0:00:03 > 0:00:07Last month, scientists announced that they had detected something
0:00:07 > 0:00:10never seen before -
0:00:10 > 0:00:13two massive neutron stars colliding with each other,
0:00:13 > 0:00:15triggering a colossal explosion.
0:00:23 > 0:00:28It marks the most dramatic example so far of a new type of astronomy
0:00:28 > 0:00:32that focuses on brief transitory events that happen so fast
0:00:32 > 0:00:34they're almost impossible to detect.
0:00:35 > 0:00:37Welcome to the spectacular world
0:00:37 > 0:00:40of astronomy that happens in the blink of an eye.
0:01:10 > 0:01:13We're used to thinking that the universe operates on timescales
0:01:13 > 0:01:16of millions or even billions of years.
0:01:18 > 0:01:21Most change happens with imperceptible slowness.
0:01:23 > 0:01:26We have now discovered a whole catalogue of events like the
0:01:26 > 0:01:30neutron star collision that happen on much shorter timescales,
0:01:30 > 0:01:33seconds or even milliseconds.
0:01:33 > 0:01:36Tonight, we explore this world of transitory events.
0:01:38 > 0:01:41I'm here at Jodrell Bank to find out the latest theories about the
0:01:41 > 0:01:46most mysterious of all transitory events - fast radio bursts.
0:01:48 > 0:01:52We'll hear more about the recently detected neutron star collision
0:01:52 > 0:01:53and gravitational wave.
0:01:57 > 0:02:02Chris joins astronomers attempting to detect gamma ray bursts
0:02:02 > 0:02:05- the most powerful short-term event that we know of -
0:02:05 > 0:02:08to see just how different this kind of astronomy is.
0:02:10 > 0:02:12We could say possible burst if you want.
0:02:12 > 0:02:14I don't know what I want. I don't know.
0:02:16 > 0:02:18And here it is...
0:02:18 > 0:02:21And Lucie Green reveals that some dramatic rapid phenomena
0:02:21 > 0:02:23can occur much closer to home.
0:02:30 > 0:02:34But we start with Chris, who spent a couple of days with scientists
0:02:34 > 0:02:38attempting to detect an elusive gamma ray burst.
0:02:42 > 0:02:46Astronomy used to be about staring up at the unchanging heavens,
0:02:46 > 0:02:50so the search for transience, things that go bang in the night,
0:02:50 > 0:02:52is truly revolutionary.
0:02:52 > 0:02:57But it all depends on astronomers' ability to monitor the whole sky.
0:02:58 > 0:03:01So I've come to the University of Leicester to see how this is done.
0:03:05 > 0:03:08This is the UK base of Swift,
0:03:08 > 0:03:13a space-based telescope designed to search for GRBs, gamma ray bursts.
0:03:16 > 0:03:20Brilliant flashes of light that last just for a few seconds.
0:03:22 > 0:03:26It's thought that some of them are caused by neutron stars
0:03:26 > 0:03:27collapsing into black holes.
0:03:31 > 0:03:36The problem is that they're rare, and so Swift has to do two things.
0:03:36 > 0:03:41First, it has to scan the whole sky to spot when a GRB occurs,
0:03:41 > 0:03:45and then second, it has to swerve to get the data before it disappears.
0:03:50 > 0:03:53So we're here because you're controlling the spacecraft.
0:03:53 > 0:03:56This is not what I thought Mission Control would look like!
0:03:56 > 0:03:58So, what's your role?
0:03:58 > 0:04:03I am one of a team of observatory duty scientists, ODS for short.
0:04:03 > 0:04:05Everything is so well designed now.
0:04:05 > 0:04:08As long as you have access to a computer, and you can login
0:04:08 > 0:04:11to the relevant computers, we can do everything.
0:04:11 > 0:04:15So, how quickly can Swift respond once it's detected something?
0:04:15 > 0:04:19Quickly. The maximum speed we can slew at is about a degree a second.
0:04:19 > 0:04:23This typically means that, for most gamma ray bursts that we detect,
0:04:23 > 0:04:26we'll be on target between one to two minutes.
0:04:26 > 0:04:28And that's important for the science?
0:04:28 > 0:04:31It is, yes. Gamma ray bursts may be the brightest explosions
0:04:31 > 0:04:35in the universe since the Big Bang, but they fade really quickly,
0:04:35 > 0:04:37so you have to get on there as fast as you can.
