1 00:00:03,320 --> 00:00:06,000 ETHEREAL MUSIC 2 00:00:06,000 --> 00:00:08,360 DR MAGGIE ADERIN-POCOCK: This is one of 3 00:00:08,360 --> 00:00:10,480 the most famous photographs in astronomy - 4 00:00:10,480 --> 00:00:13,080 the so-called Pillars of Creation. 5 00:00:16,680 --> 00:00:20,640 These vast clouds of gas and dust are in the Eagle Nebula. 6 00:00:23,200 --> 00:00:26,000 PROFESSOR CHRIS LINTOTT: Pillars of Creation is an apt name - 7 00:00:26,000 --> 00:00:29,960 nebulae play a key role in the life cycle of stars, 8 00:00:29,960 --> 00:00:32,240 they're there at their birth and at their death. 9 00:00:34,840 --> 00:00:37,760 And so tonight, The Sky At Night investigates 10 00:00:37,760 --> 00:00:41,440 what makes these delicate clouds the crucibles of creation. 11 00:00:47,200 --> 00:00:51,120 MUSIC: At the Castle Gate from Pelleas et Melisande by Sibelius 12 00:01:12,560 --> 00:01:15,680 Today we've come to the University of London Observatory, 13 00:01:15,680 --> 00:01:17,760 where scientists have watched 14 00:01:17,760 --> 00:01:21,280 many of the magnificent processes that sculpt nebulae. 15 00:01:21,280 --> 00:01:24,400 Despite being beside a noisy and rather well-lit A1, 16 00:01:24,400 --> 00:01:28,680 some of the most dramatic nebula can be seen from right here. 17 00:01:29,880 --> 00:01:33,880 Coming up, what triggers these spectacular clouds to collapse 18 00:01:33,880 --> 00:01:37,040 and give birth to new stars? 19 00:01:37,040 --> 00:01:40,000 And how the process turns full circle 20 00:01:40,000 --> 00:01:42,920 as dying stars create new nebulae. 21 00:01:42,920 --> 00:01:44,480 Plus, 22 00:01:44,480 --> 00:01:48,200 Andrea Sella reveals the surprising chemistry that takes place 23 00:01:48,200 --> 00:01:52,960 inside these interstellar clouds, creating ingredients for new stars. 24 00:01:54,360 --> 00:01:55,840 For me as a chemist, 25 00:01:55,840 --> 00:01:59,240 the idea of chemical reactions happening in this environment 26 00:01:59,240 --> 00:02:02,080 seems almost impossible. 27 00:02:02,080 --> 00:02:05,120 But that turns out not to be the case at all. 28 00:02:05,120 --> 00:02:09,600 And Peter's here with his guide to the best nebulae to see this month 29 00:02:09,600 --> 00:02:11,200 and how to photograph them. 30 00:02:15,080 --> 00:02:16,880 So let's take a closer look at 31 00:02:16,880 --> 00:02:19,360 that image that we saw just a few minutes ago - 32 00:02:19,360 --> 00:02:21,720 the magnificent Pillars of Creation. 33 00:02:21,720 --> 00:02:26,200 The image is from 1995 - taken with the Hubble Space Telescope - 34 00:02:26,200 --> 00:02:29,320 and it's a mosaic, which accounts for the strange jagged shape. 35 00:02:29,320 --> 00:02:31,600 But what we should really concentrate on 36 00:02:31,600 --> 00:02:34,440 are the magnificent structures that it reveals. 37 00:02:34,440 --> 00:02:37,760 I think this picture really captures people's imagination 38 00:02:37,760 --> 00:02:40,400 because it's what we expect to see out there in the heavens - 39 00:02:40,400 --> 00:02:43,200 wondrous beauty on a really epic scale. 40 00:02:44,800 --> 00:02:46,920 And it truly is epic. 41 00:02:46,920 --> 00:02:50,280 Those tiny, finger-like protrusions on the top of the columns 42 00:02:50,280 --> 00:02:55,200 are in fact larger than the whole of our solar system. 43 00:02:55,200 --> 00:02:59,000 But in the beauty there is also science. 44 00:02:59,000 --> 00:03:02,160 These vast columns of dust and gas, known as elephant trunks, 45 00:03:02,160 --> 00:03:04,200 are the home of star formation. 46 00:03:04,200 --> 00:03:07,480 And it just goes to show the vital role that nebulae play 47 00:03:07,480 --> 00:03:10,120 in the life cycle of stars. 48 00:03:12,200 --> 00:03:17,440 This is a process that happens in nebulae all over the universe. 49 00:03:17,440 --> 00:03:19,880 But we can see it in action here 50 00:03:19,880 --> 00:03:22,120 because of the way the nebula is lit. 51 00:03:25,120 --> 00:03:27,960 The Eagle Nebula, which forms the backdrop to the pillars, 52 00:03:27,960 --> 00:03:29,200 is an emission nebula, 53 00:03:29,200 --> 00:03:32,160 which means the light comes from hot, glowing gas. 54 00:03:32,160 --> 00:03:34,520 And the different colours that you can see 55 00:03:34,520 --> 00:03:37,760 represent emission from different elements in the nebula. 56 00:03:37,760 --> 00:03:41,240 But the real action here is in the pillars themselves. 57 00:03:41,240 --> 00:03:44,480 And to take a look at that, we need to switch to the infrared. 58 00:03:44,480 --> 00:03:47,040 And in this image from the Herschel Observatory 59 00:03:47,040 --> 00:03:48,560 that's exactly what you can see - 60 00:03:48,560 --> 00:03:53,240 the cold gas and dust in the pillars ready to collapse and form stars. 61 00:03:53,240 --> 00:03:56,440 Although we know that stars are born in nebulae, 62 00:03:56,440 --> 00:03:59,080 the details of that process remain a mystery. 63 00:03:59,080 --> 00:04:02,080 But what is becoming clear is that one key factor 64 00:04:02,080 --> 00:04:04,920 is the extraordinary chemistry that takes place - 65 00:04:04,920 --> 00:04:07,520 reactions that simply shouldn't be happening. 66 00:04:09,040 --> 00:04:11,760 Chemist Andrea Sella is finding out more 67 00:04:11,760 --> 00:04:14,960 about why chemical reactions are so unexpected in space, 68 00:04:14,960 --> 00:04:19,400 and what role this remarkable chemistry plays in star formation. 