,
0:27:17 > 0:27:18which is the European satellite
0:27:18 > 0:27:21that's just made the best ever map of this light.
0:27:21 > 0:27:24What can we see here and how does it relate
0:27:24 > 0:27:25to what we were just talking about?
0:27:25 > 0:27:29Well, we can see these sound waves. We're taking a snapshot,
0:27:29 > 0:27:33basically, of what these sound waves were like in the early universe.
0:27:33 > 0:27:35We can see these red and blue patches.
0:27:35 > 0:27:39So where the red patches are, that's where the universe
0:27:39 > 0:27:42was hotter and denser, really clumped together,
0:27:42 > 0:27:45and then that patch would have expanded afterwards,
0:27:45 > 0:27:49but the blue patches here are where it was cooler and more spread out.
0:27:49 > 0:27:53So, in fact, those hot patches where there's lots of stuff,
0:27:53 > 0:27:56that would have then gone on to form the first stars
0:27:56 > 0:27:59and galaxies that we can see today.
0:27:59 > 0:28:00So this is a recent image.
0:28:00 > 0:28:03Planck delivered its results a year or so ago now.
0:28:03 > 0:28:07Is there more to learn from looking at the microwave background
0:28:07 > 0:28:08in the early universe?
0:28:08 > 0:28:11Well, Planck also has polarised sunglasses, effectively, on it,
0:28:11 > 0:28:14so we're going to learn about the direction of the light,
0:28:14 > 0:28:16which will tell us even more about
0:28:16 > 0:28:17how much stuff there is in the universe.
0:28:17 > 0:28:20Fab. Well, I hope you'll come back and tell us about that,
0:28:20 > 0:28:21and you never know,
0:28:21 > 0:28:24we might have found a more aesthetically pleasing recording
0:28:24 > 0:28:25of the early universe by then.
0:28:25 > 0:28:26- Thanks a lot.- Thanks a lot.
0:28:32 > 0:28:35That's it for now, but do remember to send your smartphone pictures in
0:28:35 > 0:28:37and we'll put them up on our website.
0:28:37 > 0:28:40When we come back next month we'll be talking about Mars
0:28:40 > 0:28:43and what ten years of robots roving around the planet have told us.
0:28:43 > 0:28:46And Mars is really prominent in the sky at the moment,
0:28:46 > 0:28:48so remember, get outside and get looking up.
0:28:48 > 0:28:49Good night.