0:00:02 > 0:00:05- Thank you.- 2016 will be remembered for many different reasons.
0:00:05 > 0:00:07Brexit means Brexit...
0:00:07 > 0:00:10But whatever you thought of the events of this year,
0:00:10 > 0:00:12one thing is certain -
0:00:12 > 0:00:15it has been one of the most extraordinary years
0:00:15 > 0:00:17in space exploration.
0:00:17 > 0:00:20Scientists are hailing a major discovery...
0:00:20 > 0:00:22We have detected...
0:00:22 > 0:00:25gravitational waves. We did it.
0:00:25 > 0:00:27CHEERING AND APPLAUSE
0:00:27 > 0:00:30We have a spacecraft in orbit around Jupiter,
0:00:30 > 0:00:32and I think people are rather pleased.
0:00:35 > 0:00:37I don't think I can remember a year
0:00:37 > 0:00:41which has delivered so much in terms of discovery and exploration,
0:00:41 > 0:00:42and we've been lucky enough
0:00:42 > 0:00:46to have a ringside seat for many of this year's remarkable events.
0:00:46 > 0:00:48But the things that we report on are usually
0:00:48 > 0:00:50just the beginning of the story.
0:00:50 > 0:00:53The most exciting developments happen in the weeks
0:00:53 > 0:00:56and months that follow, as the serious science cuts in.
0:00:56 > 0:00:59And so tonight, we're bringing you bang up-to-date with many
0:00:59 > 0:01:02of the biggest stories of 2016.
0:01:02 > 0:01:04Welcome to The Sky At Night.
0:01:35 > 0:01:38There were four huge stories in 2016 and they've all seen
0:01:38 > 0:01:42significant new developments since we encountered them.
0:01:42 > 0:01:45Tonight we'll be looking back at these stories and revealing
0:01:45 > 0:01:49what's happened since we first reported on them.
0:01:49 > 0:01:52We'll be finding out more about Planet Nine, the mysterious planet
0:01:52 > 0:01:56that may orbit in the very outer reaches of the solar system.
0:01:58 > 0:02:01We'll be investigating what the recent discovery
0:02:01 > 0:02:05of gravitational waves can tell us about the rest of the universe.
0:02:06 > 0:02:09And we'll be asking whether we're any closer to understanding
0:02:09 > 0:02:13Proxima B, the newly-discovered and potentially earthlike planet
0:02:13 > 0:02:16orbiting our nearest neighbouring star.
0:02:18 > 0:02:20And if Father Christmas brings you a new telescope,
0:02:20 > 0:02:23then we have good news - Peter's here with a quick guide
0:02:23 > 0:02:26to show you how to get the best from it.
0:02:27 > 0:02:29But first we return
0:02:29 > 0:02:31to the biggest, most exciting mission of the year,
0:02:31 > 0:02:35one that would go where no spacecraft has gone before.
0:02:44 > 0:02:48Back in July, I travelled to NASA's Jet Propulsion Laboratory to witness
0:02:48 > 0:02:53the arrival of the Juno probe as it entered orbit around Jupiter.
0:02:53 > 0:02:56It was to be the first craft to slip through Jupiter's vast
0:02:56 > 0:02:58and intense radiation belts,
0:02:58 > 0:03:04flying just 5,000km above the gas giant's cloud tops.
0:03:04 > 0:03:08No-one knew if it would survive its entry into Jovian orbit.
0:03:11 > 0:03:12CHEERING AND APPLAUSE
0:03:12 > 0:03:18There it is! Juno right on time, into orbit, exactly as planned.
0:03:18 > 0:03:22After five years in space, Juno had made it into orbit
0:03:22 > 0:03:27within 1.2 seconds of the schedule, and the team was delighted.
0:03:27 > 0:03:30- Ooh!- Congratulations.- Yay!
0:03:30 > 0:03:32- So it went well, then? - It went great!
0:03:32 > 0:03:33Just, I mean, what were they,
0:03:33 > 0:03:37- like one second off, or something ridiculous?- Perfect.
0:03:37 > 0:03:40It's perfect, so now we've got... The work is going to start.
0:03:40 > 0:03:43We get the data, we've got to do the work.
0:03:43 > 0:03:45In the five months since then,
0:03:45 > 0:03:48that work has started to deliver amazing results.
0:03:48 > 0:03:52Maggie met up with planetary scientist Leigh Fletcher
0:03:52 > 0:03:55to find out how the data that Juno has already returned
0:03:55 > 0:03:59are transforming our understanding of the giant planet.