0:04:37 > 0:04:39- And if you're not swift, you miss it.- Exactly.
0:04:43 > 0:04:46At 8.33am, there's an alarm.
0:04:46 > 0:04:48Swift has spotted something.
0:04:53 > 0:04:56Phil Evans, the BA, or burst advocate,
0:04:56 > 0:04:59immediately starts to analyse the new data.
0:05:01 > 0:05:04And Kim gets on the line to her counterpart at the Goddard Space
0:05:04 > 0:05:08Flight Centre in Maryland, to see if they've noticed the same event.
0:05:08 > 0:05:11Hi, Amy. It's Kim and the Leicester crowd.
0:05:12 > 0:05:16Yes, it's NGC 224 that is the nearby source.
0:05:22 > 0:05:26You mean, the one big spike before the...?
0:05:26 > 0:05:27- Yeah. - Yeah.
0:05:27 > 0:05:29Could it be an SGR in M31?
0:05:29 > 0:05:32I mean, it's less than six Sigma, though.
0:05:35 > 0:05:37OK, we've now got a Spernak.
0:05:37 > 0:05:39It's got lots of stuff in it, but no point source.
0:05:41 > 0:05:45This feels almost like something from science fiction.
0:05:45 > 0:05:46Within seconds,
0:05:46 > 0:05:50Phil has more information about the location of the source.
0:05:50 > 0:05:53Did I hear it is in M31 now, the Andromeda galaxy?
0:05:53 > 0:05:56Yeah. So, the thing is M31's full of sources. So we...
0:05:56 > 0:05:59- It's enormous in the sky as well. - It is, which doesn't help.
0:05:59 > 0:06:01So we've found an object, which is a known object,
0:06:01 > 0:06:04which is that one there in this image.
0:06:04 > 0:06:07- So there's the core of M31 off here. - Right.- The issue is, is this
0:06:07 > 0:06:11just because that object is there, or has it suddenly got brighter?
0:06:11 > 0:06:14And for some reason, I'm not getting a brightness of this new source.
0:06:14 > 0:06:18The problem is the signal is very faint, and, what's more,
0:06:18 > 0:06:23it's buried in a galaxy chock-full of other sources of radiation.
0:06:23 > 0:06:25A sort of vague source. The automatic system
0:06:25 > 0:06:28didn't detect anything, but by eye, it looks like there might be.
0:06:28 > 0:06:32So they were trying to see if they could figure out what was going on.
0:06:32 > 0:06:34I'm assuming the answer was no to that.
0:06:34 > 0:06:36I haven't yet managed to get a...
0:06:36 > 0:06:38- I know why, it's cos... - No, that's not what I was asking.
0:06:38 > 0:06:41Well, I mean, we could say a possible burst if you want.
0:06:41 > 0:06:43I don't know what I want. I don't know.
0:06:43 > 0:06:46You're the BA, I'm going to leave this in your hands.
0:06:46 > 0:06:48No, give us a second. Let me just think.
0:06:51 > 0:06:52After more discussion,
0:06:52 > 0:06:56Phil and Kim decide the trigger probably wasn't a GRB,
0:06:56 > 0:07:00but instead came from some other source within the Andromeda galaxy.
0:07:03 > 0:07:05So, Kim, what just happened?
0:07:05 > 0:07:10So, Swift triggered on something. We slewed round rapidly.
0:07:10 > 0:07:14We were on target in 74 seconds, so just over a minute.
0:07:14 > 0:07:18- That's impressive!- It then went on and showed us that not only have
0:07:18 > 0:07:23we detected one known source, we've detected five known sources.
0:07:23 > 0:07:27So it took us about 45 minutes on that telecon.
0:07:27 > 0:07:32If it had been a real GRB, yeah, probably more like 15, 20 minutes.
0:07:33 > 0:07:35So the satellite is back to its normal job,
0:07:35 > 0:07:38- and we're back to waiting for a burst?- Exactly.
0:07:40 > 0:07:43A few hours later, the story changes again,
0:07:43 > 0:07:46when Phil and Kim call the American team with their report.
0:07:48 > 0:07:52Yeah, Jamie, this is Phil. Can I just mention this morning's event?
