1 00:00:02,360 --> 00:00:05,320 2016 will be remembered for many different reasons. 2 00:00:05,320 --> 00:00:07,320 Brexit means Brexit... 3 00:00:07,320 --> 00:00:10,960 But whatever you thought of the events of this year, 4 00:00:10,960 --> 00:00:13,240 one thing is certain - 5 00:00:13,240 --> 00:00:15,960 it has been one of the most extraordinary years 6 00:00:15,960 --> 00:00:18,200 in space exploration. 7 00:00:18,200 --> 00:00:21,000 Scientists are hailing a major discovery... 8 00:00:21,000 --> 00:00:23,160 We have detected... 9 00:00:23,160 --> 00:00:25,840 gravitational waves. We did it. 10 00:00:25,840 --> 00:00:27,440 CHEERING AND APPLAUSE 11 00:00:27,440 --> 00:00:30,360 We have a spacecraft in orbit around Jupiter, 12 00:00:30,360 --> 00:00:32,400 and I think people are rather pleased. 13 00:00:35,640 --> 00:00:37,680 I don't think I can remember a year 14 00:00:37,680 --> 00:00:41,440 which has delivered so much in terms of discovery and exploration, 15 00:00:41,440 --> 00:00:42,960 and we've been lucky enough 16 00:00:42,960 --> 00:00:46,880 to have a ringside seat for many of this year's remarkable events. 17 00:00:46,880 --> 00:00:49,120 But the things that we report on are usually 18 00:00:49,120 --> 00:00:50,920 just the beginning of the story. 19 00:00:50,920 --> 00:00:53,400 The most exciting developments happen in the weeks 20 00:00:53,400 --> 00:00:56,560 and months that follow, as the serious science cuts in. 21 00:00:56,560 --> 00:00:59,600 And so tonight, we're bringing you bang up-to-date with many 22 00:00:59,600 --> 00:01:02,680 of the biggest stories of 2016. 23 00:01:02,680 --> 00:01:05,080 Welcome to The Sky At Night. 24 00:01:35,440 --> 00:01:38,920 There were four huge stories in 2016 and they've all seen 25 00:01:38,920 --> 00:01:42,480 significant new developments since we encountered them. 26 00:01:42,480 --> 00:01:45,720 Tonight we'll be looking back at these stories and revealing 27 00:01:45,720 --> 00:01:49,680 what's happened since we first reported on them. 28 00:01:49,680 --> 00:01:52,920 We'll be finding out more about Planet Nine, the mysterious planet 29 00:01:52,920 --> 00:01:57,080 that may orbit in the very outer reaches of the solar system. 30 00:01:59,000 --> 00:02:01,560 We'll be investigating what the recent discovery 31 00:02:01,560 --> 00:02:05,240 of gravitational waves can tell us about the rest of the universe. 32 00:02:06,640 --> 00:02:09,840 And we'll be asking whether we're any closer to understanding 33 00:02:09,840 --> 00:02:14,000 Proxima B, the newly-discovered and potentially earthlike planet 34 00:02:14,000 --> 00:02:16,600 orbiting our nearest neighbouring star. 35 00:02:18,520 --> 00:02:21,280 And if Father Christmas brings you a new telescope, 36 00:02:21,280 --> 00:02:24,320 then we have good news - Peter's here with a quick guide 37 00:02:24,320 --> 00:02:26,760 to show you how to get the best from it. 38 00:02:28,000 --> 00:02:29,480 But first we return 39 00:02:29,480 --> 00:02:32,040 to the biggest, most exciting mission of the year, 40 00:02:32,040 --> 00:02:35,240 one that would go where no spacecraft has gone before. 41 00:02:44,720 --> 00:02:48,680 Back in July, I travelled to NASA's Jet Propulsion Laboratory to witness 42 00:02:48,680 --> 00:02:53,360 the arrival of the Juno probe as it entered orbit around Jupiter. 43 00:02:53,360 --> 00:02:56,960 It was to be the first craft to slip through Jupiter's vast 44 00:02:56,960 --> 00:02:59,120 and intense radiation belts, 45 00:02:59,120 --> 00:03:04,840 flying just 5,000km above the gas giant's cloud tops. 46 00:03:04,840 --> 00:03:08,560 No-one knew if it would survive its entry into Jovian orbit. 47 00:03:11,400 --> 00:03:13,000 CHEERING AND APPLAUSE 48 00:03:13,000 --> 00:03:18,560 There it is! Juno right on time, into orbit, exactly as planned. 49 00:03:18,560 --> 00:03:22,480 After five years in space, Juno had made it into orbit 50 00:03:22,480 --> 00:03:27,400 within 1.2 seconds of the schedule, and the team was delighted. 51 00:03:27,400 --> 00:03:30,560 Ooh! Congratulations. Yay! 52 00:03:30,560 --> 00:03:32,680 So it went well, then? It went great! 53 00:03:32,680 --> 00:03:34,240 Just, I mean, what were they, 54 00:03:34,240 --> 00:03:37,960 like one second off, or something ridiculous? Perfect. 55 00:03:37,960 --> 00:03:40,880 It's perfect, so now we've got... The work is going to start. 56 00:03:40,880 --> 00:03:43,640 We get the data, we've got to do the work. 57 00:03:43,640 --> 00:03:45,720 In the five months since then, 58 00:03:45,720 --> 00:03:49,240 that work has started to deliver amazing results. 59 00:03:49,240 --> 00:03:52,760 Maggie met up with planetary scientist Leigh Fletcher 60 00:03:52,760 --> 00:03:56,160 to find out how the data that Juno has already returned 61 00:03:56,160 --> 00:03:59,960 are transforming our understanding of the giant planet. 62 00:03:59,960 --> 00:04:02,040 Leigh, thanks so much for coming in. 63 00:04:02,040 --> 00:04:04,760 Now, Juno's gone into orbit about Jupiter, 64 00:04:04,760 --> 00:04:06,680 but it's had a few challenges. 