0:03:59 > 0:04:01Leigh, thanks so much for coming in.
0:04:01 > 0:04:04Now, Juno's gone into orbit about Jupiter,
0:04:04 > 0:04:06but it's had a few challenges.
0:04:06 > 0:04:10Yes, when we first got into Jovian orbit back in July of 2016
0:04:10 > 0:04:12we went into a 53-day orbit. The idea was
0:04:12 > 0:04:15we were looping high over the North Pole, then coming in very,
0:04:15 > 0:04:18very close to the planet and going back out over the South Pole.
0:04:18 > 0:04:22Now, the plan all along had been to fire the engines in October
0:04:22 > 0:04:25of this year to move us from that 53-day orbit
0:04:25 > 0:04:27into a two-week orbit.
0:04:27 > 0:04:30Now, just before they were due to do that firing of the engine,
0:04:30 > 0:04:33they discovered that there was an issue with one of the valves,
0:04:33 > 0:04:35these are part of the propulsion system,
0:04:35 > 0:04:38they simply weren't opening and closing quite as quickly
0:04:38 > 0:04:40as they intended, so rather than take any risks,
0:04:40 > 0:04:43the programme managers decided that they were going to postpone
0:04:43 > 0:04:47that burn, and at the moment, we're staying in that 53-day orbit.
0:04:47 > 0:04:50Now to me, if you're in a 53-day orbit rather than
0:04:50 > 0:04:53a two-week orbit, that seems like less data.
0:04:53 > 0:04:55It's actually not a massive amount of difference.
0:04:55 > 0:04:56We'll get exactly the same science
0:04:56 > 0:04:59and we'll be covering exactly the same regions of the planet.
0:04:59 > 0:05:00It will just take longer,
0:05:00 > 0:05:03so we're having to learn to be slightly more patient.
0:05:03 > 0:05:05So, what did you see from that first encounter?
0:05:05 > 0:05:07Well, one of the wonderful things about Juno's orbit
0:05:07 > 0:05:09is it's giving us a vantage point we have never,
0:05:09 > 0:05:13ever had before, the ability to look at the poles of Jupiter.
0:05:13 > 0:05:15What I'm going to show you now is one of those first-ever
0:05:15 > 0:05:18images of the South Pole of Jupiter.
0:05:18 > 0:05:20So you're seeing light being reflected from the day side
0:05:20 > 0:05:22just here, and the night side down here,
0:05:22 > 0:05:25and as we zoom into this image, you can see the incredible
0:05:25 > 0:05:29structures that we're seeing here at the South Pole.
0:05:29 > 0:05:32These are pinwheel storms that are presumably moving
0:05:32 > 0:05:35and migrating all over the South Pole itself, so this is the
0:05:35 > 0:05:38South Pole of Jupiter, but of course we saw the North Pole as well.
0:05:38 > 0:05:41Here it is, again in this incredible detail.
0:05:41 > 0:05:45If we just zoom in again, you see all of these pinwheel storms
0:05:45 > 0:05:48and cyclones that are taking place, no belt zone structure,
0:05:48 > 0:05:51but the thing I'm most excited about is what's going on up here.
0:05:51 > 0:05:54What you have is a cloud that's actually rising up from the night
0:05:54 > 0:05:58side of Jupiter and it's getting so high in the planet's atmosphere
0:05:58 > 0:06:03that it's catching the dying rays of the sun as the sun is going down.
0:06:05 > 0:06:08As well as the camera, that operates in visible light,
0:06:08 > 0:06:10Juno is equipped with a whole suite of instruments
0:06:10 > 0:06:12to probe the planet in other ways...
0:06:14 > 0:06:16..including its infrared imager
0:06:16 > 0:06:18that can penetrate Jupiter's cloud tops
0:06:18 > 0:06:20and reveal the vast scale of its aurorae.
0:06:22 > 0:06:25When we first saw this image, it really knocked our socks off.
0:06:25 > 0:06:26I'm not surprised.
0:06:26 > 0:06:29What you're looking at is the aurora at the South Pole of Jupiter,
0:06:29 > 0:06:33glowing because hydrogen ions are emitting their light
0:06:33 > 0:06:35as they're being bombarded by these electrons.
0:06:35 > 0:06:39It looks like a wall of fire, many times the size of the Earth.
0:06:39 > 0:06:42All of this incredible structure will be changing,
0:06:42 > 0:06:46ebbing and flowing over the course of just a few minutes.