0:07:52 > 0:07:55Because there's a couple of queries about it.
0:07:55 > 0:07:59They've noticed that the same telltale signal was also seen by
0:07:59 > 0:08:01a second telescope, called Fermi.
0:08:05 > 0:08:09More pressure now on Kim and Phil to come up with an explanation.
0:08:31 > 0:08:32Well, that was exciting.
0:08:32 > 0:08:35It turns out, while the team here were running about this morning,
0:08:35 > 0:08:38the Fermi gamma ray burst-hunting satellite also saw something.
0:08:38 > 0:08:41And so the fact that there was something seen by Swift and Fermi
0:08:41 > 0:08:43means it's worth going back for another look.
0:08:43 > 0:08:46So that's what the spacecraft's doing right now.
0:08:49 > 0:08:50For the next few hours,
0:08:50 > 0:08:55Kim and Phil are back observing M31, and reconsidering their data.
0:08:55 > 0:08:57Continue monitoring this variable AGN
0:08:57 > 0:09:03to get a good optical and X-ray... optical to X-ray SED.
0:09:03 > 0:09:05And later, they have a new theory.
0:09:06 > 0:09:07After running the numbers,
0:09:07 > 0:09:11they still believe that what they saw it isn't a gamma ray burst.
0:09:11 > 0:09:15They think it's an unusual object, bright in X-rays,
0:09:15 > 0:09:16that's actually been seen before.
0:09:18 > 0:09:23The object is called Swift J0243.6+6124.
0:09:23 > 0:09:27Really sticks in the mind. It's named after the position in the sky.
0:09:27 > 0:09:31So this was first detected by Swift on the third of October.
0:09:31 > 0:09:35We had a trigger, and we didn't know if it was a new gamma ray burst
0:09:35 > 0:09:37or a galactic transient.
0:09:37 > 0:09:41So we kept collecting data, and the X-rays stayed bright.
0:09:41 > 0:09:46Now, for a GRB, the X-rays, the afterglow and the X-rays will fade,
0:09:46 > 0:09:48fairly quickly over time.
0:09:48 > 0:09:51The fact that they stayed bright told us it wasn't a GRB,
0:09:51 > 0:09:52and it was some kind of transient.
0:09:52 > 0:09:56So it's still getting brighter at the moment, so we may trigger again.
0:09:56 > 0:09:58We'll just have to wait and see.
0:09:59 > 0:10:02Kim's day is over by 7pm.
0:10:02 > 0:10:05Any new activity now will come direct to her phone,
0:10:05 > 0:10:07and she'll have to deal with it at home.
0:10:08 > 0:10:11Which is of course exactly what happened next -
0:10:11 > 0:10:16a genuine gamma ray burst was detected at 12.07am.
0:10:18 > 0:10:22So, just after midnight, on the early hours of Saturday,
0:10:22 > 0:10:25- Swift triggered on a GRB.- So, what do we know about this burst?
0:10:25 > 0:10:27It's a long gamma ray burst,
0:10:27 > 0:10:30so this means it was a very massive star originally
0:10:30 > 0:10:33- more than 40 times the mass of our sun -
0:10:33 > 0:10:35and it just got to the end of its life.
0:10:35 > 0:10:37So at that point, it all collapses in on itself.
0:10:37 > 0:10:40And, as it does this, stars rotate, generally,
0:10:40 > 0:10:43so everything's spiralling round in, and you get jets of material
0:10:43 > 0:10:46shot out, and if those jets are pointing towards us,
0:10:46 > 0:10:51Swift can detect it, and that's what we see as a GRB.
0:10:51 > 0:10:56I can see now just how pressurised observing transient events is.
0:10:56 > 0:11:00And it makes sense, because with something that's over so quickly,
0:11:00 > 0:11:02decisions have to be made fast,
0:11:02 > 0:11:04and often on the basis of incomplete data.
0:11:10 > 0:11:13Gamma ray bursts are not the only transitory event in space, though.
0:11:14 > 0:11:19Recently, astronomers have observed a new type of phenomena,
0:11:19 > 0:11:22shorter, more powerful, and incredibly elusive...
0:11:25 > 0:11:26..fast radio bursts.