65 00:04:06,680 --> 00:04:10,720 Yes, when we first got into Jovian orbit back in July of 2016 66 00:04:10,720 --> 00:04:13,040 we went into a 53-day orbit. The idea was 67 00:04:13,040 --> 00:04:16,000 we were looping high over the North Pole, then coming in very, 68 00:04:16,000 --> 00:04:19,080 very close to the planet and going back out over the South Pole. 69 00:04:19,080 --> 00:04:23,040 Now, the plan all along had been to fire the engines in October 70 00:04:23,040 --> 00:04:26,000 of this year to move us from that 53-day orbit 71 00:04:26,000 --> 00:04:27,960 into a two-week orbit. 72 00:04:27,960 --> 00:04:31,000 Now, just before they were due to do that firing of the engine, 73 00:04:31,000 --> 00:04:33,520 they discovered that there was an issue with one of the valves, 74 00:04:33,520 --> 00:04:35,520 these are part of the propulsion system, 75 00:04:35,520 --> 00:04:38,400 they simply weren't opening and closing quite as quickly 76 00:04:38,400 --> 00:04:41,040 as they intended, so rather than take any risks, 77 00:04:41,040 --> 00:04:44,120 the programme managers decided that they were going to postpone 78 00:04:44,120 --> 00:04:48,200 that burn, and at the moment, we're staying in that 53-day orbit. 79 00:04:48,200 --> 00:04:50,920 Now to me, if you're in a 53-day orbit rather than 80 00:04:50,920 --> 00:04:53,520 a two-week orbit, that seems like less data. 81 00:04:53,520 --> 00:04:55,520 It's actually not a massive amount of difference. 82 00:04:55,520 --> 00:04:57,160 We'll get exactly the same science 83 00:04:57,160 --> 00:04:59,880 and we'll be covering exactly the same regions of the planet. 84 00:04:59,880 --> 00:05:01,280 It will just take longer, 85 00:05:01,280 --> 00:05:03,760 so we're having to learn to be slightly more patient. 86 00:05:03,760 --> 00:05:05,680 So, what did you see from that first encounter? 87 00:05:05,680 --> 00:05:07,960 Well, one of the wonderful things about Juno's orbit 88 00:05:07,960 --> 00:05:10,280 is it's giving us a vantage point we have never, 89 00:05:10,280 --> 00:05:13,520 ever had before, the ability to look at the poles of Jupiter. 90 00:05:13,520 --> 00:05:15,960 What I'm going to show you now is one of those first-ever 91 00:05:15,960 --> 00:05:18,640 images of the South Pole of Jupiter. 92 00:05:18,640 --> 00:05:21,160 So you're seeing light being reflected from the day side 93 00:05:21,160 --> 00:05:23,240 just here, and the night side down here, 94 00:05:23,240 --> 00:05:26,120 and as we zoom into this image, you can see the incredible 95 00:05:26,120 --> 00:05:29,440 structures that we're seeing here at the South Pole. 96 00:05:29,440 --> 00:05:33,040 These are pinwheel storms that are presumably moving 97 00:05:33,040 --> 00:05:35,880 and migrating all over the South Pole itself, so this is the 98 00:05:35,880 --> 00:05:38,920 South Pole of Jupiter, but of course we saw the North Pole as well. 99 00:05:38,920 --> 00:05:41,760 Here it is, again in this incredible detail. 100 00:05:41,760 --> 00:05:45,560 If we just zoom in again, you see all of these pinwheel storms 101 00:05:45,560 --> 00:05:48,800 and cyclones that are taking place, no belt zone structure, 102 00:05:48,800 --> 00:05:51,840 but the thing I'm most excited about is what's going on up here. 103 00:05:51,840 --> 00:05:55,280 What you have is a cloud that's actually rising up from the night 104 00:05:55,280 --> 00:05:59,040 side of Jupiter and it's getting so high in the planet's atmosphere 105 00:05:59,040 --> 00:06:03,280 that it's catching the dying rays of the sun as the sun is going down. 106 00:06:05,400 --> 00:06:08,760 As well as the camera, that operates in visible light, 107 00:06:08,760 --> 00:06:11,160 Juno is equipped with a whole suite of instruments 108 00:06:11,160 --> 00:06:13,040 to probe the planet in other ways... 109 00:06:14,480 --> 00:06:16,400 ..including its infrared imager 110 00:06:16,400 --> 00:06:18,800 that can penetrate Jupiter's cloud tops 111 00:06:18,800 --> 00:06:21,120 and reveal the vast scale of its aurorae. 112 00:06:22,400 --> 00:06:25,200 When we first saw this image, it really knocked our socks off. 113 00:06:25,200 --> 00:06:26,640 I'm not surprised. 114 00:06:26,640 --> 00:06:29,880 What you're looking at is the aurora at the South Pole of Jupiter, 115 00:06:29,880 --> 00:06:33,520 glowing because hydrogen ions are emitting their light 116 00:06:33,520 --> 00:06:36,200 as they're being bombarded by these electrons. 117 00:06:36,200 --> 00:06:39,760 It looks like a wall of fire, many times the size of the Earth. 118 00:06:39,760 --> 00:06:42,920 All of this incredible structure will be changing, 119 00:06:42,920 --> 00:06:46,280 ebbing and flowing over the course of just a few minutes. 120 00:06:46,280 --> 00:06:47,560 Amazing stuff. 121 00:06:47,560 --> 00:06:51,200 Now what I can show you next are the very first observations from 122 00:06:51,200 --> 00:06:54,320 the microwave instrument on board Juno that's allowing us 123 00:06:54,320 --> 00:06:56,480 to see down below the clouds. 