0:06:46 > 0:06:47Amazing stuff.
0:06:47 > 0:06:50Now what I can show you next are the very first observations from
0:06:50 > 0:06:54the microwave instrument on board Juno that's allowing us
0:06:54 > 0:06:56to see down below the clouds.
0:06:56 > 0:06:59Now, this image on the right-hand side is what you're familiar with,
0:06:59 > 0:07:01it's the banded structure of Jupiter.
0:07:01 > 0:07:03We've got the red spot there, all of this looks very familiar.
0:07:03 > 0:07:05Absolutely, so this is light being reflected
0:07:05 > 0:07:07from the topmost cloud deck.
0:07:07 > 0:07:10These slices that you see on the left are probing deeper
0:07:10 > 0:07:13and deeper and deeper down into the interior depths.
0:07:13 > 0:07:14If you look at these,
0:07:14 > 0:07:18it's obvious that we are actually seeing banded structures still
0:07:18 > 0:07:23down in the interior of Jupiter, down 300km below these cloud decks.
0:07:23 > 0:07:26So what this means is that the surface that we're seeing
0:07:26 > 0:07:30is just the tip of the iceberg and that below that tip we're seeing
0:07:30 > 0:07:33an enormous circulation or atmospheric pattern that will
0:07:33 > 0:07:37keep atmospheric scientists going for years, trying to interpret
0:07:37 > 0:07:38what is actually taking place.
0:07:38 > 0:07:41Please come back again and tell us more about this amazing planet.
0:07:41 > 0:07:44- Will do, thank you. - Thank you very much.
0:07:44 > 0:07:48And that brings us to our second highlight of the year.
0:07:55 > 0:07:59At the end of August, just days before Juno's first close pass
0:07:59 > 0:08:04around Jupiter, news came of another tremendously exciting announcement.
0:08:07 > 0:08:10Now scientists are hailing a major discovery,
0:08:10 > 0:08:13a new planet which they've called Proxima B.
0:08:13 > 0:08:16At just four light years away, it's relatively close to us.
0:08:16 > 0:08:18It's roughly the same size as Earth,
0:08:18 > 0:08:21and because it's just the right distance away from its star,
0:08:21 > 0:08:25it could be the right temperature to have liquid water and possibly life.
0:08:27 > 0:08:30The planet was found orbiting Proxima Centauri,
0:08:30 > 0:08:32our closest neighbouring star.
0:08:32 > 0:08:35At just over four light years away, it's just close enough
0:08:35 > 0:08:39to imagine that we might one day be able to send a spacecraft there.
0:08:43 > 0:08:46Having a planet around Proxima is exciting and pretty much
0:08:46 > 0:08:51everyone who studies exoplanets has scrambled to have their say
0:08:51 > 0:08:53about what it must really be like.
0:08:54 > 0:08:58In some ways, the planet is very different from the Earth.
0:08:58 > 0:09:02It orbits just 7.5 million kilometres from its star -
0:09:02 > 0:09:06that's roughly 20 times closer than the Earth is to the sun.
0:09:07 > 0:09:11But because Proxima Centauri is so much cooler and dimmer
0:09:11 > 0:09:15than our sun, the planet could be a similar temperature to the Earth.
0:09:15 > 0:09:19But being so close to its star could also create other problems.
0:09:20 > 0:09:24For example, it was thought that Proxima was a violent star,
0:09:24 > 0:09:27sending stellar flares towards the planet,
0:09:27 > 0:09:30and making it an inhospitable place.
0:09:31 > 0:09:35But new research seems to show that it's no more violent than our sun.
0:09:37 > 0:09:38But there remain many unknowns.
0:09:38 > 0:09:42We've no real idea what the planet is like.
0:09:42 > 0:09:45We can't observe it directly and so everything we know
0:09:45 > 0:09:48we've had to infer by watching the gravitational effect
0:09:48 > 0:09:50that it has on its star.
0:09:51 > 0:09:54And so a French team have tried to work out the planet's
0:09:54 > 0:09:57characteristics by using comparisons with the planets
0:09:57 > 0:09:59in our own solar system.
0:10:01 > 0:10:05If it has a large metallic core and a rocky mantle,
0:10:05 > 0:10:06like Mercury does,
0:10:06 > 0:10:09then it's probably a little bit smaller than the Earth,
0:10:09 > 0:10:12but there are other, more exotic possibilities.