0:11:28 > 0:11:31Unlike anything else known,
0:11:31 > 0:11:36these strange chirps of radio waves are only milliseconds long,
0:11:36 > 0:11:38and have a unique characteristic sound,
0:11:38 > 0:11:43sweeping from high to low frequency, and their wavelength is
0:11:43 > 0:11:47at least a billion times longer than gamma ray bursts,
0:11:47 > 0:11:51suggesting that they may arise from a different cosmic process.
0:11:52 > 0:11:54But what?
0:11:56 > 0:11:58I spoke to Ben Stappers at Jodrell Bank,
0:11:58 > 0:12:02one of the UK's key research centres for fast radio bursts,
0:12:02 > 0:12:05to find out more about this incredibly strange phenomena.
0:12:08 > 0:12:11So, Ben, what are the FRBs, these fast radio bursts?
0:12:11 > 0:12:14Fast radio bursts are these very short duration,
0:12:14 > 0:12:18just a few milliseconds, of radio emission that are detected
0:12:18 > 0:12:21from far away by radio telescopes.
0:12:21 > 0:12:23So, how many others have been detected?
0:12:23 > 0:12:24I think around about 30 so far.
0:12:24 > 0:12:27But, you know, we're discovering a few every month now.
0:12:27 > 0:12:31- So, are there any other variations between them?- Yes, so we think
0:12:31 > 0:12:35that the vast majority of them so far have never been seen to repeat,
0:12:35 > 0:12:40even with observations of many, many hundreds of hours, in fact.
0:12:40 > 0:12:43But then, in 2012, the Arecibo telescope in Puerto Rico
0:12:43 > 0:12:48observed a fast radio burst that did something totally unexpected.
0:12:51 > 0:12:56There was a second FRB from the same source, and then more.
0:12:57 > 0:13:01Suddenly, this meant we had a chance to see an FRB happening
0:13:01 > 0:13:03in real time.
0:13:04 > 0:13:08One of the advantages of something that repeats is that we can
0:13:08 > 0:13:11actually go back and do more observing,
0:13:11 > 0:13:14and it's been possible for people to localise this burst.
0:13:14 > 0:13:18And what I mean by that is you can see exactly where it is in the sky,
0:13:18 > 0:13:21and associate it with a host galaxy.
0:13:21 > 0:13:24So it brings us to the million-dollar question -
0:13:24 > 0:13:25what actually are they?
0:13:25 > 0:13:28A lot of people have been having a lot of fun coming up with theories
0:13:28 > 0:13:31of what these things are. Presently, there are more theories
0:13:31 > 0:13:32than there are bursts. There's two...
0:13:32 > 0:13:35If we think that there are now two classes of these objects,
0:13:35 > 0:13:37where the repeater is maybe one type and those bursts we have
0:13:37 > 0:13:39only detected once are another type,
0:13:39 > 0:13:42the single ones might be associated with something cataclysmic,
0:13:42 > 0:13:46where the object itself is destroyed or the event is a one-off, so
0:13:46 > 0:13:50it could be something like merging neutron stars that are recurring.
0:13:50 > 0:13:54And there is also an idea that you have this thing called a blitzar,
0:13:54 > 0:13:57which is actually a very rapidly rotating neutron star.
0:13:57 > 0:14:01It's very massive, more massive than neutron stars should be,
0:14:01 > 0:14:04and eventually, as it slows down, it collapses into a black hole.
0:14:04 > 0:14:08And when that happens, it actually ejects its magnetic field,
0:14:08 > 0:14:10- and these sound very exotic. - It does, yes.
0:14:10 > 0:14:12In the case of the repeater,
0:14:12 > 0:14:15maybe it's a newly-born object called a magnetar.
0:14:15 > 0:14:19Now, a magnetar is also a neutron star, something that is spinning,
0:14:19 > 0:14:22that has a very large and very strong magnetic field.
0:14:22 > 0:14:27And so the idea is that maybe, in the birth event of these things,
0:14:27 > 0:14:29something happens that generates these fast radio bursts.
0:14:29 > 0:14:33Well, it's fantastic to hear about a genuine astronomical mystery,
0:14:33 > 0:14:36and I'd love to come back as you get more information and really find out
0:14:36 > 0:14:39- what they are.- Yes. I hope we can invite you back, and be to tell you
0:14:39 > 0:14:41- exactly what they are. - That's been fascinating.
0:14:41 > 0:14:43- Thank you so much. - Thank you.