124 00:06:56,480 --> 00:06:59,560 Now, this image on the right-hand side is what you're familiar with, 125 00:06:59,560 --> 00:07:01,520 it's the banded structure of Jupiter. 126 00:07:01,520 --> 00:07:03,880 We've got the red spot there, all of this looks very familiar. 127 00:07:03,880 --> 00:07:06,000 Absolutely, so this is light being reflected 128 00:07:06,000 --> 00:07:07,400 from the topmost cloud deck. 129 00:07:07,400 --> 00:07:10,800 These slices that you see on the left are probing deeper 130 00:07:10,800 --> 00:07:13,640 and deeper and deeper down into the interior depths. 131 00:07:13,640 --> 00:07:15,160 If you look at these, 132 00:07:15,160 --> 00:07:18,480 it's obvious that we are actually seeing banded structures still 133 00:07:18,480 --> 00:07:23,320 down in the interior of Jupiter, down 300km below these cloud decks. 134 00:07:23,320 --> 00:07:26,480 So what this means is that the surface that we're seeing 135 00:07:26,480 --> 00:07:30,360 is just the tip of the iceberg and that below that tip we're seeing 136 00:07:30,360 --> 00:07:34,120 an enormous circulation or atmospheric pattern that will 137 00:07:34,120 --> 00:07:37,320 keep atmospheric scientists going for years, trying to interpret 138 00:07:37,320 --> 00:07:38,960 what is actually taking place. 139 00:07:38,960 --> 00:07:42,000 Please come back again and tell us more about this amazing planet. 140 00:07:42,000 --> 00:07:44,440 Will do, thank you. Thank you very much. 141 00:07:44,440 --> 00:07:48,840 And that brings us to our second highlight of the year. 142 00:07:55,640 --> 00:07:59,880 At the end of August, just days before Juno's first close pass 143 00:07:59,880 --> 00:08:04,600 around Jupiter, news came of another tremendously exciting announcement. 144 00:08:08,320 --> 00:08:10,840 Now scientists are hailing a major discovery, 145 00:08:10,840 --> 00:08:13,720 a new planet which they've called Proxima B. 146 00:08:13,720 --> 00:08:17,120 At just four light years away, it's relatively close to us. 147 00:08:17,120 --> 00:08:19,160 It's roughly the same size as Earth, 148 00:08:19,160 --> 00:08:21,840 and because it's just the right distance away from its star, 149 00:08:21,840 --> 00:08:25,840 it could be the right temperature to have liquid water and possibly life. 150 00:08:27,840 --> 00:08:30,840 The planet was found orbiting Proxima Centauri, 151 00:08:30,840 --> 00:08:33,200 our closest neighbouring star. 152 00:08:33,200 --> 00:08:36,280 At just over four light years away, it's just close enough 153 00:08:36,280 --> 00:08:40,120 to imagine that we might one day be able to send a spacecraft there. 154 00:08:44,200 --> 00:08:47,320 Having a planet around Proxima is exciting and pretty much 155 00:08:47,320 --> 00:08:51,240 everyone who studies exoplanets has scrambled to have their say 156 00:08:51,240 --> 00:08:53,240 about what it must really be like. 157 00:08:54,920 --> 00:08:58,480 In some ways, the planet is very different from the Earth. 158 00:08:58,480 --> 00:09:03,080 It orbits just 7.5 million kilometres from its star - 159 00:09:03,080 --> 00:09:06,880 that's roughly 20 times closer than the Earth is to the sun. 160 00:09:08,120 --> 00:09:11,400 But because Proxima Centauri is so much cooler and dimmer 161 00:09:11,400 --> 00:09:15,920 than our sun, the planet could be a similar temperature to the Earth. 162 00:09:15,920 --> 00:09:19,880 But being so close to its star could also create other problems. 163 00:09:21,240 --> 00:09:25,160 For example, it was thought that Proxima was a violent star, 164 00:09:25,160 --> 00:09:27,840 sending stellar flares towards the planet, 165 00:09:27,840 --> 00:09:30,240 and making it an inhospitable place. 166 00:09:31,880 --> 00:09:35,640 But new research seems to show that it's no more violent than our sun. 167 00:09:37,320 --> 00:09:39,240 But there remain many unknowns. 168 00:09:39,240 --> 00:09:42,280 We've no real idea what the planet is like. 169 00:09:42,280 --> 00:09:45,520 We can't observe it directly and so everything we know 170 00:09:45,520 --> 00:09:48,800 we've had to infer by watching the gravitational effect 171 00:09:48,800 --> 00:09:50,360 that it has on its star. 172 00:09:51,520 --> 00:09:54,440 And so a French team have tried to work out the planet's 173 00:09:54,440 --> 00:09:57,880 characteristics by using comparisons with the planets 174 00:09:57,880 --> 00:10:00,120 in our own solar system. 175 00:10:01,880 --> 00:10:05,360 If it has a large metallic core and a rocky mantle, 176 00:10:05,360 --> 00:10:06,800 like Mercury does, 177 00:10:06,800 --> 00:10:09,480 then it's probably a little bit smaller than the Earth, 178 00:10:09,480 --> 00:10:12,560 but there are other, more exotic possibilities. 