0:10:12 > 0:10:17It could be much bigger than the Earth, 1.4 times the size,
0:10:17 > 0:10:20in which case it would have to have a rocky core, surrounded by
0:10:20 > 0:10:24a mantle of ice, and excitingly, the model suggests that
0:10:24 > 0:10:28the entire planet would then be covered in a vast ocean, 200km deep.
0:10:31 > 0:10:33All this speculation is great fun,
0:10:33 > 0:10:37but what we really need are more observations.
0:10:37 > 0:10:41But those observations will be extremely challenging.
0:10:41 > 0:10:45The planet is too small and too faint to be directly imaged
0:10:45 > 0:10:47with current telescopes.
0:10:47 > 0:10:50And so we must wait for the next generation of instruments
0:10:50 > 0:10:53before we can understand its true nature.
0:10:53 > 0:10:56The story of Proxima B has a long way to run.
0:11:01 > 0:11:04Earlier this year we asked for your help to identify
0:11:04 > 0:11:07a new class of comet hidden in the asteroid belt.
0:11:07 > 0:11:11These main belt comets are similar to ordinary asteroids,
0:11:11 > 0:11:14apart from they occasionally sprout tails.
0:11:15 > 0:11:19Very little is known about these strange objects,
0:11:19 > 0:11:22but their tails are almost certainly produced by pockets of ice,
0:11:22 > 0:11:24vaporising as they are heated by the sun.
0:11:26 > 0:11:29That means that these main belt comets could represent
0:11:29 > 0:11:33a huge and previously unknown source of water in the inner solar system.
0:11:35 > 0:11:37But only a handful have been found,
0:11:37 > 0:11:40so we sent out a call to get you searching for them.
0:11:40 > 0:11:44We had a fantastic response and Sky At Night viewers have
0:11:44 > 0:11:48contributed to identifying over 340,000 images to date.
0:11:50 > 0:11:53And from them, you identified these two, which appear to be
0:11:53 > 0:11:58producing tails and which could be newly-discovered comets.
0:11:58 > 0:12:01The next step is to observe these objects
0:12:01 > 0:12:04through the 8.2-metre Subaru telescope in Hawaii.
0:12:04 > 0:12:07This will hopefully occur early next year and it will help
0:12:07 > 0:12:11the team to identify whether these really are main belt comets,
0:12:11 > 0:12:14and we'll bring you the results as soon as we have them.
0:12:24 > 0:12:27The Comet Hunters project shows the power and the potential
0:12:27 > 0:12:30of everyone to make new discoveries.
0:12:33 > 0:12:37If you're inspired to become a stargazer yourself,
0:12:37 > 0:12:40or if you're getting a telescope for Christmas, Pete is here
0:12:40 > 0:12:43with some tips on how to get the best results.
0:12:47 > 0:12:48Now, it's probably fair to say
0:12:48 > 0:12:50that astronomy isn't the cheapest of hobbies,
0:12:50 > 0:12:53but for a few hundred pounds you can get some pretty decent kit
0:12:53 > 0:12:55and there are plenty of manufacturers out there that
0:12:55 > 0:12:57make packages such as this.
0:12:57 > 0:13:00Now, here I've got a very sturdy tripod at the bottom
0:13:00 > 0:13:02to hold everything very steady.
0:13:02 > 0:13:05On top of that, I've got an equatorial mount head,
0:13:05 > 0:13:07and this one has a motor attached to it.
0:13:07 > 0:13:11Now this has the job of counteracting the Earth's rotation,
0:13:11 > 0:13:14so it keeps everything that I'm looking at through the eyepiece
0:13:14 > 0:13:16in exactly the same position.
0:13:16 > 0:13:19On top of that, I've got my telescope tube,
0:13:19 > 0:13:23and in this case, this is a 70mm refracting telescope.
0:13:25 > 0:13:29This is an ideal size to view the moon and deep sky objects,
0:13:29 > 0:13:32such as open clusters and galaxies.
0:13:32 > 0:13:34To align the telescope properly,
0:13:34 > 0:13:37it needs to be balanced on the mount.
0:13:37 > 0:13:40And the mount needs to be pointed as accurately as possible
0:13:40 > 0:13:44at the celestial pole, which is close to the North Star.
0:13:45 > 0:13:49Once you've got your telescope set up, you need to leave it
0:13:49 > 0:13:52for about an hour to cool down to the outside temperature.
0:13:52 > 0:13:56That will also allow your eyes to adapt to the darkness.