69 00:04:19,400 --> 00:04:23,480 As a chemist, I see my field as the study of matter 70 00:04:23,480 --> 00:04:26,320 and the way in which it can be transformed. 71 00:04:26,320 --> 00:04:29,560 We look at the way atoms come together to form molecules 72 00:04:29,560 --> 00:04:31,800 and the way in which those molecules interact. 73 00:04:34,240 --> 00:04:37,600 But chemical reactions usually need certain conditions 74 00:04:37,600 --> 00:04:39,040 in order to take place. 75 00:04:39,040 --> 00:04:43,600 Conditions that are common here on Earth but not in space. 76 00:04:45,800 --> 00:04:47,840 I've set up some experiments here in the lab, 77 00:04:47,840 --> 00:04:50,520 to demonstrate some of these factors. 78 00:04:52,120 --> 00:04:54,800 So the first key factor is actually temperature. 79 00:04:54,800 --> 00:04:58,720 I'm going to illustrate this with these two colourless solutions 80 00:04:58,720 --> 00:05:01,240 that I'm going to mix together at room temperature. 81 00:05:03,080 --> 00:05:06,920 And when I do that, you can see that actually not very much happens. 82 00:05:06,920 --> 00:05:11,240 But if in fact I move this onto a hot plate, the molecules, 83 00:05:11,240 --> 00:05:12,840 because they're getting hotter, 84 00:05:12,840 --> 00:05:15,480 they start to move faster, they collide more violently, 85 00:05:15,480 --> 00:05:18,760 and the result is they're more likely to react. 86 00:05:18,760 --> 00:05:21,160 And look, it's already gone. 87 00:05:21,160 --> 00:05:25,200 If, on the other hand, we took this reaction and put it on ice, 88 00:05:25,200 --> 00:05:28,640 then everything would become really sluggish and slow 89 00:05:28,640 --> 00:05:31,360 and the reaction would take much longer. 90 00:05:32,920 --> 00:05:37,600 The trouble is heat is a rare commodity out in deep space, 91 00:05:37,600 --> 00:05:40,000 where the temperature is close to absolute zero. 92 00:05:42,360 --> 00:05:45,920 And temperature isn't the only consideration. 93 00:05:45,920 --> 00:05:49,200 So the second factor that controls a chemical reaction 94 00:05:49,200 --> 00:05:51,640 is actually the concentration. In other words, 95 00:05:51,640 --> 00:05:56,760 how many molecules we actually pack into a given volume of our solution. 96 00:05:56,760 --> 00:05:59,760 I've got exactly the same set-up we had before, 97 00:05:59,760 --> 00:06:03,800 but what I've done is I've actually increased one of the concentrations. 98 00:06:03,800 --> 00:06:05,480 And when I mix them together... 99 00:06:07,040 --> 00:06:09,920 ..the reaction goes instantaneously. 100 00:06:09,920 --> 00:06:13,560 So having molecules crammed in close together 101 00:06:13,560 --> 00:06:17,000 makes these collisions much more likely. 102 00:06:17,000 --> 00:06:20,680 And this presents a real problem in the emptiness of space, 103 00:06:20,680 --> 00:06:23,520 where the chance of one atom encountering another 104 00:06:23,520 --> 00:06:25,520 is infinitesimally small. 105 00:06:27,360 --> 00:06:30,440 Even in a nebula the material is so spread out 106 00:06:30,440 --> 00:06:34,280 and so diffuse, that if we imagine one atom to be the size of 107 00:06:34,280 --> 00:06:39,560 this penny in London, the next atom is way off somewhere in Manchester. 108 00:06:45,800 --> 00:06:49,520 And there's something else we can take advantage of in a lab. 109 00:06:50,960 --> 00:06:53,760 We can add a catalyst to encourage a reaction. 110 00:06:55,120 --> 00:06:58,280 So in this flask I've got some methanol - an alcohol - 111 00:06:58,280 --> 00:07:00,960 along with, of course, oxygen from the air. 112 00:07:00,960 --> 00:07:04,160 And there isn't really very much going on. 113 00:07:04,160 --> 00:07:08,440 But if I take a little bit of this platinum wire 114 00:07:08,440 --> 00:07:11,600 and I place it inside the flask... 115 00:07:11,600 --> 00:07:14,800 then something interesting is going to happen. 116 00:07:14,800 --> 00:07:18,160 Now, before we put the platinum in, the methanol 117 00:07:18,160 --> 00:07:20,800 and the oxygen weren't reacting. 118 00:07:20,800 --> 00:07:23,120 But now that the platinum is actually in there, 119 00:07:23,120 --> 00:07:25,120 the methanol lands on the surface, 120 00:07:25,120 --> 00:07:28,680 the oxygen lands on the surface and they start to react. 121 00:07:28,680 --> 00:07:31,520 And notice that what this does is it raises the temperature. 122 00:07:31,520 --> 00:07:34,360 The platinum is beginning to glow and the reaction is going 123 00:07:34,360 --> 00:07:38,400 faster and faster until, eventually, it all gets so hot... 124 00:07:38,400 --> 00:07:39,760 POP 125 00:07:39,760 --> 00:07:42,000 ..the vapour itself ignites and goes pop. 126 00:07:43,560 --> 00:07:45,920 But none of these phenomena we find in the lab 127 00:07:45,920 --> 00:07:49,680 are the kind of things we'd expect to find in deep space. 128 00:07:51,160 --> 00:07:54,920 So for me as a chemist, the idea of chemical reactions 129 00:07:54,920 --> 00:07:58,400 happening in this environment seems almost impossible. 130 00:07:58,400 --> 00:08:02,160 But that turns out not to be the case at all. 131 00:08:04,080 --> 00:08:08,000 Scientists know that there are in fact many complex chemical reactions 132 00:08:08,000 --> 00:08:13,400 taking place within nebulae despite the seemingly hopeless conditions. 