0:14:50 > 0:14:54What's particularly exciting about this new fast response astronomy
0:14:54 > 0:14:58is that these powerful transitory events don't just occur
0:14:58 > 0:15:00in deep space. They happen in our solar system, too.
0:15:01 > 0:15:03Just think about our sun.
0:15:05 > 0:15:08The sun feels as though it hardly changes at all.
0:15:10 > 0:15:12But, actually, if we look close enough,
0:15:12 > 0:15:14we see a very different story.
0:15:16 > 0:15:20Lucie Green explains how the sun is actually a treasure trove
0:15:20 > 0:15:22of spectacular transient events.
0:15:25 > 0:15:28We all feel familiar with our local star.
0:15:28 > 0:15:31At 93 million miles away, the sun is still able to give us
0:15:31 > 0:15:35all the heat and the light that we need to survive, and today,
0:15:35 > 0:15:38it looks absolutely glorious in this beautiful sunny sky.
0:15:38 > 0:15:43But to really see the sun, we actually have to go inside.
0:15:45 > 0:15:48Because the best way to see what's happening on the sun
0:15:48 > 0:15:50is to look at it from space.
0:15:52 > 0:15:57And here it is - the sun as seen by Nasa's Solar Dynamics Observatory.
0:15:57 > 0:15:59It's a telescope in orbit around the earth.
0:15:59 > 0:16:03These images are just a few minutes old,
0:16:03 > 0:16:07and they show, not only an enormous range of structure,
0:16:07 > 0:16:10but also just how dynamic the sun is.
0:16:10 > 0:16:14And, for example, over here, we see these beautiful
0:16:14 > 0:16:18evolving glowing arches of gas in the sun's atmosphere.
0:16:18 > 0:16:21And it turns out that these structures are actually key
0:16:21 > 0:16:24to understanding the entire sun.
0:16:26 > 0:16:27Because they are shaped,
0:16:27 > 0:16:31like everything else in the atmosphere of the sun, by magnetism.
0:16:33 > 0:16:38The inside of the sun is a swirling mass of electrically charged gas,
0:16:38 > 0:16:41and wherever you have moving charged particles,
0:16:41 > 0:16:43you have a magnetic field.
0:16:43 > 0:16:46And the thing I really love about magnetic fields is that they have
0:16:46 > 0:16:49an influence on the material, or the stuff, that's around them.
0:16:49 > 0:16:53To show that, I have some iron filings suspended in fluid,
0:16:53 > 0:16:55and a bar magnet.
0:16:55 > 0:16:59And if I put the magnet on the iron filings, they immediately respond,
0:16:59 > 0:17:02and they take on these beautiful, arch-like shapes
0:17:02 > 0:17:06as they follow the lines of force of the magnetic field,
0:17:06 > 0:17:08running from the north pole to the south pole.
0:17:10 > 0:17:14And in the same way that the iron filings responded to my magnet,
0:17:14 > 0:17:18the gases in the sun's atmosphere respond to the sun's magnetic field.
0:17:18 > 0:17:22So, here you can see these giant arches of gas in the atmosphere.
0:17:22 > 0:17:24Oh, look at that, there was a plasma flow shooting along
0:17:24 > 0:17:27these magnetic field structures.
0:17:27 > 0:17:31Now, underneath this arch-like structure is something that we call
0:17:31 > 0:17:34a prominence or a filament - they are exactly the same thing.
0:17:34 > 0:17:38This is relatively cooled plasma lofted into the atmosphere
0:17:38 > 0:17:40of the sun by its magnetic field.
0:17:40 > 0:17:43But just look how it's moving -
0:17:43 > 0:17:46it's sort of shimmering and oscillating.
0:17:46 > 0:17:50Now, studying these plasma clouds isn't just an academic activity.
0:17:50 > 0:17:53They actually mean something for us here on the Earth as well,
0:17:53 > 0:17:57because occasionally they will erupt into the solar system.
0:17:59 > 0:18:02This is an eruption that happened just a few days ago.
0:18:02 > 0:18:04There is a filament structure here,
0:18:04 > 0:18:06and it erupts out into the solar system.
0:18:06 > 0:18:08Now, to give you...
0:18:08 > 0:18:11Here it goes! So there goes the eruption.
0:18:11 > 0:18:12And it is an enormous structure.