0:13:58 > 0:14:01And then you are ready to start observing.
0:14:01 > 0:14:04And what I'm going to line up on tonight is the Andromeda Galaxy,
0:14:04 > 0:14:05Messier 31.
0:14:05 > 0:14:08That's our nearest, largest neighbouring galaxy.
0:14:11 > 0:14:14The Andromeda Galaxy is located almost overhead
0:14:14 > 0:14:15during early evening
0:14:15 > 0:14:17to the north-east of
0:14:17 > 0:14:18the Great Square of Pegasus.
0:14:18 > 0:14:22Use the right-hand side of the W-shape constellation of
0:14:22 > 0:14:24Cassiopeia as a pointer to it.
0:14:24 > 0:14:26Point your scope at the galaxy,
0:14:26 > 0:14:30lining its elliptical haze up with the finder's crosshairs.
0:14:34 > 0:14:37If you want to take pictures of what you're observing,
0:14:37 > 0:14:41you can add an adapter ring that will connect most DSLR cameras
0:14:41 > 0:14:42to the telescope.
0:14:42 > 0:14:46But bear in mind that you'll have to rebalance the scope
0:14:46 > 0:14:48to take into account the weight of the camera.
0:14:49 > 0:14:53So, trying the ISO setting of between 400 and 1,600,
0:14:53 > 0:14:57the higher you go, the noisier the end result will be.
0:14:57 > 0:15:02Also an inexpensive shutter release cable like this is a great idea,
0:15:02 > 0:15:05because it allows you to take your pictures without
0:15:05 > 0:15:08touching the camera and wobbling the telescope.
0:15:08 > 0:15:12Now, for a tracking mount like this, exposures between,
0:15:12 > 0:15:15say, 30 and 120 seconds are possible.
0:15:15 > 0:15:18The key to success is to experiment.
0:15:19 > 0:15:23There it is, the Andromeda Galaxy, and beautiful it looks too.
0:15:23 > 0:15:25Look at that, there's so much detail in there.
0:15:25 > 0:15:28I've got the core, I've got the spiral arms which are really
0:15:28 > 0:15:30faint, sort of, going round the core,
0:15:30 > 0:15:35and I can see the dark dust lanes running through the galaxy as well.
0:15:35 > 0:15:40And I've got the satellite galaxies, M32 and M110, also in that shot.
0:15:40 > 0:15:45Loads of detail. And with a fairly basic set-up. It's amazing.
0:15:56 > 0:16:00Our third highlight of the year was announced way back in January.
0:16:00 > 0:16:05And it took both the scientific community and the public by surprise.
0:16:10 > 0:16:14A team of researchers from Caltech claimed that they had
0:16:14 > 0:16:15evidence for a ninth planet.
0:16:16 > 0:16:19Hidden in the outer reaches of our solar system,
0:16:19 > 0:16:22far beyond the icy realm of the Kuiper Belt.
0:16:23 > 0:16:27I set out to demonstrate just how extreme this planet's orbit was.
0:16:29 > 0:16:34On this scale, every centimetre is about 35 million kilometres.
0:16:35 > 0:16:38The Earth is 150 million kilometres from the sun.
0:16:40 > 0:16:42Pluto is 40 times further away
0:16:42 > 0:16:46and the outer edge of the Kuiper Belt is still further.
0:16:47 > 0:16:49But Planet Nine is far beyond that.
0:16:49 > 0:16:52At the point of closest approach in its orbit,
0:16:52 > 0:16:55it sits 200 times further from the sun than the Earth.
0:16:55 > 0:16:59That's a whopping 30 billion kilometres away from the sun.
0:17:01 > 0:17:03But unlike the other planets,
0:17:03 > 0:17:06the proposed orbit of Planet Nine is not circular.
0:17:08 > 0:17:11Its highly eccentric path takes it much, much deeper into space.
0:17:14 > 0:17:18At its furthest possible point, its aphelion,
0:17:18 > 0:17:22it could be as much as 1,200 times further from the sun than the Earth.
0:17:25 > 0:17:28On this scale it's 54 metres away.
0:17:29 > 0:17:33In reality it would be 180 billion kilometres from the sun.
0:17:35 > 0:17:37This discovery was enormous news,
0:17:37 > 0:17:41but there was one crucial stumbling block.
0:17:41 > 0:17:44No-one had actually seen Planet Nine.
0:17:44 > 0:17:48Its existence had only been predicted by computer models
0:17:48 > 0:17:53that had been built by Caltech astronomers Mike Brown and Constantine Batygin.