133 00:08:13,400 --> 00:08:16,960 Not only that, they're a crucial part of the process by which 134 00:08:16,960 --> 00:08:19,360 stars and planets are formed. 135 00:08:19,360 --> 00:08:22,040 ..The thing which I think is funny are the echoes... 136 00:08:22,040 --> 00:08:25,560 'Cosmochemist Steve Price attempts to recreate these reactions 137 00:08:25,560 --> 00:08:27,720 'in a vacuum chamber right here in his lab.' 138 00:08:29,080 --> 00:08:30,800 So, Steve, what's the evidence 139 00:08:30,800 --> 00:08:33,960 for the idea that there's chemistry actually in nebulae? 140 00:08:33,960 --> 00:08:38,040 Well, we can actually see the molecules by observing 141 00:08:38,040 --> 00:08:39,720 the light that they emit. 142 00:08:39,720 --> 00:08:43,280 We can see from the atoms that we've got to start with, 143 00:08:43,280 --> 00:08:46,760 we must be doing chemistry to make molecules like molecular hydrogen. 144 00:08:46,760 --> 00:08:49,880 But making hydrogen, surely that's trivial?! 145 00:08:49,880 --> 00:08:53,040 It's just taking two hydrogen atoms 146 00:08:53,040 --> 00:08:56,880 and combining them together to make an H2 molecule. 147 00:08:56,880 --> 00:08:59,760 Isn't that the simplest thing you could...? Why is that interesting? 148 00:08:59,760 --> 00:09:02,200 Because you think about doing the chemistry on Earth, 149 00:09:02,200 --> 00:09:03,280 where it is very easy. 150 00:09:03,280 --> 00:09:06,280 But in nebula we've got very low pressures - 151 00:09:06,280 --> 00:09:09,600 so the H atoms don't encounter each other very often at all. 152 00:09:09,600 --> 00:09:13,440 And it's very cold - so they don't hit each other very hard. 153 00:09:13,440 --> 00:09:17,040 But also, they can fall apart very easily. 154 00:09:17,040 --> 00:09:20,440 We need something to actually bring the H atoms together, 155 00:09:20,440 --> 00:09:23,960 to help them react and actually form that H2 molecule. 156 00:09:25,200 --> 00:09:28,920 Luckily nebulae aren't just vast clouds of gas, 157 00:09:28,920 --> 00:09:32,440 they're also full of microscopic dust particles. 158 00:09:32,440 --> 00:09:35,040 And it's these dust particles 159 00:09:35,040 --> 00:09:36,760 that are key to forming new molecules. 160 00:09:36,760 --> 00:09:40,360 So, what's the role of these dust grains? 161 00:09:40,360 --> 00:09:42,160 Well, the dust grains allow us 162 00:09:42,160 --> 00:09:45,600 to bring the atoms of hydrogen together to form H2. 163 00:09:45,600 --> 00:09:47,880 The atoms stick on the surface of the dust grains, 164 00:09:47,880 --> 00:09:50,120 they run around and find each other, 165 00:09:50,120 --> 00:09:53,560 and that enables them to form H2 much more efficiently 166 00:09:53,560 --> 00:09:55,600 than they would out in the gas phase. 167 00:09:55,600 --> 00:09:58,440 So you're really talking about a catalyst, 168 00:09:58,440 --> 00:10:01,440 a bit like the platinum surface that we saw earlier. 169 00:10:01,440 --> 00:10:03,240 Exactly like that, yeah. 170 00:10:03,240 --> 00:10:05,800 Without the dust grain, the atoms wouldn't really 171 00:10:05,800 --> 00:10:08,360 encounter each other for long enough to make H2. 172 00:10:08,360 --> 00:10:10,320 So it's vital in bringing them together 173 00:10:10,320 --> 00:10:12,040 and making the reaction happen. 174 00:10:12,040 --> 00:10:14,680 So, yeah, it's a catalyst. And so what do they look like? 175 00:10:14,680 --> 00:10:18,160 We think the dust is rough. And here's a picture 176 00:10:18,160 --> 00:10:21,360 of some simulated dust grains that people have made in the laboratory. 177 00:10:21,360 --> 00:10:23,480 And you can see they're nothing like your nice, 178 00:10:23,480 --> 00:10:25,320 flat plateau of carbon. They're horrible. 179 00:10:25,320 --> 00:10:27,720 I think they're pretty. They look like cauliflower. 180 00:10:27,720 --> 00:10:30,520 What you can see straightaway is its textured and fluffy surface 181 00:10:30,520 --> 00:10:34,440 is perhaps important for trapping molecules on the surface. 182 00:10:34,440 --> 00:10:37,640 So the structure of the dust is really quite important. 183 00:10:37,640 --> 00:10:40,480 Now, we've talked about the formation of hydrogen molecules, 184 00:10:40,480 --> 00:10:42,240 but what other things are out there? 185 00:10:42,240 --> 00:10:44,120 What other molecular species are there? 186 00:10:44,120 --> 00:10:45,800 There's an enormous number. 187 00:10:45,800 --> 00:10:49,720 We are almost up to 200 other species we've seen out there 188 00:10:49,720 --> 00:10:52,960 of these interstellar molecules. A huge range of things. 189 00:10:52,960 --> 00:10:55,000 Long carbon chains, 190 00:10:55,000 --> 00:10:57,760 things like methanol, ethanol. 191 00:10:57,760 --> 00:11:01,880 And trying to explain how you form these very complicated molecules 192 00:11:01,880 --> 00:11:06,680 in these very extreme conditions of low temperature, low pressures, 193 00:11:06,680 --> 00:11:09,400 where you don't collide very often, has been a real challenge. 194 00:11:09,400 --> 00:11:13,840 And a lot of the molecules are formed by unusual gas-phase chemistry. 195 00:11:13,840 --> 00:11:18,760 But for many of them, water, methanol, we also need to say 196 00:11:18,760 --> 00:11:22,440 that things are being formed on the dust grain surfaces as well. 197 00:11:22,440 --> 00:11:25,960 So, why are molecules so important inside nebulae? 