179 00:10:12,560 --> 00:10:17,440 It could be much bigger than the Earth, 1.4 times the size, 180 00:10:17,440 --> 00:10:20,920 in which case it would have to have a rocky core, surrounded by 181 00:10:20,920 --> 00:10:25,120 a mantle of ice, and excitingly, the model suggests that 182 00:10:25,120 --> 00:10:29,080 the entire planet would then be covered in a vast ocean, 200km deep. 183 00:10:31,920 --> 00:10:34,080 All this speculation is great fun, 184 00:10:34,080 --> 00:10:37,720 but what we really need are more observations. 185 00:10:37,720 --> 00:10:41,600 But those observations will be extremely challenging. 186 00:10:41,600 --> 00:10:45,640 The planet is too small and too faint to be directly imaged 187 00:10:45,640 --> 00:10:47,600 with current telescopes. 188 00:10:47,600 --> 00:10:50,680 And so we must wait for the next generation of instruments 189 00:10:50,680 --> 00:10:53,760 before we can understand its true nature. 190 00:10:53,760 --> 00:10:57,040 The story of Proxima B has a long way to run. 191 00:11:01,800 --> 00:11:05,000 Earlier this year we asked for your help to identify 192 00:11:05,000 --> 00:11:08,240 a new class of comet hidden in the asteroid belt. 193 00:11:08,240 --> 00:11:11,800 These main belt comets are similar to ordinary asteroids, 194 00:11:11,800 --> 00:11:14,240 apart from they occasionally sprout tails. 195 00:11:16,240 --> 00:11:19,360 Very little is known about these strange objects, 196 00:11:19,360 --> 00:11:22,760 but their tails are almost certainly produced by pockets of ice, 197 00:11:22,760 --> 00:11:25,160 vaporising as they are heated by the sun. 198 00:11:26,880 --> 00:11:29,920 That means that these main belt comets could represent 199 00:11:29,920 --> 00:11:33,920 a huge and previously unknown source of water in the inner solar system. 200 00:11:35,360 --> 00:11:37,760 But only a handful have been found, 201 00:11:37,760 --> 00:11:41,200 so we sent out a call to get you searching for them. 202 00:11:41,200 --> 00:11:44,600 We had a fantastic response and Sky At Night viewers have 203 00:11:44,600 --> 00:11:48,960 contributed to identifying over 340,000 images to date. 204 00:11:51,000 --> 00:11:54,120 And from them, you identified these two, which appear to be 205 00:11:54,120 --> 00:11:59,240 producing tails and which could be newly-discovered comets. 206 00:11:59,240 --> 00:12:01,760 The next step is to observe these objects 207 00:12:01,760 --> 00:12:05,240 through the 8.2-metre Subaru telescope in Hawaii. 208 00:12:05,240 --> 00:12:08,160 This will hopefully occur early next year and it will help 209 00:12:08,160 --> 00:12:11,960 the team to identify whether these really are main belt comets, 210 00:12:11,960 --> 00:12:14,680 and we'll bring you the results as soon as we have them. 211 00:12:25,120 --> 00:12:28,080 The Comet Hunters project shows the power and the potential 212 00:12:28,080 --> 00:12:30,600 of everyone to make new discoveries. 213 00:12:34,120 --> 00:12:37,880 If you're inspired to become a stargazer yourself, 214 00:12:37,880 --> 00:12:41,000 or if you're getting a telescope for Christmas, Pete is here 215 00:12:41,000 --> 00:12:43,440 with some tips on how to get the best results. 216 00:12:47,280 --> 00:12:48,680 Now, it's probably fair to say 217 00:12:48,680 --> 00:12:50,800 that astronomy isn't the cheapest of hobbies, 218 00:12:50,800 --> 00:12:53,600 but for a few hundred pounds you can get some pretty decent kit 219 00:12:53,600 --> 00:12:56,000 and there are plenty of manufacturers out there that 220 00:12:56,000 --> 00:12:57,600 make packages such as this. 221 00:12:57,600 --> 00:13:01,040 Now, here I've got a very sturdy tripod at the bottom 222 00:13:01,040 --> 00:13:02,600 to hold everything very steady. 223 00:13:02,600 --> 00:13:05,520 On top of that, I've got an equatorial mount head, 224 00:13:05,520 --> 00:13:07,800 and this one has a motor attached to it. 225 00:13:07,800 --> 00:13:11,480 Now this has the job of counteracting the Earth's rotation, 226 00:13:11,480 --> 00:13:15,040 so it keeps everything that I'm looking at through the eyepiece 227 00:13:15,040 --> 00:13:16,880 in exactly the same position. 228 00:13:16,880 --> 00:13:19,560 On top of that, I've got my telescope tube, 229 00:13:19,560 --> 00:13:23,200 and in this case, this is a 70mm refracting telescope. 230 00:13:26,080 --> 00:13:29,480 This is an ideal size to view the moon and deep sky objects, 231 00:13:29,480 --> 00:13:32,720 such as open clusters and galaxies. 232 00:13:32,720 --> 00:13:35,120 To align the telescope properly, 233 00:13:35,120 --> 00:13:37,720 it needs to be balanced on the mount. 234 00:13:37,720 --> 00:13:41,200 And the mount needs to be pointed as accurately as possible 235 00:13:41,200 --> 00:13:44,520 at the celestial pole, which is close to the North Star. 236 00:13:45,880 --> 00:13:49,320 Once you've got your telescope set up, you need to leave it 237 00:13:49,320 --> 00:13:52,920 for about an hour to cool down to the outside temperature. 238 00:13:52,920 --> 00:13:56,360 That will also allow your eyes to adapt to the darkness. 239 00:13:59,240 --> 00:14:01,640 And then you are ready to start observing. 