0:18:12 > 0:18:15To give you a sense of scale, the Earth is about as big
0:18:15 > 0:18:19as this bright patch in the atmosphere of the sun here.
0:18:19 > 0:18:22So this eruption starts off already many times the size of the Earth,
0:18:22 > 0:18:25and then expands to become many, many times bigger
0:18:25 > 0:18:28actually than the sun itself. And now you can see
0:18:28 > 0:18:32that enormous structure heading out into the solar system.
0:18:35 > 0:18:38And, if these eruptions are Earth-directed,
0:18:38 > 0:18:40they slam into the Earth's magnetic field,
0:18:40 > 0:18:44shaking it up and triggering what we call stormy space weather,
0:18:44 > 0:18:48affecting our electricity networks, our high-frequency radio
0:18:48 > 0:18:52communications, all kinds of ways our modern technologies
0:18:52 > 0:18:54are ultimately affected by these eruptions from the sun.
0:18:57 > 0:19:00The last transient phenomenon that I want to show you
0:19:00 > 0:19:03is something called spicules, and here we are.
0:19:03 > 0:19:06All along the edge of the sun are spicules.
0:19:06 > 0:19:11You can see these dark, sort of like grass-like features,
0:19:11 > 0:19:14or like the spines on a hedgehog, but waving in the wind,
0:19:14 > 0:19:18and they are the spicules. They are as tall as the Earth is wide,
0:19:18 > 0:19:22and they really are transient features, because they only last
0:19:22 > 0:19:25on the sun for around 10 to 15 minutes. Today,
0:19:25 > 0:19:29they're viewed as being important in heating the corona of the sun.
0:19:29 > 0:19:34They transport gas from the lower layers to the upper atmosphere,
0:19:34 > 0:19:38the corona, which has a temperature of millions of degrees Kelvin,
0:19:38 > 0:19:40or millions of degrees Celsius.
0:19:42 > 0:19:46Ironically, this part of the sun is an area astronomers consider
0:19:46 > 0:19:51relatively tranquil, and they call it the quiet sun.
0:19:51 > 0:19:55But images like this from the Solar Dynamics Observatory have shown us
0:19:55 > 0:19:58that this isn't really the quiet sun at all.
0:19:58 > 0:20:01The quiet sun, in a sense, is dominated by all this activity.
0:20:05 > 0:20:08Observing this transient solar behaviour
0:20:08 > 0:20:10is not just for professionals.
0:20:12 > 0:20:15Amateurs can relatively easily spot
0:20:15 > 0:20:17many of the phenomena that Lucie saw.
0:20:18 > 0:20:20Pete Lawrence explains.
0:20:21 > 0:20:25The sun is one of the most rewarding objects in the whole sky.
0:20:26 > 0:20:29But first, a word of caution, because looking at the sun
0:20:29 > 0:20:33under any circumstances can be extremely dangerous.
0:20:33 > 0:20:36It's very bright, and it can permanently damage your eyes
0:20:36 > 0:20:40or equipment. So, if you intend to use a telescope,
0:20:40 > 0:20:44you need to use a certified solar filter,
0:20:44 > 0:20:46because that will reduce the incoming light to a safe level.
0:20:48 > 0:20:52And remember to remove or cap your telescope's finder.
0:20:52 > 0:20:55Apart from the fact that it too could be damaged, the temptation
0:20:55 > 0:20:59to look through it could end with disastrous consequences.
0:20:59 > 0:21:00Line the telescope up with the sun
0:21:00 > 0:21:04whilst looking at the telescope's shadow.
0:21:04 > 0:21:06That way, you won't look into the sun's glare.
0:21:10 > 0:21:12So, once you're lined up, you can start viewing,
0:21:12 > 0:21:16and the most obvious transit solar phenomenon is sun spots.
0:21:18 > 0:21:22These are caused by intense magnetic fields creating localised cooling.
0:21:23 > 0:21:27The result is a region that looks darker than its hot surroundings.
0:21:30 > 0:21:33Through my white light filter, I can see there is just one tiny sunspot
0:21:33 > 0:21:37on view, but other days you can get more sun spots visible.
0:21:37 > 0:21:40But to see the really fast-moving action,
0:21:40 > 0:21:43I need to switch to a different type of filter - a hydrogen alpha filter.