198 00:11:25,960 --> 00:11:28,160 One of the things that these dust clouds 199 00:11:28,160 --> 00:11:31,280 in the nebula do is they collapse, and in the end they form stars. 200 00:11:31,280 --> 00:11:36,360 But for that collapse we need to lose energy from the molecules 201 00:11:36,360 --> 00:11:38,680 to actually slow them down to let them collapse. 202 00:11:38,680 --> 00:11:40,800 And you need molecules to do that. 203 00:11:40,800 --> 00:11:45,960 The molecules get energised in collisions, but then emit light, 204 00:11:45,960 --> 00:11:48,720 and that light then goes away from the nebula 205 00:11:48,720 --> 00:11:50,560 and you've lost some energy. 206 00:11:50,560 --> 00:11:53,320 So that allows the cloud to collapse and cool. 207 00:11:53,320 --> 00:11:55,600 So chemistry's vital in making the molecules 208 00:11:55,600 --> 00:11:57,520 which are vital in forming the stars. 209 00:11:57,520 --> 00:12:00,440 So chemistry really lies at the heart of star formation. 210 00:12:00,440 --> 00:12:03,200 Yeah, we couldn't form stars without the molecules 211 00:12:03,200 --> 00:12:05,960 and we need chemistry to form the molecules. Absolutely. 212 00:12:12,080 --> 00:12:15,560 Nebulae provide the perfect environment for star formation 213 00:12:15,560 --> 00:12:19,640 but the processes that trigger this formation are shrouded in mystery. 214 00:12:19,640 --> 00:12:23,080 Chris is investigating the inner workings of nebulae 215 00:12:23,080 --> 00:12:25,720 with star formation expert Serena Viti. 216 00:12:25,720 --> 00:12:27,600 I always love talking about star formation 217 00:12:27,600 --> 00:12:29,920 because it's a problem that gets more complicated 218 00:12:29,920 --> 00:12:31,200 the more you know about it. 219 00:12:31,200 --> 00:12:32,840 It's the basics I've understood. 220 00:12:32,840 --> 00:12:34,680 We've got to get something to collapse, 221 00:12:34,680 --> 00:12:37,200 but we don't understand the detail of how that happens. 222 00:12:37,200 --> 00:12:40,640 So, what do we know? Do we know where stars form, for example? 223 00:12:40,640 --> 00:12:45,320 We do know the stars form from dark molecular clouds. 224 00:12:45,320 --> 00:12:48,080 We've got a picture of one of those cores here. 225 00:12:48,080 --> 00:12:52,760 So what are we seeing here? This is 68. 226 00:12:52,760 --> 00:12:55,120 It's a dark core, very cold - 227 00:12:55,120 --> 00:12:57,200 about 10 Kelvin 228 00:12:57,200 --> 00:13:00,480 or minus 250 degrees Celsius, or something like that - 229 00:13:00,480 --> 00:13:04,080 and it's about a third of a light-year across. 230 00:13:04,080 --> 00:13:09,600 And this core may start forming a star because of gravity. 231 00:13:09,600 --> 00:13:13,280 So gravity will take over and collapse will happen. 232 00:13:13,280 --> 00:13:17,240 So it's important that it's dark because that allows it to be cool. 233 00:13:17,240 --> 00:13:18,720 That's right. 234 00:13:18,720 --> 00:13:21,920 It seems strange to be talking about the temperature affecting gravity. 235 00:13:21,920 --> 00:13:26,240 If a gas is not cold, then the atoms and molecules 236 00:13:26,240 --> 00:13:28,240 in this gas will start moving 237 00:13:28,240 --> 00:13:31,440 faster and faster as the temperature increases. 238 00:13:31,440 --> 00:13:35,080 If they move faster and faster, then gravity cannot take over 239 00:13:35,080 --> 00:13:37,200 and the gas cannot collapse. OK. 240 00:13:37,200 --> 00:13:39,360 So that's why the molecules are important, then? 241 00:13:39,360 --> 00:13:42,640 Yes, because the molecules allow the gas to cool. 242 00:13:42,640 --> 00:13:46,960 So molecules radiate away the heat from the cloud 243 00:13:46,960 --> 00:13:51,600 and the temperature will be low enough for gravity to take over 244 00:13:51,600 --> 00:13:53,840 and you have a runaway effect. 245 00:13:53,840 --> 00:13:56,080 Eventually, right at the centre of this core, 246 00:13:56,080 --> 00:13:59,320 you will have a very dense and very hot core, 247 00:13:59,320 --> 00:14:01,360 which we call the protostar. 248 00:14:01,360 --> 00:14:03,760 I think we've got one of these here. Yes, here we go. 249 00:14:03,760 --> 00:14:05,640 So this is L1157. 250 00:14:05,640 --> 00:14:09,280 This is an infrared image from the Spitzer Satellite Telescope. 251 00:14:09,280 --> 00:14:15,440 This blob of gas is very hot and nuclear fusion will have started. 252 00:14:15,440 --> 00:14:18,240 And due to the high pressure in this core, 253 00:14:18,240 --> 00:14:22,440 you start seeing these jets of gas coming out. 254 00:14:22,440 --> 00:14:24,960 We've got an image here from Herschel. 255 00:14:24,960 --> 00:14:27,760 So, what are we looking at here? 256 00:14:27,760 --> 00:14:30,800 These are filaments of gas and dust 257 00:14:30,800 --> 00:14:34,240 and you can see the star's forming inside the filaments. 258 00:14:34,240 --> 00:14:37,480 And what this is telling you is that stars 259 00:14:37,480 --> 00:14:42,400 don't necessarily form from round, well-defined cores. 260 00:14:42,400 --> 00:14:45,280 What does that mean? What does that tell us about the process? 261 00:14:45,280 --> 00:14:48,000 Well, they tell us that the giant molecular clouds, 262 00:14:48,000 --> 00:14:52,760 when they fragment, when they're made in different forms, 263 00:14:52,760 --> 00:14:54,640 filaments, cores, 264 00:14:54,640 --> 00:14:57,080 that's all to do probably with turbulence. 265 00:14:57,080 --> 00:14:58,200 We still don't know 266 00:14:58,200 --> 00:15:00,680 where this turbulence comes from in the first place. 