240 00:14:01,640 --> 00:14:04,560 And what I'm going to line up on tonight is the Andromeda Galaxy, 241 00:14:04,560 --> 00:14:06,080 Messier 31. 242 00:14:06,080 --> 00:14:08,960 That's our nearest, largest neighbouring galaxy. 243 00:14:11,400 --> 00:14:14,480 The Andromeda Galaxy is located almost overhead 244 00:14:14,480 --> 00:14:15,960 during early evening 245 00:14:15,960 --> 00:14:17,320 to the north-east of 246 00:14:17,320 --> 00:14:19,240 the Great Square of Pegasus. 247 00:14:19,240 --> 00:14:23,000 Use the right-hand side of the W-shape constellation of 248 00:14:23,000 --> 00:14:25,080 Cassiopeia as a pointer to it. 249 00:14:25,080 --> 00:14:27,320 Point your scope at the galaxy, 250 00:14:27,320 --> 00:14:30,520 lining its elliptical haze up with the finder's crosshairs. 251 00:14:35,040 --> 00:14:38,080 If you want to take pictures of what you're observing, 252 00:14:38,080 --> 00:14:41,440 you can add an adapter ring that will connect most DSLR cameras 253 00:14:41,440 --> 00:14:43,200 to the telescope. 254 00:14:43,200 --> 00:14:46,360 But bear in mind that you'll have to rebalance the scope 255 00:14:46,360 --> 00:14:48,680 to take into account the weight of the camera. 256 00:14:49,840 --> 00:14:54,000 So, trying the ISO setting of between 400 and 1,600, 257 00:14:54,000 --> 00:14:57,520 the higher you go, the noisier the end result will be. 258 00:14:57,520 --> 00:15:02,720 Also an inexpensive shutter release cable like this is a great idea, 259 00:15:02,720 --> 00:15:06,040 because it allows you to take your pictures without 260 00:15:06,040 --> 00:15:08,680 touching the camera and wobbling the telescope. 261 00:15:08,680 --> 00:15:12,320 Now, for a tracking mount like this, exposures between, 262 00:15:12,320 --> 00:15:16,120 say, 30 and 120 seconds are possible. 263 00:15:16,120 --> 00:15:18,800 The key to success is to experiment. 264 00:15:19,960 --> 00:15:23,920 There it is, the Andromeda Galaxy, and beautiful it looks too. 265 00:15:23,920 --> 00:15:25,960 Look at that, there's so much detail in there. 266 00:15:25,960 --> 00:15:29,000 I've got the core, I've got the spiral arms which are really 267 00:15:29,000 --> 00:15:31,280 faint, sort of, going round the core, 268 00:15:31,280 --> 00:15:35,360 and I can see the dark dust lanes running through the galaxy as well. 269 00:15:35,360 --> 00:15:41,280 And I've got the satellite galaxies, M32 and M110, also in that shot. 270 00:15:41,280 --> 00:15:45,280 Loads of detail. And with a fairly basic set-up. It's amazing. 271 00:15:56,720 --> 00:16:01,080 Our third highlight of the year was announced way back in January. 272 00:16:01,080 --> 00:16:05,320 And it took both the scientific community and the public by surprise. 273 00:16:11,240 --> 00:16:14,240 A team of researchers from Caltech claimed that they had 274 00:16:14,240 --> 00:16:15,880 evidence for a ninth planet. 275 00:16:17,320 --> 00:16:20,280 Hidden in the outer reaches of our solar system, 276 00:16:20,280 --> 00:16:22,400 far beyond the icy realm of the Kuiper Belt. 277 00:16:24,040 --> 00:16:27,880 I set out to demonstrate just how extreme this planet's orbit was. 278 00:16:29,720 --> 00:16:34,440 On this scale, every centimetre is about 35 million kilometres. 279 00:16:36,120 --> 00:16:38,800 The Earth is 150 million kilometres from the sun. 280 00:16:40,280 --> 00:16:42,720 Pluto is 40 times further away 281 00:16:42,720 --> 00:16:46,520 and the outer edge of the Kuiper Belt is still further. 282 00:16:47,880 --> 00:16:50,040 But Planet Nine is far beyond that. 283 00:16:50,040 --> 00:16:52,920 At the point of closest approach in its orbit, 284 00:16:52,920 --> 00:16:56,320 it sits 200 times further from the sun than the Earth. 285 00:16:56,320 --> 00:16:59,920 That's a whopping 30 billion kilometres away from the sun. 286 00:17:01,760 --> 00:17:03,680 But unlike the other planets, 287 00:17:03,680 --> 00:17:06,440 the proposed orbit of Planet Nine is not circular. 288 00:17:08,520 --> 00:17:12,040 Its highly eccentric path takes it much, much deeper into space. 289 00:17:15,040 --> 00:17:18,920 At its furthest possible point, its aphelion, 290 00:17:18,920 --> 00:17:22,720 it could be as much as 1,200 times further from the sun than the Earth. 291 00:17:25,960 --> 00:17:28,240 On this scale it's 54 metres away. 292 00:17:29,640 --> 00:17:33,920 In reality it would be 180 billion kilometres from the sun. 293 00:17:35,400 --> 00:17:38,200 This discovery was enormous news, 294 00:17:38,200 --> 00:17:41,360 but there was one crucial stumbling block. 295 00:17:41,360 --> 00:17:44,760 No-one had actually seen Planet Nine. 296 00:17:44,760 --> 00:17:48,360 Its existence had only been predicted by computer models 297 00:17:48,360 --> 00:17:53,920 that had been built by Caltech astronomers Mike Brown and Constantine Batygin. 