0:17:53 > 0:17:57They'd been trying to understand the unusual elliptical orbits of
0:17:57 > 0:18:01six distant objects out in the Kuiper Belt, seen here in pink.
0:18:02 > 0:18:05They found that the only way they could replicate these orbits
0:18:05 > 0:18:09was if there was a ninth planet orbiting far beyond Neptune.
0:18:12 > 0:18:15When I met Mike shortly after the announcement in January,
0:18:15 > 0:18:19he explained to me that the next challenge would be to find the planet.
0:18:21 > 0:18:25Clear sky, sort of. Where is it? Where's this planet?
0:18:25 > 0:18:28Well, we know its path across the sky.
0:18:28 > 0:18:32We know its orbit, so we know the path and the path across the sky goes from somewhere over here,
0:18:32 > 0:18:38up across here right through the middle of Orion and Taurus and then down south across this way,
0:18:38 > 0:18:40and then of course all the way back around.
0:18:40 > 0:18:44We actually also know that around Orion and Taurus is where it's
0:18:44 > 0:18:46the most distant from the sun.
0:18:46 > 0:18:48And we think that's where it is.
0:18:48 > 0:18:52We think that the places that are closer to the sun, it would be too bright, we would have seen it.
0:18:52 > 0:18:55I mean, we're not talking amateur telescopes here to find this.
0:18:55 > 0:18:58No, in the end it's going to take us some time on the biggest
0:18:58 > 0:19:02telescopes in the world, but with the biggest telescopes in the world,
0:19:02 > 0:19:05it is well within range and we'll be able to find it.
0:19:05 > 0:19:08- It's up there somewhere, probably.- Right there.
0:19:11 > 0:19:15Many astronomers are yet to be convinced, and so I recently
0:19:15 > 0:19:19caught up with Mike again to see how the search was going.
0:19:19 > 0:19:22- Hello?- Hey, Mike, it's Chris. How are you?
0:19:22 > 0:19:25- Good, Chris, how are you? - Yeah, nice to see you.
0:19:25 > 0:19:27So, look, I'm not going to waste any time.
0:19:27 > 0:19:29Have you found Planet Nine yet?
0:19:29 > 0:19:32- No.- Excellent, thank you! THEY LAUGH
0:19:32 > 0:19:34What progress do you have to report?
0:19:34 > 0:19:38My favourite one that we realised just this last summer is
0:19:38 > 0:19:41something that has been known since 1850 and has had
0:19:41 > 0:19:45no explanation, which is if you look at the planets of our solar system,
0:19:45 > 0:19:47all eight planets, they're in a disc.
0:19:47 > 0:19:51And that disc, the inclinations,
0:19:51 > 0:19:53the amount that they're tilted relative to each other,
0:19:53 > 0:19:55is less than one degree on average,
0:19:55 > 0:19:58so all eight planets are within this one little one-degree disc.
0:19:58 > 0:20:03The sun is tilted from that disc by about six degrees.
0:20:03 > 0:20:05It's really a strange thing.
0:20:05 > 0:20:10No-one has had a very good explanation for 160 years.
0:20:10 > 0:20:16And in fact it's been so unexplainable that most people don't even realise that it's true.
0:20:16 > 0:20:19So, we quickly sat down and did this calculation to figure it out
0:20:19 > 0:20:23and realised that our prediction of Planet Nine, and of where Planet
0:20:23 > 0:20:28Nine is, predicts about a six-degree tilt just like the tilt that we see
0:20:28 > 0:20:32and the exact direction that the sun is actually tilted.
0:20:32 > 0:20:36It was one of those remarkable moments where you do this
0:20:36 > 0:20:38calculation not knowing what the answer's going to be,
0:20:38 > 0:20:41and it comes out exactly what you were hoping it was going to be.
0:20:41 > 0:20:45So, lots of people are looking. Have you had sceptical reaction as well?
0:20:45 > 0:20:47Clearly not everyone's as sure as you are.
0:20:47 > 0:20:49What have the negative reactions been?
0:20:49 > 0:20:52Are people still questioning whether this is just chance, these alignments?
0:20:52 > 0:20:57Yeah, so, scientists as a rule are a sceptical tribe,
0:20:57 > 0:21:00and if you're going to be sceptical of anything,
0:21:00 > 0:21:05you should be sceptical of somebody claiming there's a planet out in the outer solar system,
0:21:05 > 0:21:08because people have been claiming this for
0:21:08 > 0:21:13approximately the last 165 years, and every time it's been a mistake.