267 00:15:00,680 --> 00:15:03,880 But something stirred them up. Something stirred them up, yes. 268 00:15:03,880 --> 00:15:06,560 Interesting. And what are the big unknowns in this field? 269 00:15:06,560 --> 00:15:08,920 What don't we know about star formation? 270 00:15:08,920 --> 00:15:12,280 Well, we certainly don't know where turbulence comes from, for a start. 271 00:15:12,280 --> 00:15:16,320 We also don't know how the most massive stars, 272 00:15:16,320 --> 00:15:20,440 stars much larger than our sun, how they actually form 273 00:15:20,440 --> 00:15:22,400 because the process of star formation there 274 00:15:22,400 --> 00:15:23,840 it is not so well understood. 275 00:15:23,840 --> 00:15:27,280 Due to the initial mass of the cloud, 276 00:15:27,280 --> 00:15:29,560 the collapse must happen very quickly. 277 00:15:29,560 --> 00:15:32,800 Because gravity is more important if you've got more stuff. That's right. 278 00:15:32,800 --> 00:15:36,120 We'd expect that with so much mass, the star's falling, 279 00:15:36,120 --> 00:15:38,680 then the heat would be so high 280 00:15:38,680 --> 00:15:44,240 the pressure should kick-start, basically, equilibrium. 281 00:15:44,240 --> 00:15:47,040 You should stop gravity. 282 00:15:47,040 --> 00:15:50,120 You quickly reach a stage where you can have a protostar 283 00:15:50,120 --> 00:15:52,360 and all of this other stuff, but... 284 00:15:52,360 --> 00:15:55,600 Before you build up mass in the centre to get to these massive stars 285 00:15:55,600 --> 00:15:58,040 and yet we know that these massive stars exist. 286 00:15:58,040 --> 00:16:01,160 There are several theories out there on how these massive stars 287 00:16:01,160 --> 00:16:05,600 can form, but the jury is still out. Interesting. 288 00:16:05,600 --> 00:16:07,520 Well, come back and tell us when you find out. 289 00:16:13,760 --> 00:16:16,800 You might think that to capture astonishing images of nebulae, 290 00:16:16,800 --> 00:16:20,520 you need a multi-billion-dollar space telescope. 291 00:16:20,520 --> 00:16:22,840 But that is definitely not the case at all. 292 00:16:24,320 --> 00:16:25,400 Yeah, this is just a... 293 00:16:25,400 --> 00:16:28,320 Pete's gone to meet members of the Newbury Astronomical Society, 294 00:16:28,320 --> 00:16:32,680 to see what they've photographed from right here on Earth. 295 00:16:32,680 --> 00:16:36,240 Ah, that's beautiful. M27, the Dumbbell Nebula. Oh, yeah. 296 00:16:36,240 --> 00:16:39,640 This is taken from four 45 second subframes. 297 00:16:39,640 --> 00:16:42,720 The subframe is a fancy way of saying the exposure. One exposure. 298 00:16:42,720 --> 00:16:44,840 That's a pretty good job though, I have to say. 299 00:16:44,840 --> 00:16:47,520 There's lots of beautiful detail in there and you can just... 300 00:16:47,520 --> 00:16:50,600 There's a little threesome of stars there, right in the centre. 301 00:16:50,600 --> 00:16:52,480 If you can split those, 302 00:16:52,480 --> 00:16:54,640 that's supposed to be the mark of a good dumbbell. 303 00:16:54,640 --> 00:16:56,240 Oh, gosh. So well done. 304 00:16:56,240 --> 00:16:58,920 I'll take credit for that one. Thank you very much. Thanks, Pete. 305 00:16:58,920 --> 00:17:00,880 John, I think you've got one of - 306 00:17:00,880 --> 00:17:04,280 there it is - the more exotic nebulae in the winter skies. 307 00:17:04,280 --> 00:17:07,440 Yeah, M1, the Crab Nebula. That's a brilliant picture. 308 00:17:07,440 --> 00:17:09,640 It's actually my first attempt 309 00:17:09,640 --> 00:17:13,480 at what we call an LRGB image, taken with a black-and-white camera 310 00:17:13,480 --> 00:17:15,520 through a red filter, green filter, blue filter. 311 00:17:15,520 --> 00:17:18,000 It's worked really well because you've got that lovely colour 312 00:17:18,000 --> 00:17:20,960 in the background, but you've also pulled out all the filaments. 313 00:17:20,960 --> 00:17:24,600 It looks like an exploded star. Which is exactly what it is. 314 00:17:24,600 --> 00:17:25,880 It's a supernova remnant. 315 00:17:25,880 --> 00:17:28,240 One of the stars in the centre there is the pulsar - 316 00:17:28,240 --> 00:17:30,680 the neutron star which drives it. Do you know which one? 317 00:17:30,680 --> 00:17:32,560 It's one of those pair and for the life of me 318 00:17:32,560 --> 00:17:34,040 I can't remember which one it is. 319 00:17:34,040 --> 00:17:36,680 I remember looking at this when I was at university actually, 320 00:17:36,680 --> 00:17:39,400 and we looked at various pictures of it taken many years apart, 321 00:17:39,400 --> 00:17:41,760 and you can see the expansion of the gas. Yes. 322 00:17:41,760 --> 00:17:44,480 So there's another record which you could put against that 323 00:17:44,480 --> 00:17:45,800 and see how much it's grown. 324 00:17:45,800 --> 00:17:47,480 Isn't that incredible? 325 00:17:47,480 --> 00:17:49,520 Perhaps I'll take another in ten years' time. 326 00:17:49,520 --> 00:17:51,000 A brilliant result. Well done. 327 00:17:54,280 --> 00:17:58,080 So how can you go about imaging nebulae too? 328 00:17:58,080 --> 00:18:00,200 I've got some simple tips. 329 00:18:00,200 --> 00:18:03,040 Starting with where to view them from. 330 00:18:05,920 --> 00:18:08,160 Nebulae are fantastic objects to look at. 331 00:18:08,160 --> 00:18:11,720 But unlike stars, which are point objects in the night sky, 332 00:18:11,720 --> 00:18:13,840 nebulae are diffuse. 