298 00:17:53,920 --> 00:17:57,880 They'd been trying to understand the unusual elliptical orbits of 299 00:17:57,880 --> 00:18:02,040 six distant objects out in the Kuiper Belt, seen here in pink. 300 00:18:03,280 --> 00:18:05,960 They found that the only way they could replicate these orbits 301 00:18:05,960 --> 00:18:09,960 was if there was a ninth planet orbiting far beyond Neptune. 302 00:18:12,720 --> 00:18:16,200 When I met Mike shortly after the announcement in January, 303 00:18:16,200 --> 00:18:20,040 he explained to me that the next challenge would be to find the planet. 304 00:18:21,720 --> 00:18:25,480 Clear sky, sort of. Where is it? Where's this planet? 305 00:18:25,480 --> 00:18:28,520 Well, we know its path across the sky. 306 00:18:28,520 --> 00:18:33,200 We know its orbit, so we know the path and the path across the sky goes from somewhere over here, 307 00:18:33,200 --> 00:18:38,480 up across here right through the middle of Orion and Taurus and then down south across this way, 308 00:18:38,480 --> 00:18:40,760 and then of course all the way back around. 309 00:18:40,760 --> 00:18:44,960 We actually also know that around Orion and Taurus is where it's 310 00:18:44,960 --> 00:18:47,040 the most distant from the sun. 311 00:18:47,040 --> 00:18:48,560 And we think that's where it is. 312 00:18:48,560 --> 00:18:53,040 We think that the places that are closer to the sun, it would be too bright, we would have seen it. 313 00:18:53,040 --> 00:18:55,600 I mean, we're not talking amateur telescopes here to find this. 314 00:18:55,600 --> 00:18:59,040 No, in the end it's going to take us some time on the biggest 315 00:18:59,040 --> 00:19:03,080 telescopes in the world, but with the biggest telescopes in the world, 316 00:19:03,080 --> 00:19:06,080 it is well within range and we'll be able to find it. 317 00:19:06,080 --> 00:19:08,760 It's up there somewhere, probably. Right there. 318 00:19:11,800 --> 00:19:15,600 Many astronomers are yet to be convinced, and so I recently 319 00:19:15,600 --> 00:19:19,360 caught up with Mike again to see how the search was going. 320 00:19:19,360 --> 00:19:22,600 Hello? Hey, Mike, it's Chris. How are you? 321 00:19:22,600 --> 00:19:25,320 Good, Chris, how are you? Yeah, nice to see you. 322 00:19:25,320 --> 00:19:27,720 So, look, I'm not going to waste any time. 323 00:19:27,720 --> 00:19:29,520 Have you found Planet Nine yet? 324 00:19:29,520 --> 00:19:32,480 No. Excellent, thank you! THEY LAUGH 325 00:19:32,480 --> 00:19:34,840 What progress do you have to report? 326 00:19:34,840 --> 00:19:38,440 My favourite one that we realised just this last summer is 327 00:19:38,440 --> 00:19:41,680 something that has been known since 1850 and has had 328 00:19:41,680 --> 00:19:45,960 no explanation, which is if you look at the planets of our solar system, 329 00:19:45,960 --> 00:19:48,080 all eight planets, they're in a disc. 330 00:19:48,080 --> 00:19:51,360 And that disc, the inclinations, 331 00:19:51,360 --> 00:19:53,520 the amount that they're tilted relative to each other, 332 00:19:53,520 --> 00:19:55,600 is less than one degree on average, 333 00:19:55,600 --> 00:19:59,160 so all eight planets are within this one little one-degree disc. 334 00:19:59,160 --> 00:20:03,600 The sun is tilted from that disc by about six degrees. 335 00:20:03,600 --> 00:20:05,520 It's really a strange thing. 336 00:20:05,520 --> 00:20:10,920 No-one has had a very good explanation for 160 years. 337 00:20:10,920 --> 00:20:16,840 And in fact it's been so unexplainable that most people don't even realise that it's true. 338 00:20:16,840 --> 00:20:19,880 So, we quickly sat down and did this calculation to figure it out 339 00:20:19,880 --> 00:20:23,840 and realised that our prediction of Planet Nine, and of where Planet 340 00:20:23,840 --> 00:20:28,440 Nine is, predicts about a six-degree tilt just like the tilt that we see 341 00:20:28,440 --> 00:20:33,000 and the exact direction that the sun is actually tilted. 342 00:20:33,000 --> 00:20:36,320 It was one of those remarkable moments where you do this 343 00:20:36,320 --> 00:20:38,720 calculation not knowing what the answer's going to be, 344 00:20:38,720 --> 00:20:42,160 and it comes out exactly what you were hoping it was going to be. 345 00:20:42,160 --> 00:20:45,880 So, lots of people are looking. Have you had sceptical reaction as well? 346 00:20:45,880 --> 00:20:48,040 Clearly not everyone's as sure as you are. 347 00:20:48,040 --> 00:20:50,160 What have the negative reactions been? 348 00:20:50,160 --> 00:20:53,160 Are people still questioning whether this is just chance, these alignments? 349 00:20:53,160 --> 00:20:57,880 Yeah, so, scientists as a rule are a sceptical tribe, 350 00:20:57,880 --> 00:21:01,160 and if you're going to be sceptical of anything, 351 00:21:01,160 --> 00:21:05,400 you should be sceptical of somebody claiming there's a planet out in the outer solar system, 352 00:21:05,400 --> 00:21:08,640 because people have been claiming this for 353 00:21:08,640 --> 00:21:13,720 approximately the last 165 years, and every time it's been a mistake. 