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this is a thing called a merge Cube which is a way of visualizing three-dimensional objects in a way that you can interact with them through augmented reality so we can look at the Crab Nebula in a way that we've never been able to before thanks to some new data cool isn't it well yeah we'll come back to in a minute okay just quickly remind us what the Crab Nebula is a supernova Remnant it's somewhat unusual as an astronomical object in that we know when it was created because the Chinese astronomers recorded its appearance in 1054 CE and for the last Almost Thousand Years the that Supernova explosion has been expanding out so what we see today is the remnant of the explosions isn't that beautiful yeah but actually
it's missing a big part of the story right because this is a two-dimensional picture and obviously this is you know you can sort of tell just by looking at it this is intrinsically a three-dimensional structure that we're sort of not really able to see just because irritatingly we only view the universe from One Direction but fortunately a paper came along just a couple of years ago by Thomas Martin and his collaborators which says 3D mapping of the Crab Nebula is Sitel which is basically was looking at the Crab Nebula and reconstructing its three-dimensional structure they actually exploit the fact that it was an explosion and if you think about what happens in an explosion everything flies apart from everything else and so in the
case of the crowd nebula that's you know almost a thousand years ago it blew up it's been expanding ever since but not everything flies out at quite the same speed in a typical explosion some bits going a bit faster some bits are going a bit slower and the bits that have got further this by now are the bits that are going fastest and that means that when you sort of have a view through the Crab Nebula you're looking at different bits of the explosion some of which are coming towards you some of which are going away from you and the bits which are going fastest are the bits which you've got furthest either fastest towards you or fastest away from you and then as you go further and further in
you're looking at Material which is traveling more and more slowly because it hasn't got so far that means On Any Given sort of line of sight through the Crab Nebula you're seeing all this material but some of it with the bit that's coming towards you the fastest is the bit that telling you where the front of the nebula is and so on all the way through to the back where the bit that's going away from you is traveling fast is and the nice thing in astronomy is we can measure that speed along the line of sight because there are Doppler shifts in the spectral line so you have these discrete colors that come out due to the atoms that the Crab Nebula is made up of so for example it's primarily hydrogen
so we see these bright emission lines so spikes of emission at very particular colors due to hydrogen gas but if the bits are traveling away from you that bit will be redshifted it will be Doppler shifted a little bit towards the red end of the spectrum if it's coming towards you it'll be shifted a little bit towards the blue end of the spectrum so that means that along any given line of sight you can pick out different components of this explosion by the adopter shift the bits that are coming towards you the fastest will be the most redshifted and so on all the way through to the back end so if that means you can map out the gas all the way along the line of sight now if you then did the
same thing everywhere across the face of the Crab Nebula you could actually map out that full three-dimensional structure Not only would you know where the gas was on the plane of the sky but you'd also know where it was along the line of sight through the Crab Nebula through the stopless shift and that's exactly what these guys did they mapped out the whole of the Crab Nebula so it's about 300 000 individual Spectra across the face of the Crab Nebula um that allowed them to reconstruct its full three-dimensional shape Professor this doesn't sound dissimilar to what you do with galaxies you look at the Doppler shift of stars to figure out is that star going away from me or towards
me it's the same idea but of course in general in a star that Doppler shift doesn't tell you anything about where the star is along the line of sight the fact that a star is coming towards you doesn't tell you it's in front of the Galaxy or behind the Galaxy it's a kind of a unique property of an explosion that there's a direct translation between how fast the stuff's traveling and where it is along that line of sight I can show you what their data looks like yeah so there's a few of the figures from that paper and the figure at the top just shows you what these spikes of emission at different wavelengths look like you plot a spectrum is you can have that how much light there is versus what wavelength
you're looking at so these individual little color bands that are telling you what the gas is made of chiropra's spikes in this that's useful in itself because that tells you what the gas is made of and even things like what temperature it is there's lots of information in just that Spectrum this is kind of a template of what they're what they expect to see for a single blob of gas this below is the actual data that they're getting so you can see it's a bit noisier because you never get perfect data but they were able to pick out this fingerprint twice in this particular spectrum that they had turned one of which is slightly blue shifted and the other which is slightly redshifting so you can see you've got
this set of three and a set of two and you can see there are two sets of those that are conveniently colored blue and orange here and so this is telling us that along this particular line of sight there are two blobs of gas one of them happens to be coming towards us the other happens to be going away from us and by the amount that it shifted we can actually tell where in the explosion that is so how much they're traveling towards us is telling you how far in front of the center it is and vice versa for the redshifted bit and then the one at the bottom is just showing that actually sometimes you get many more than two components so this is one is slightly ratchier because the little