333 00:18:13,840 --> 00:18:15,840 And to get the best possible views of them, 334 00:18:15,840 --> 00:18:18,240 you need to get to a site which is really, really dark 335 00:18:18,240 --> 00:18:20,560 and doesn't suffer from too much light pollution. 336 00:18:22,480 --> 00:18:24,240 You can get a surprisingly good view 337 00:18:24,240 --> 00:18:26,480 through a pair of binoculars or a telescope. 338 00:18:27,880 --> 00:18:29,480 And one of the best to start with 339 00:18:29,480 --> 00:18:32,440 is the Orion Nebula because it's so bright. 340 00:18:33,560 --> 00:18:35,880 When you think of an image of a nebula, 341 00:18:35,880 --> 00:18:39,000 you probably think of something which is bright and colourful. 342 00:18:39,000 --> 00:18:41,280 But actually when you look at one of these objects 343 00:18:41,280 --> 00:18:43,520 through the eyepiece of a telescope, 344 00:18:43,520 --> 00:18:46,760 what you'll see is something rather grey and smudge like. 345 00:18:46,760 --> 00:18:50,440 But the longer you look, the more detail you'll see. 346 00:18:50,440 --> 00:18:53,240 And when you look at a bright nebula, like for example 347 00:18:53,240 --> 00:18:56,560 the Orion Nebula, you can actually start to make out some colour. 348 00:18:56,560 --> 00:19:00,160 It's possible to see, for example, a greenish hue to it. 349 00:19:00,160 --> 00:19:03,800 Now that's given off by oxygen atoms which are excited 350 00:19:03,800 --> 00:19:05,440 and they give off a wavelength 351 00:19:05,440 --> 00:19:09,280 which is in the most sensitive part of the visual range of our eyes. 352 00:19:10,480 --> 00:19:12,200 But to see the colours of nebulae 353 00:19:12,200 --> 00:19:13,440 in all their glory, 354 00:19:13,440 --> 00:19:15,640 you need to turn to a camera. 355 00:19:16,960 --> 00:19:20,280 The best way to get a nice image of a nebula 356 00:19:20,280 --> 00:19:23,320 is to take a long exposure photograph. 357 00:19:23,320 --> 00:19:26,320 But if you're using a fixed platform like this tripod, 358 00:19:26,320 --> 00:19:28,760 the problem you've got is, if you take a long exposure, 359 00:19:28,760 --> 00:19:31,960 the Earth's rotation tends to make the nebula trail. 360 00:19:34,320 --> 00:19:37,760 A simple solution is to use a wide-angle lens, 361 00:19:37,760 --> 00:19:41,320 taking a short, 30 to 60 second, exposure. 362 00:19:41,320 --> 00:19:43,080 This should capture the nebula 363 00:19:43,080 --> 00:19:45,760 as a small, coloured patch. 364 00:19:45,760 --> 00:19:49,240 But to see real detail, you'll need a telescope. 365 00:19:49,240 --> 00:19:51,280 And for that, a tracking mount is essential. 366 00:19:54,040 --> 00:19:56,920 For details of some great nebula to look out for, 367 00:19:56,920 --> 00:20:00,400 here's my guide to what's up in this month's night sky. 368 00:20:02,240 --> 00:20:06,080 The Orion Nebula, M42, is big and bright 369 00:20:06,080 --> 00:20:07,960 and can be seen, with binoculars, 370 00:20:07,960 --> 00:20:10,640 sitting right at the centre of Orion's Sword. 371 00:20:11,920 --> 00:20:17,200 Above M42 is NGC 1977, the Running Man Nebula, 372 00:20:17,200 --> 00:20:19,800 so-called because long exposures of it 373 00:20:19,800 --> 00:20:22,560 show the silhouette of a running figure. 374 00:20:25,560 --> 00:20:29,120 The famous Horsehead Nebula hangs down from Alnitak, 375 00:20:29,120 --> 00:20:31,160 the eastern star in Orion's Belt. 376 00:20:33,000 --> 00:20:35,240 A large telescope is required to see it 377 00:20:35,240 --> 00:20:38,560 but the nebula can be picked out with modest imaging kit. 378 00:20:40,480 --> 00:20:45,680 The Flame Nebula, NGC 2024, also lies just east of Alnitak. 379 00:20:48,520 --> 00:20:49,960 The Pleiades open cluster 380 00:20:49,960 --> 00:20:52,720 is high in the sky before midnight during December. 381 00:20:54,760 --> 00:21:00,640 North of the Pleiades is NGC 1499, the California Nebula, 382 00:21:00,640 --> 00:21:02,560 a deep-red emission nebula 383 00:21:02,560 --> 00:21:04,480 in the constellation Perseus. 384 00:21:04,480 --> 00:21:06,160 And it's quite spectacular. 385 00:21:13,000 --> 00:21:15,840 We talked about how the clouds of gas and dust 386 00:21:15,840 --> 00:21:19,040 that make up nebulae can collapse to form new stars. 387 00:21:19,040 --> 00:21:21,960 But where did that material come from in the first place? 388 00:21:21,960 --> 00:21:25,920 Surprisingly, the answer is from other long-dead stars. 389 00:21:27,520 --> 00:21:30,080 When high-mass stars reach the end of their lives 390 00:21:30,080 --> 00:21:31,520 they explode... 391 00:21:33,840 --> 00:21:36,800 ..in an astonishing display that we call a supernova. 392 00:21:36,800 --> 00:21:39,160 And the debris that's left from these explosions 393 00:21:39,160 --> 00:21:41,240 becomes a type of nebula. 394 00:21:44,240 --> 00:21:46,320 Maggie is talking to Steve Fossey, 395 00:21:46,320 --> 00:21:50,440 who uses the telescopes here to find and to study these phenomena. 396 00:21:52,240 --> 00:21:56,800 On a cloudy day earlier this year, Steve, and some of his students, 397 00:21:56,800 --> 00:21:58,680 made an astonishing discovery. 398 00:21:58,680 --> 00:22:01,920 During a brief break in the clouds, 399 00:22:01,920 --> 00:22:04,880 they imaged M82, the cigar galaxy. 400 00:22:06,240 --> 00:22:10,480 And immediately it was clear that something was different. 