354 00:21:13,720 --> 00:21:16,640 So, there are people trying very hard to show that it's not true. 355 00:21:16,640 --> 00:21:22,120 So far I haven't seen anything that has been convincingly showing 356 00:21:22,120 --> 00:21:24,280 that it's not really out there. 357 00:21:24,280 --> 00:21:27,200 Well, just before we let you go to get back to trying to find this 358 00:21:27,200 --> 00:21:33,200 thing for us, I'm going to make you bet, I think - next year, 2017? 359 00:21:33,200 --> 00:21:38,520 At the beginning of this year, I was cautious and I said five years. 360 00:21:38,520 --> 00:21:44,080 And now, I tell you, we have narrowed down the search area 361 00:21:44,080 --> 00:21:46,880 to such a small area with these calculations. 362 00:21:46,880 --> 00:21:49,760 I'm going to guess that next year... 363 00:21:49,760 --> 00:21:51,320 Next year's the year. 364 00:21:51,320 --> 00:21:54,880 I'm... I feel optimistic. 365 00:21:54,880 --> 00:21:57,160 OK, well, we'll talk to you then. Good luck. 366 00:21:57,160 --> 00:21:59,320 All right, thank you very much. Thanks, Mike. 367 00:22:01,920 --> 00:22:04,000 Mike certainly sounds convinced, 368 00:22:04,000 --> 00:22:06,120 even more than he did at the start of the year, 369 00:22:06,120 --> 00:22:08,760 and the evidence does seem to be piling up, 370 00:22:08,760 --> 00:22:13,360 so let's hope he's right and 2017 is the year that we find Planet Nine. 371 00:22:19,720 --> 00:22:23,760 Our fourth and final story comes from much, much deeper in space. 372 00:22:30,720 --> 00:22:36,240 Back in January, Planet Nine was described as potentially the discovery of the century. 373 00:22:36,240 --> 00:22:39,200 But then, just three weeks later, scientists at the Advanced 374 00:22:39,200 --> 00:22:42,840 LIGO instrument in the States made an even bigger announcement. 375 00:22:44,640 --> 00:22:47,200 BBC NEWS HEADLINES: Unravelling the secrets of the universe - 376 00:22:47,200 --> 00:22:50,600 the most important scientific discovery for a generation. 377 00:22:50,600 --> 00:22:53,720 Scientists in the United States have announced they have 378 00:22:53,720 --> 00:22:55,680 discovered gravitational waves. 379 00:22:55,680 --> 00:22:57,520 Einstein was right after all. 380 00:22:57,520 --> 00:23:00,400 Gravitational waves ripple through space and time. 381 00:23:02,080 --> 00:23:04,480 Gravitational waves were a key feature of Einstein's theory 382 00:23:04,480 --> 00:23:06,200 of general relativity. 383 00:23:06,200 --> 00:23:08,840 And the fact that they were discovered exactly a century after 384 00:23:08,840 --> 00:23:12,040 he predicted them strengthens his theory. 385 00:23:12,040 --> 00:23:14,200 But gravitational waves gives us so much more, 386 00:23:14,200 --> 00:23:17,840 cos they allow us to see some of the most exotic bodies in the universe, 387 00:23:17,840 --> 00:23:20,400 because what LIGO had detected was the collision 388 00:23:20,400 --> 00:23:22,000 between two black holes. 389 00:23:28,720 --> 00:23:31,920 Black holes are difficult to study by conventional means, 390 00:23:31,920 --> 00:23:33,840 because they do not emit any light. 391 00:23:36,720 --> 00:23:39,200 But the LIGO measurements suddenly gave us 392 00:23:39,200 --> 00:23:42,680 a way to observe exactly what happens when black holes collide. 393 00:23:45,680 --> 00:23:49,080 1.3 billion light years away the two black holes, 394 00:23:49,080 --> 00:23:52,160 36 and 29 times the mass of the sun, 395 00:23:52,160 --> 00:23:56,840 have been orbiting each other in a binary system, before colliding 396 00:23:56,840 --> 00:24:00,480 with such force that they sent tremors rippling through space-time. 397 00:24:08,560 --> 00:24:10,720 But by the time they reached Earth, 398 00:24:10,720 --> 00:24:14,080 the waves had dissipated so much they caused a disturbance in 399 00:24:14,080 --> 00:24:18,320 LIGO's detectors that was only 1/1000th the width of a proton. 400 00:24:19,760 --> 00:24:22,960 A lot has happened since we brought you that first detection. 401 00:24:22,960 --> 00:24:24,680 In fact, just three months later, 402 00:24:24,680 --> 00:24:27,560 another collision between black holes was detected and then 403 00:24:27,560 --> 00:24:30,440 a third, but the signal for that one was 404 00:24:30,440 --> 00:24:32,360 a bit too weak to get full confirmation. 405 00:24:32,360 --> 00:24:35,360 But this collection of collisions gives us an indication that 406 00:24:35,360 --> 00:24:38,960 these events which we thought were rare may be relatively common. 407 00:24:43,240 --> 00:24:47,840 And these new discoveries are also causing us to reassess our ideas 408 00:24:47,840 --> 00:24:51,080 about the nature and formation of black holes. 409 00:24:51,080 --> 00:24:55,200 The data had revealed that some black holes spin at enormous 410 00:24:55,200 --> 00:24:59,680 speeds, 10% of the speed of light, much faster than we expected. 411 00:25:03,200 --> 00:25:05,760 And then there's a problem that the black holes detected in 412 00:25:05,760 --> 00:25:09,520 the first collision are far too massive to exist in a binary system. 