0:21:13 > 0:21:16So, there are people trying very hard to show that it's not true.
0:21:16 > 0:21:21So far I haven't seen anything that has been convincingly showing
0:21:21 > 0:21:23that it's not really out there.
0:21:23 > 0:21:26Well, just before we let you go to get back to trying to find this
0:21:26 > 0:21:32thing for us, I'm going to make you bet, I think - next year, 2017?
0:21:32 > 0:21:38At the beginning of this year, I was cautious and I said five years.
0:21:38 > 0:21:43And now, I tell you, we have narrowed down the search area
0:21:43 > 0:21:46to such a small area with these calculations.
0:21:46 > 0:21:49I'm going to guess that next year...
0:21:49 > 0:21:51Next year's the year.
0:21:51 > 0:21:54I'm... I feel optimistic.
0:21:54 > 0:21:56OK, well, we'll talk to you then. Good luck.
0:21:56 > 0:21:59- All right, thank you very much. - Thanks, Mike.
0:22:01 > 0:22:03Mike certainly sounds convinced,
0:22:03 > 0:22:05even more than he did at the start of the year,
0:22:05 > 0:22:08and the evidence does seem to be piling up,
0:22:08 > 0:22:13so let's hope he's right and 2017 is the year that we find Planet Nine.
0:22:19 > 0:22:23Our fourth and final story comes from much, much deeper in space.
0:22:30 > 0:22:35Back in January, Planet Nine was described as potentially the discovery of the century.
0:22:35 > 0:22:38But then, just three weeks later, scientists at the Advanced
0:22:38 > 0:22:42LIGO instrument in the States made an even bigger announcement.
0:22:44 > 0:22:46- BBC NEWS HEADLINES:- Unravelling the secrets of the universe -
0:22:46 > 0:22:50the most important scientific discovery for a generation.
0:22:50 > 0:22:53Scientists in the United States have announced they have
0:22:53 > 0:22:55discovered gravitational waves.
0:22:55 > 0:22:57Einstein was right after all.
0:22:57 > 0:23:00Gravitational waves ripple through space and time.
0:23:01 > 0:23:04Gravitational waves were a key feature of Einstein's theory
0:23:04 > 0:23:05of general relativity.
0:23:05 > 0:23:08And the fact that they were discovered exactly a century after
0:23:08 > 0:23:11he predicted them strengthens his theory.
0:23:11 > 0:23:13But gravitational waves gives us so much more,
0:23:13 > 0:23:17cos they allow us to see some of the most exotic bodies in the universe,
0:23:17 > 0:23:20because what LIGO had detected was the collision
0:23:20 > 0:23:21between two black holes.
0:23:28 > 0:23:31Black holes are difficult to study by conventional means,
0:23:31 > 0:23:33because they do not emit any light.
0:23:36 > 0:23:38But the LIGO measurements suddenly gave us
0:23:38 > 0:23:42a way to observe exactly what happens when black holes collide.
0:23:45 > 0:23:481.3 billion light years away the two black holes,
0:23:48 > 0:23:5136 and 29 times the mass of the sun,
0:23:51 > 0:23:56have been orbiting each other in a binary system, before colliding
0:23:56 > 0:24:00with such force that they sent tremors rippling through space-time.
0:24:08 > 0:24:10But by the time they reached Earth,
0:24:10 > 0:24:13the waves had dissipated so much they caused a disturbance in
0:24:13 > 0:24:18LIGO's detectors that was only 1/1000th the width of a proton.
0:24:19 > 0:24:22A lot has happened since we brought you that first detection.
0:24:22 > 0:24:24In fact, just three months later,
0:24:24 > 0:24:27another collision between black holes was detected and then
0:24:27 > 0:24:30a third, but the signal for that one was
0:24:30 > 0:24:32a bit too weak to get full confirmation.
0:24:32 > 0:24:35But this collection of collisions gives us an indication that
0:24:35 > 0:24:38these events which we thought were rare may be relatively common.
0:24:42 > 0:24:47And these new discoveries are also causing us to reassess our ideas
0:24:47 > 0:24:50about the nature and formation of black holes.
0:24:50 > 0:24:54The data had revealed that some black holes spin at enormous
0:24:54 > 0:24:59speeds, 10% of the speed of light, much faster than we expected.
0:25:02 > 0:25:05And then there's a problem that the black holes detected in
0:25:05 > 0:25:09the first collision are far too massive to exist in a binary system.