401 00:22:10,480 --> 00:22:14,000 We took our image on January 21. And that's this image. 402 00:22:14,000 --> 00:22:15,400 That's this one here. 403 00:22:15,400 --> 00:22:19,600 This is a short exposure and under some cloudy sky, so it's bit grainy. 404 00:22:19,600 --> 00:22:21,840 But you can see there's a new object... 405 00:22:21,840 --> 00:22:23,600 This one here? That's right. 406 00:22:23,600 --> 00:22:27,240 ..on the bar of the galaxy that clearly wasn't there before. 407 00:22:27,240 --> 00:22:30,520 And I said to the students, "This is very unusual. 408 00:22:30,520 --> 00:22:33,640 "This potentially could be a supernova." 409 00:22:33,640 --> 00:22:35,480 It was a supernova. 410 00:22:35,480 --> 00:22:39,280 And soon it became clear it was a very special kind of supernova. 411 00:22:40,600 --> 00:22:42,400 By 6am the next morning, 412 00:22:42,400 --> 00:22:47,080 the spectrum which had been taken by a professional group at Paloma 413 00:22:47,080 --> 00:22:50,320 in California, using a telescope system in Arizona, 414 00:22:50,320 --> 00:22:52,680 had confirmed that it was a supernova. 415 00:22:52,680 --> 00:22:55,040 And in fact not just any old supernova, 416 00:22:55,040 --> 00:22:58,480 it was what we call a thermonuclear, or a type 1a supernova. 417 00:22:58,480 --> 00:23:00,160 Cos they're quite rare? 418 00:23:00,160 --> 00:23:01,480 Those type are rare. 419 00:23:01,480 --> 00:23:04,560 We think, on average, a supernova in a typical galaxy 420 00:23:04,560 --> 00:23:08,600 like the Milky Way, on average about once every hundred years. 421 00:23:08,600 --> 00:23:12,040 Those type, about twice a millennium... Oh, wow! 422 00:23:12,040 --> 00:23:14,760 ..in any given galaxy. 423 00:23:14,760 --> 00:23:18,560 So now, the supernova has exploded, so what was left behind? 424 00:23:18,560 --> 00:23:21,200 Sometimes you get black holes. Sometimes you get neutron stars. 425 00:23:21,200 --> 00:23:22,800 What was left behind with this one? 426 00:23:22,800 --> 00:23:24,440 Well, this type of explosion 427 00:23:24,440 --> 00:23:27,120 comes from something that we call a white dwarf. 428 00:23:27,120 --> 00:23:30,960 It's about the mass of the sun, but about the size of the Earth 429 00:23:30,960 --> 00:23:33,600 and it's the dead core of the star that was. 430 00:23:33,600 --> 00:23:36,120 And if this is in a binary star system, 431 00:23:36,120 --> 00:23:38,920 it can draw gas from the binary partner 432 00:23:38,920 --> 00:23:41,720 until it reaches a critical limit at which 433 00:23:41,720 --> 00:23:45,600 the temperature in the core rises to several hundred million degrees, 434 00:23:45,600 --> 00:23:47,600 the carbon atoms fuse together 435 00:23:47,600 --> 00:23:50,080 in a runaway thermonuclear explosion 436 00:23:50,080 --> 00:23:53,920 that blows the whole star apart in just a few seconds 437 00:23:53,920 --> 00:23:56,400 and there is nothing left behind. 438 00:23:56,400 --> 00:23:59,040 So, what happens to the envelope that's expanding outwards? 439 00:23:59,040 --> 00:24:01,920 So we have an expanding envelope of hot gas, 440 00:24:01,920 --> 00:24:05,120 the outer layers of which are moving at, say, about a 20th of 441 00:24:05,120 --> 00:24:08,560 the speed of light. So very, very rapid expansion. 442 00:24:08,560 --> 00:24:10,400 A hot bubble of gas. 443 00:24:10,400 --> 00:24:13,760 And we see these kinds of objects within our own galaxy. 444 00:24:13,760 --> 00:24:18,280 Things like this. So in this example here we have a supernova remnant. 445 00:24:18,280 --> 00:24:22,200 And this is the remains of actually a much more massive star 446 00:24:22,200 --> 00:24:26,240 which exploded we think about 30,000 years ago. 447 00:24:26,240 --> 00:24:29,400 And that shock wave has picked up hydrogen gas 448 00:24:29,400 --> 00:24:33,120 and other elements and swept them up into thin filaments 449 00:24:33,120 --> 00:24:35,800 to create this rather shell-like structure. 450 00:24:35,800 --> 00:24:38,440 So, will your supernova look like this, given time? 451 00:24:38,440 --> 00:24:41,840 Well, eventually, some other gases from the explosion 452 00:24:41,840 --> 00:24:44,160 will probably hit some of the surrounding 453 00:24:44,160 --> 00:24:46,800 circumstellar or interstellar material. 454 00:24:46,800 --> 00:24:49,680 We will never see it like this because it's so far away. 455 00:24:49,680 --> 00:24:51,240 What it may well do is, 456 00:24:51,240 --> 00:24:54,040 it may well glow in the radio part of the spectrum 457 00:24:54,040 --> 00:24:56,240 because it picks up electrons and they move 458 00:24:56,240 --> 00:24:58,320 so fast that they radiate energy 459 00:24:58,320 --> 00:25:00,840 in the radio part of the spectrum. 460 00:25:00,840 --> 00:25:03,160 Most of the supernova remnants in our galaxy 461 00:25:03,160 --> 00:25:06,000 have been discovered through radio observations. 462 00:25:06,000 --> 00:25:07,840 So the gas continues moving out. 463 00:25:07,840 --> 00:25:10,880 Does it just continue doing that until it disintegrates? 464 00:25:10,880 --> 00:25:12,160 Exactly. 465 00:25:12,160 --> 00:25:15,800 Eventually it will dissipate over some tens of thousands of years. 466 00:25:15,800 --> 00:25:17,680 Actually this is a process that has been 467 00:25:17,680 --> 00:25:20,880 going on in the Milky Way for billions of years. 