413 00:25:15,240 --> 00:25:18,480 Black holes form from the collapse of massive stars at the end 414 00:25:18,480 --> 00:25:19,600 of their lifetimes. 415 00:25:21,320 --> 00:25:24,360 It had always been assumed that black hole pairs formed 416 00:25:24,360 --> 00:25:25,840 from binary star systems. 417 00:25:27,200 --> 00:25:30,760 But the black holes in the LIGO observations are so vast, they 418 00:25:30,760 --> 00:25:34,840 must have formed from stars that were too big to survive as binaries. 419 00:25:36,120 --> 00:25:39,120 They would have fallen into each other and merged long before 420 00:25:39,120 --> 00:25:41,120 they could have formed black holes. 421 00:25:42,280 --> 00:25:46,000 So, we need a new model to understand how black holes collide. 422 00:25:47,560 --> 00:25:51,480 It may be that instead of forming in a binary star system 423 00:25:51,480 --> 00:25:54,240 that the two black holes formed independently, 424 00:25:54,240 --> 00:25:58,120 maybe in a dense star cluster, then gravitated towards each other, 425 00:25:58,120 --> 00:26:01,160 forming a binary pair which then collapsed. 426 00:26:06,200 --> 00:26:09,880 What's really exciting about this gravitational wave discovery 427 00:26:09,880 --> 00:26:13,440 is that it lets us see things that were previously hidden. 428 00:26:13,440 --> 00:26:17,400 Instead of relying on light in looking only at things that shine, 429 00:26:17,400 --> 00:26:21,520 we have a whole new way to observe the universe. 430 00:26:21,520 --> 00:26:25,680 LIGO has just begun its second run, and detections are expected 431 00:26:25,680 --> 00:26:29,760 to come thick and fast over the coming months and years. 432 00:26:29,760 --> 00:26:32,640 We don't know what these next observations will reveal, 433 00:26:32,640 --> 00:26:36,080 but we do know that when people look back at this first discovery 434 00:26:36,080 --> 00:26:40,080 in 2016, they'll see it as a great moment in the history of 435 00:26:40,080 --> 00:26:44,280 astronomy, as transformative as the invention of the radio telescope. 436 00:26:46,400 --> 00:26:50,680 That brings us to the end of the four major stories we covered this year. 437 00:26:52,120 --> 00:26:54,920 But there have been many other exciting events 438 00:26:54,920 --> 00:26:57,120 that slipped by without fanfare. 439 00:26:57,120 --> 00:26:58,840 Two. One... 440 00:26:58,840 --> 00:27:02,920 In September we saw the launch of Osiris Rex, an ambitious 441 00:27:02,920 --> 00:27:08,080 new mission to collect a sample of an asteroid and return it to Earth. 442 00:27:08,080 --> 00:27:10,120 Elsewhere in the solar system, 443 00:27:10,120 --> 00:27:13,040 it's been a good year for discovering water. 444 00:27:13,040 --> 00:27:17,040 An ice volcano twice the size of Everest was found 445 00:27:17,040 --> 00:27:19,280 on the dwarf planet Ceres. 446 00:27:19,280 --> 00:27:23,200 Plumes of water had been detected erupting from Jupiter's moon Europa. 447 00:27:24,360 --> 00:27:26,800 And there's fresh evidence for the existence of 448 00:27:26,800 --> 00:27:28,440 a subsurface ocean on Pluto. 449 00:27:30,360 --> 00:27:34,320 Further afield, astronomers have discovered that there are ten times 450 00:27:34,320 --> 00:27:38,520 more galaxies in the observable universe than first thought. 451 00:27:38,520 --> 00:27:39,960 Some two trillion of them. 452 00:27:41,240 --> 00:27:43,560 One of them, Dragonfly 44, 453 00:27:43,560 --> 00:27:47,560 has been found to be made of 99.9% dark matter. 454 00:27:48,680 --> 00:27:52,200 Making it the largest dark matter galaxy ever observed. 455 00:27:54,240 --> 00:27:56,240 2016 is coming to an end, 456 00:27:56,240 --> 00:27:58,320 but there's lots of exciting stuff for the New Year. 457 00:27:58,320 --> 00:28:01,520 Yes, we've got the launch of not one but two exoplanet missions, 458 00:28:01,520 --> 00:28:03,240 a total solar eclipse in the US, 459 00:28:03,240 --> 00:28:06,920 more from LIGO and I'm looking forward to Curiosity climbing 460 00:28:06,920 --> 00:28:09,880 the slopes of Mount Sharp, but what are you most excited about? 461 00:28:09,880 --> 00:28:12,760 Well, for me it is all about the end of Cassini. It's been an epic 462 00:28:12,760 --> 00:28:15,280 mission and now it's coming to an end, and it's going to be 463 00:28:15,280 --> 00:28:18,880 a grand finale as the spacecraft plunges into the depths of Saturn. 464 00:28:18,880 --> 00:28:22,600 What a way to go. Yeah, it's a shame it's got to end, but it will be spectacular. 465 00:28:22,600 --> 00:28:25,400 That's it from us from this year, but we'll be back in January, 466 00:28:25,400 --> 00:28:27,040 so you don't have long to wait. 467 00:28:27,040 --> 00:28:29,800 And in the meantime, don't forget to go to the website to check out 468 00:28:29,800 --> 00:28:32,320 this month's guide to the night sky. 469 00:28:32,320 --> 00:28:35,840 And, as usual, get outside and get looking up. 470 00:28:35,840 --> 00:28:37,080 Goodnight.