0:21:46 > 0:21:50An H-alpha filter rejects all the wavelengths of visible light,
0:21:50 > 0:21:53except those given off by excited hydrogen atoms.
0:21:57 > 0:21:59Now I've got the hydrogen alpha filter fitted,
0:21:59 > 0:22:02I've got some incredible detail on the sun's disc.
0:22:02 > 0:22:03I can see some dark filaments
0:22:03 > 0:22:07- that's cool clouds of hydrogen in the sun's atmosphere -
0:22:07 > 0:22:09but the really impressive stuff is down at the bottom of the disc
0:22:09 > 0:22:14I've got here, because if I go down there and then boost the exposure,
0:22:14 > 0:22:19I can see some incredible prominences on the edge of the sun.
0:22:20 > 0:22:24So, remember - astronomy can be just as rewarding in the daytime
0:22:24 > 0:22:27as at night. But if you're going to get to know the sun,
0:22:27 > 0:22:29do make sure you observe it safely.
0:22:35 > 0:22:40Observing brief cosmic events isn't only redefining how we do astronomy,
0:22:40 > 0:22:44it's also giving us new information about the universe.
0:22:46 > 0:22:49Which brings us back to that neutron star collision
0:22:49 > 0:22:51that made the headlines last month.
0:22:52 > 0:22:56Just as we were preparing to make this programme, news broke of
0:22:56 > 0:23:00an exciting new transient of a type that we simply haven't seen before.
0:23:01 > 0:23:04Tonight at ten, an international team of scientists has discovered
0:23:04 > 0:23:09the effects of a collision between dead stars, called neutron stars,
0:23:09 > 0:23:11which happened 130 million years ago.
0:23:14 > 0:23:19The first sign was a gravitational wave picked up by the huge detectors
0:23:19 > 0:23:22at Ligo in America and Virgo in Italy.
0:23:24 > 0:23:28At almost exactly the same time, the Fermi satellite
0:23:28 > 0:23:32detected a gamma ray burst coming from the same location.
0:23:32 > 0:23:36It's the first time that those two things - gravitational waves
0:23:36 > 0:23:39and a burst of light - have been seen coming from the same place.
0:23:40 > 0:23:44This detection triggered a secondary flurry of activity of
0:23:44 > 0:23:47other telescopes right around the world, including Swift,
0:23:47 > 0:23:50all scouring the sky for more information.
0:23:52 > 0:23:56All the evidence suggested that what had been seen was the collision of
0:23:56 > 0:24:01two neutron stars, the compressed cores of now dead massive stars,
0:24:01 > 0:24:05now ripped apart in an event of unimaginable violence.
0:24:07 > 0:24:09This turned out to be a kilonova,
0:24:09 > 0:24:13one of the biggest and most powerful explosions known.
0:24:23 > 0:24:25As well as being burst advocate on Swift,
0:24:25 > 0:24:29Phil Evans headed up Swift's observations of the kilanova.
0:24:29 > 0:24:32I persuaded him to leave his desk for a moment to explain
0:24:32 > 0:24:36what really happened, and how this event helps us understand
0:24:36 > 0:24:39how heavy elements are actually created.
0:24:41 > 0:24:44- So, this is a very exciting event. - Yes.- So, what did you see?
0:24:44 > 0:24:47Well, we didn't see X-rays, which was a surprise.
0:24:47 > 0:24:50Because if you have a gamma ray burst, you normally,
0:24:50 > 0:24:51not always, but normally get X-rays.
0:24:51 > 0:24:54And with this thing being so close, it should have been about
0:24:54 > 0:24:5712,000 times brighter than a typical gamma ray burst.
0:24:57 > 0:24:59So we were expecting something.
0:24:59 > 0:25:02We did see very bright ultraviolet emission.
0:25:02 > 0:25:06And that was a real surprise, because if there's no X-rays,
0:25:06 > 0:25:08then where did the ultraviolet emission come from?
0:25:08 > 0:25:09There's no afterglow.
0:25:09 > 0:25:12And this is what led us to the belief that maybe what we'd found
0:25:12 > 0:25:15was not a typical gamma ray burst afterglow, but something new.
0:25:15 > 0:25:19So, people assume that this thing is what's called a kilanova.
0:25:19 > 0:25:21- That's right. - These two neutron stars merging.