0:25:14 > 0:25:18Black holes form from the collapse of massive stars at the end
0:25:18 > 0:25:19of their lifetimes.
0:25:21 > 0:25:24It had always been assumed that black hole pairs formed
0:25:24 > 0:25:25from binary star systems.
0:25:26 > 0:25:30But the black holes in the LIGO observations are so vast, they
0:25:30 > 0:25:34must have formed from stars that were too big to survive as binaries.
0:25:35 > 0:25:38They would have fallen into each other and merged long before
0:25:38 > 0:25:40they could have formed black holes.
0:25:41 > 0:25:45So, we need a new model to understand how black holes collide.
0:25:47 > 0:25:51It may be that instead of forming in a binary star system
0:25:51 > 0:25:53that the two black holes formed independently,
0:25:53 > 0:25:57maybe in a dense star cluster, then gravitated towards each other,
0:25:57 > 0:26:00forming a binary pair which then collapsed.
0:26:05 > 0:26:09What's really exciting about this gravitational wave discovery
0:26:09 > 0:26:13is that it lets us see things that were previously hidden.
0:26:13 > 0:26:17Instead of relying on light in looking only at things that shine,
0:26:17 > 0:26:21we have a whole new way to observe the universe.
0:26:21 > 0:26:25LIGO has just begun its second run, and detections are expected
0:26:25 > 0:26:29to come thick and fast over the coming months and years.
0:26:29 > 0:26:32We don't know what these next observations will reveal,
0:26:32 > 0:26:35but we do know that when people look back at this first discovery
0:26:35 > 0:26:39in 2016, they'll see it as a great moment in the history of
0:26:39 > 0:26:44astronomy, as transformative as the invention of the radio telescope.
0:26:46 > 0:26:50That brings us to the end of the four major stories we covered this year.
0:26:51 > 0:26:54But there have been many other exciting events
0:26:54 > 0:26:56that slipped by without fanfare.
0:26:56 > 0:26:58Two. One...
0:26:58 > 0:27:02In September we saw the launch of Osiris Rex, an ambitious
0:27:02 > 0:27:07new mission to collect a sample of an asteroid and return it to Earth.
0:27:07 > 0:27:09Elsewhere in the solar system,
0:27:09 > 0:27:12it's been a good year for discovering water.
0:27:12 > 0:27:16An ice volcano twice the size of Everest was found
0:27:16 > 0:27:18on the dwarf planet Ceres.
0:27:18 > 0:27:23Plumes of water had been detected erupting from Jupiter's moon Europa.
0:27:24 > 0:27:26And there's fresh evidence for the existence of
0:27:26 > 0:27:28a subsurface ocean on Pluto.
0:27:30 > 0:27:33Further afield, astronomers have discovered that there are ten times
0:27:33 > 0:27:38more galaxies in the observable universe than first thought.
0:27:38 > 0:27:39Some two trillion of them.
0:27:40 > 0:27:43One of them, Dragonfly 44,
0:27:43 > 0:27:47has been found to be made of 99.9% dark matter.
0:27:48 > 0:27:52Making it the largest dark matter galaxy ever observed.
0:27:53 > 0:27:552016 is coming to an end,
0:27:55 > 0:27:57but there's lots of exciting stuff for the New Year.
0:27:57 > 0:28:01Yes, we've got the launch of not one but two exoplanet missions,
0:28:01 > 0:28:02a total solar eclipse in the US,
0:28:02 > 0:28:06more from LIGO and I'm looking forward to Curiosity climbing
0:28:06 > 0:28:09the slopes of Mount Sharp, but what are you most excited about?
0:28:09 > 0:28:12Well, for me it is all about the end of Cassini. It's been an epic
0:28:12 > 0:28:15mission and now it's coming to an end, and it's going to be
0:28:15 > 0:28:18a grand finale as the spacecraft plunges into the depths of Saturn.
0:28:18 > 0:28:22- What a way to go.- Yeah, it's a shame it's got to end, but it will be spectacular.
0:28:22 > 0:28:25That's it from us from this year, but we'll be back in January,
0:28:25 > 0:28:26so you don't have long to wait.
0:28:26 > 0:28:29And in the meantime, don't forget to go to the website to check out
0:28:29 > 0:28:32this month's guide to the night sky.
0:28:32 > 0:28:35And, as usual, get outside and get looking up.
0:28:35 > 0:28:36Goodnight.