blobs are clearly a bit fainter but they are actually able to pick out four distinct components in this particular case Professor I can see how that helps you with coming towards you and going away from you how does this help with going to the left and going to the right so that you get just by repeating the process all across the face of the Crab Nebula so each one of the Spectra tells you where things are along the line of sight but then you have to repeat that time and time again to get the entire face of the Crab Nebula now they use this fancy spectrograph called Sitel which actually does that all in one go it's a thing called an Imaging spectrograph it basically means they get
a Spectra of the whole of the Crab Nebula with a single set of observations rather than having to repeat them individually to get all the Spectrum all right so every single Clump within reason is now got a sort of a X Y and Z coordinate yep so this is where I got bit involved in the project because I've always been interested in making three-dimensional images of things quick plug for one of my 3D models so there we go I sell these little glass cubes this one for example is a redshift survey showing the positions of hundreds of thousands of galaxies so I got kind of interested in how you represent astronomical data particularly three-dimensional astronomical data so here's our galaxy if I'd known you were
coming to film might have polished them up a bit you don't run this business anymore by the way I do no but one of my colleagues does so yeah here we go here's the Hubble Space Telescope anything you want in three dimensions there you go that's Saturn with its rings astronomically accurate Rings here we go gratuitous plug okay all right so you're already interested I'm very interested in it but actually I'm also interested in more interactive ways that you can actually get this data and actually you know make it more widely available um and I sort of got interested in this bit of Technology which is a thing called a merge Cube which a company in the US makes for basically doing augmented reality in the classroom using it for educational
purposes um and so I got quite interested in this idea of putting astronomical data into the kind of augmented reality that this enables and this Crab Nebula data set seemed too good an opportunity to miss so I talked to the people who made the observations they're very happy to share it um and in fact we've made a glass cube of it but I've also wanted to uh see how what it would look like in this sort of augmented reality space so this is what the cube looks like when we view it with the augmented reality software so we really can pick up the Crab Nebula turn it around see what it looks like from different directions so for example you can see that the Crab Nebula isn't round it's actually
heart-shaped which is rather sweet but also if we turn it around and view it end on you start seeing a kind of a ring-like structure around the outside and that's telling you that there's a sort of hollow shell of material that there's almost an evacuated Center and there's a big shell of material which is expanding which appears as kind of a ring when you view it on the plane of the sky where's the view that we see somewhere around there I think I've got some of the holes in the right places anyway yeah it looks like that's something yeah that look that I'm kind of trying to match it up to the picture here yeah something like that what have you learned besides that it's heartache it's not enough if that is not
how cute is that it has it taught us something about Supernova we didn't know before so one of the interesting things they found when they started analyzing these data and you can actually see in this if I zoom in it in a bit as you can see there's this rather intricate structure almost a kind of honeycomb structure of bits which are kind of there are exact almost hexagonal voids or hexagonal rings of enhanced material and it turns out that's that was sort of not terribly well known before this observation was made and there is an explanation for it which is that it's thought one of the things that happens in the Supernova is you make lots of hairy elements the whole process is so
energetic that you end up creating lots of the heavy elements that actually you know we see around us in the world today but quite a lot of those heavy elements are radioactive they're radioactively unstable and one thing that gets made in great abundance which is radioactively unstable is nickel and what it's thought that's happened the reason why you end up with that sort of honeycomb structure of voids is that there are plumes of this radioactive nickel that get kind of thrown out in the explosion as that nickel radioactively decays it heats the gas and that heated gas then expands which kind of squishes the gas around it and so those sort of honeycomb structures you see are where that radioactive nickel has expanded and
compressed all the other gas up into these fine filamentary structures so it's actually telling us something about the properties of the explosion when you start studying the kind of the explosion Remnant it tells you quite important things about how the explosion happened and what the process was that's kind of got frozen in uh and we can still see it in that Remnant today the other little bit of the story which I sort of skated over a bit is there's a bit left over from the Supernova which is a neutron star and in fact this is one of those rotating neutron stars that you see as a pulsar something which kind of pulses its radiation so people have studied that quite a lot but the Pulsar
itself is continuing to heat the gas around it so there's very hot gas in that cavity inside the Supernova explosion so there are other aspects to the story as well but the story of the explosion itself is kind of written into what we can study in that expanded remnant seven wonders of the Milky Way The Crab Nebula would be one of them at the moment from where we're sitting yes if we were the other side of the Galaxy we might have a different set of Wonders but actually it was one of the Glorious things you can see in the sky you should do the seven wonders of the Milky Way that'd be a good one wouldn't it yeah so I'll show you the glass cubes oh yeah I think I've got it here yeah this is what it looks like
it's pretty cool very nice Link in the description light of different colors gets bent by different amounts the bright Arc that you're seeing in the image that you took is actually where the light from the sun is coming in at sort of an oblique angle it goes in through the top and then out through the side but each time it goes through one of those surfaces the path of the light gets bent a bit because it's passing from one medium air to another medium ice