0:25:21 > 0:25:23And they have this unusual signature.
0:25:23 > 0:25:27Why does two neutron stars colliding produce light anyway?
0:25:27 > 0:25:29Why do we see it as a gamma ray burst, and where does
0:25:29 > 0:25:32- the ultraviolet come from? - When you get two neutron stars...
0:25:32 > 0:25:35Now, remember, these have got very, very strong gravity.
0:25:35 > 0:25:39You've got the mass of the sun, and gravity is proportional to mass,
0:25:39 > 0:25:43but crammed down into an area maybe 10km across.
0:25:43 > 0:25:46So the size of the city we're standing in right now, for example.
0:25:46 > 0:25:49So when you make the radius really small, gravity shoots up.
0:25:49 > 0:25:51So you get two neutron stars really close together,
0:25:51 > 0:25:53and they start off looking sort of round, and then they start
0:25:53 > 0:25:56to distort, almost becoming teardrop shaped, because each one is
0:25:56 > 0:25:58pulling really hard on the nearby side of the other one,
0:25:58 > 0:26:00and less hard on the other side.
0:26:00 > 0:26:04And that changing gravity across the neutron star is enough to start
0:26:04 > 0:26:06to distort it, and then eventually, to rip it apart.
0:26:06 > 0:26:08So as it falls in, it gives off radiation,
0:26:08 > 0:26:13and we think that in a lot of events where you get stuff falling in,
0:26:13 > 0:26:17it's spiralling round in a disc, and as it falls in, you launch jets.
0:26:17 > 0:26:19So you get material that is blasted out,
0:26:19 > 0:26:23the sort of the poles of the event, very close to the speed of light.
0:26:23 > 0:26:26But in a kilanova, you're seeing something very special, because
0:26:26 > 0:26:29as well as this material that is falling in and coming out in jets,
0:26:29 > 0:26:31you've got loads of material swilling round
0:26:31 > 0:26:35- very, very dense material - close together, full of neutrons.
0:26:35 > 0:26:37So, this is neutron star rubble?
0:26:37 > 0:26:40Neutron star rubble, right. And it's neutron rich.
0:26:40 > 0:26:43And this makes it a prime site for something that we call
0:26:43 > 0:26:46the rapid neutron capture process. And this is basically one of
0:26:46 > 0:26:49the ways the universe can create elements heavier than iron.
0:26:49 > 0:26:53But when you do that, you make unstable elements, and they decay.
0:26:53 > 0:26:56Because, you know, just like your uranium in
0:26:56 > 0:26:59your nuclear power station does, it decays, and that glows.
0:26:59 > 0:27:03And so that gives us what we call the kilanova, and it's
0:27:03 > 0:27:06the signature of the formation of heavy elements in the universe.
0:27:06 > 0:27:09So, your bright ultraviolet light that Swift was seeing
0:27:09 > 0:27:13from this event might come from the decay of new elements that
0:27:13 > 0:27:16- are being created.- That's right.- And now we know when it comes from.
0:27:16 > 0:27:18Now we know at least where some of it comes from.
0:27:18 > 0:27:21And we only know that because we saw this ultraviolet flash of light.
0:27:31 > 0:27:34What all this shows is something very exciting.
0:27:37 > 0:27:40We can now actually watch the universe change
0:27:40 > 0:27:42in front of our eyes.
0:27:50 > 0:27:54And these events that happen in just seconds
0:27:54 > 0:27:56can have profound consequences.
0:27:59 > 0:28:01That's it for this programme,
0:28:01 > 0:28:03from here at Jodrell Bank, and also from Swift.
0:28:03 > 0:28:06But do join us again next month, when we're presenting our
0:28:06 > 0:28:09Christmas special, getting back to basics to show everybody how
0:28:09 > 0:28:13to enjoy the night sky, including how to get started in astronomy,
0:28:13 > 0:28:16the best equipment to buy, and also how to enjoy the night sky
0:28:16 > 0:28:19with no tech at all. Do go to our website in the meantime,
0:28:19 > 0:28:21and check out Pete's star guide,
0:28:21 > 0:28:24and also great stuff we couldn't fit into this programme.
0:28:24 > 0:28:29In the meantime, of course, get outside, and get looking up.
0:28:29 > 0:28:30Goodnight.