468 00:25:20,880 --> 00:25:23,680 Supernova remnants which have come and gone. 469 00:25:23,680 --> 00:25:27,080 I think of the Milky Way as like a giant recycling unit. 470 00:25:27,080 --> 00:25:30,600 And so supernovae, like the one in Messier 82, 471 00:25:30,600 --> 00:25:33,840 will produce new elements and dust grains as well, 472 00:25:33,840 --> 00:25:36,520 which are so important for new star formation. 473 00:25:36,520 --> 00:25:40,480 So this supernova remnant compresses the clouds 474 00:25:40,480 --> 00:25:42,440 and it stirs up the interstellar gas 475 00:25:42,440 --> 00:25:46,880 creating turbulence, which then leads to the formation of new 476 00:25:46,880 --> 00:25:49,120 and complex filaments within those clouds 477 00:25:49,120 --> 00:25:51,000 from which new stars are formed. 478 00:25:51,000 --> 00:25:53,920 So it provides the pressure for the star formation to start? 479 00:25:53,920 --> 00:25:55,120 Exactly. 480 00:25:55,120 --> 00:25:58,400 It provides the pressure in the interstellar gas 481 00:25:58,400 --> 00:26:00,600 to trigger new star formation. 482 00:26:00,600 --> 00:26:03,480 That's fantastic. Thank you so much, Steve. It's been brilliant. 483 00:26:09,000 --> 00:26:11,640 We couldn't let this episode pass without updating you 484 00:26:11,640 --> 00:26:15,520 on the status of Philae, everyone's favourite comet bouncing lander. 485 00:26:15,520 --> 00:26:19,280 It's still dormant on the surface of comet Churyumov-Gerasimenko 486 00:26:19,280 --> 00:26:21,960 but we have had some exciting news here on the ground. 487 00:26:21,960 --> 00:26:25,680 Firstly, the search for Philae on the comet's surface continues. 488 00:26:25,680 --> 00:26:28,280 ROMAP, the magnetometer on-board Philae, 489 00:26:28,280 --> 00:26:31,120 has got some more information which is indicated. 490 00:26:31,120 --> 00:26:34,280 But after the first bounce, the second bounce caused Philae 491 00:26:34,280 --> 00:26:37,000 to actually drag one of its feet in the surface 492 00:26:37,000 --> 00:26:38,960 and it's caused it to tumble. 493 00:26:38,960 --> 00:26:42,360 Now we've also got an image of where we think the landing is likely to be. 494 00:26:42,360 --> 00:26:44,480 We've two potential landing sites. 495 00:26:44,480 --> 00:26:46,320 We've got that long strip there 496 00:26:46,320 --> 00:26:47,880 and also the green spot. 497 00:26:47,880 --> 00:26:49,320 We think that it might have been 498 00:26:49,320 --> 00:26:50,600 in either of these positions, 499 00:26:50,600 --> 00:26:53,480 but it very much depends on the topography of the surface. 500 00:26:53,480 --> 00:26:56,040 In either case, it is where we thought it was, 501 00:26:56,040 --> 00:26:58,080 on the edge of this crater-like feature. 502 00:26:58,080 --> 00:27:00,120 But we've found a new way of visualising this. 503 00:27:00,120 --> 00:27:02,560 So this is the first image that we got from the surface. 504 00:27:02,560 --> 00:27:04,640 There's the legs sitting down 505 00:27:04,640 --> 00:27:07,680 and these bouldery crater walls in the background. 506 00:27:07,680 --> 00:27:10,480 An image-processing expert called Mattias Malmer 507 00:27:10,480 --> 00:27:13,120 has processed this image, made a guess as to the distances, 508 00:27:13,120 --> 00:27:15,280 and created this visualisation. 509 00:27:15,280 --> 00:27:18,240 Don't be distracted by the colours, they're exaggerated, 510 00:27:18,240 --> 00:27:22,120 but this gives you a real sense of depth and you get a sense of 511 00:27:22,120 --> 00:27:24,360 Philae clinging on on the edge of the cliff. 512 00:27:24,360 --> 00:27:26,920 If you look at that and then go back to the original image, 513 00:27:26,920 --> 00:27:30,720 you understand where it is, on the edge of this quite precarious pit. 514 00:27:30,720 --> 00:27:33,560 It looks like a pretty craggy surface, doesn't it? It does. 515 00:27:33,560 --> 00:27:36,280 Speaking of the surface, both Ptolemy and COSAC, 516 00:27:36,280 --> 00:27:39,040 the on-board chemical analysers on the Philae, 517 00:27:39,040 --> 00:27:40,680 have detected organic molecules. 518 00:27:40,680 --> 00:27:41,800 This is really exciting. 519 00:27:41,800 --> 00:27:43,720 We sort of expected to see something there, 520 00:27:43,720 --> 00:27:46,680 but I'm really looking forward to finding out exactly what they are. 521 00:27:48,400 --> 00:27:52,440 And finally, given the time of year, 522 00:27:52,440 --> 00:27:54,800 we couldn't end the programme without a look at this - 523 00:27:54,800 --> 00:27:57,600 the very festive Christmas Tree cluster 524 00:27:57,600 --> 00:28:00,200 set against the background of an emission nebula. 525 00:28:02,280 --> 00:28:03,640 That's it for this month, 526 00:28:03,640 --> 00:28:05,320 but when we come back next month 527 00:28:05,320 --> 00:28:06,720 we'll be investigating Gaia - 528 00:28:06,720 --> 00:28:09,480 the remarkable mission that's set to transform 529 00:28:09,480 --> 00:28:11,520 our view of the Milky Way galaxy. 530 00:28:11,520 --> 00:28:12,680 We'll be looking at 531 00:28:12,680 --> 00:28:15,320 the billion pixel sensor at the heart of this mission 532 00:28:15,320 --> 00:28:18,560 and discovering how YOUR images can help verify its results. 533 00:28:18,560 --> 00:28:21,680 So, in the meantime, get outside and get looking up. 534 00:28:21,680 --> 00:28:23,400 Good night. 535 00:28:23,400 --> 00:28:27,000 MUSIC: At the Castle Gate from Pelleas et Melisande by Sibelius