Planet 9 from Outer Space The Sky at Night


Planet 9 from Outer Space

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When I was growing up, there were nine planets in the solar system.

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Then poor old Pluto got the boot, and we went down to eight.

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Now scientists claim they have found a new ninth planet

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orbiting far beyond Pluto.

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Tonight, The Sky At Night investigates

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the case for Planet Nine.

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On 20th January, two astronomers from this university,

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Caltech, in Pasadena, southern California,

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made an extraordinary announcement.

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They claimed they had compelling evidence that a new, as yet unseen, planet

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was orbiting the sun, far beyond the existing planets.

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So far this is a theoretical discovery. The planet's

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existence has been predicted by computer models.

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But if it does exist, it throws up many questions.

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Where is it? What does it look like?

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And most crucially, how did it get there?

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We'll be talking to astronomers here in California,

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and in the UK, to answer those questions and find out what

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a discovery of Planet Nine would mean for our understanding of the solar system.

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But first, let's put Planet Nine in context,

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and see how it fits in to our understanding of the rest of the solar system.

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This is what we thought was the extent of the solar system

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for thousands of years.

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And it's restricted to the planets we can see with the naked eye.

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So in the centre, of course, we have the sun, then Mercury,

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Venus, Earth, Mars,

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Jupiter. And 1.5 billion kilometres from the sun sits Saturn.

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And this is all we thought there was until the 18th century.

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Since then, the solar system has gradually expanded.

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In 1781, Uranus was discovered.

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Followed in 1846 by Neptune.

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Tiny Pluto was added in 1930,

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pulling the edge of the solar system out to 5.9 billion kilometres

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away from the sun.

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Pluto was counted as a planet for over 70 years.

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But now we know it is just one object in a huge doughnut-shaped

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belt of billions of icy bodies

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and comets called the Kuiper belt.

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It was thought that the Kuiper belt marked the outer edge of the realm of the planets.

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But now it seems that might not be the case.

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For some of us, it's an extraordinary thought,

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but many astronomers have long suspected there may be

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other planets lurking in the dark expanse beyond the Kuiper belt.

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And we're getting the first evidence that suggests

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they may be right.

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To get a feel of just how far away Planet Nine is, if it exists,

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we need to plot its position in relation to the rest of the planets.

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On this scale, every centimetre is about 35 million kilometres.

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The Earth is 150 million kilometres from the sun.

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Pluto is 40 times further away,

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and the outer edge of the Kuiper belt is still further.

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But Planet Nine is far beyond that.

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At the point of closest approach in its orbit, it sits

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200 times further from the sun than the Earth.

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That's a whopping 30 billion kilometres away from the sun.

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But unlike the other planets, the proposed orbit of Planet Nine is

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not circular.

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Its highly eccentric path takes it much, much deeper into space.

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At its furthest possible point, its aphelion,

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it could be as much 1,200 times further from the sun than the Earth.

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On this scale, it's 54 metres away.

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In reality, it would be 180 billion kilometres from the sun.

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And because the orbit is inclined by 30 degrees to the

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rest of the solar system, it means it's also above,

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or below, the plane of the rest of the planets.

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It seems almost unbelievable that there could be a planet

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so far out in the solar system.

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A mysterious world.

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Ten times more massive than the Earth...

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..on a orbit so long, it takes between 10,000

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and 20,000 years to complete one lap of the sun.

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But how was the discovery made?

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Chris drew the...short straw and flew to California to find out.

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One of the key people in the Planet Nine story is an astronomer

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here at Caltech. He's got history

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when it comes to changing our views of the solar system.

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Ten years ago, he was instrumental in demoting poor old Pluto.

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He even wrote a book about it. His name is Mike Brown.

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Brown's speciality is the Kuiper belt.

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In 2003, he discovered Eris, a Kuiper belt object bigger

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than Pluto,

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a discovery that was instrumental in Pluto's demotion.

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A month later, he co-discovered Sedna.

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This was the first of what became six unusual Kuiper belt objects

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that have been found with highly eccentric orbits that take them

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far out into space.

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They were six of the most distant objects ever

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found in the solar system.

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It was studying their orbits that led Brown to the

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idea that there might be another planet out there.

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So the story starts with the outer bits of the solar system, the Kuiper belt.

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What we found is that the most distant objects that are part

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of the Kuiper belt, so these ones that come into the Kuiper belt

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but swing out really far, the very most distant ones,

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if you look at their orbits, all of their orbits are pointing off

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in one direction, instead of being randomly distributed around the sky.

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So how tight is that alignment?

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The ones that we know for sure that are aligned are six objects.

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And they are aligned within about a 107-degree swath of the sky.

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-And that's what?

-Something like this.

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OK, and it's not just the alignment in direction as well,

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the orbits have other things in common.

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So, first you see the alignment in direction.

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Then you realise that these six very most distant objects are all

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tilted in the same direction downward and a little bit to the side.

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They are within about seven degrees of being in the same

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skewed plane of each other.

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And the combination of those two is what really shows

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you that there is something strange going on.

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You could get the six of them lined up, just due to chance,

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it's about a 1% chance you would get it due to chance. 1%, you know,

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it's a small number, but it's not that small of a number.

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But if you take also the fact that they're tilted

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like that, that's another approximately 1% chance.

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So it's about a 0.01% chance that this is all just randomly aligned.

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So is that what got your attention and got you working on the problem?

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That was the big clue that something is going on in the outer solar system.

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This was an extraordinary finding.

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The tight clustering of the six orbits might have been caused by the

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gravitational influence of something massive in the outer solar system.

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For Mike Brown, the question now became, what was out there

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and how could he find it?

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Working down the corridor from Mike is theoretical astronomer

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Konstantin Batygin. Mike and Konstantin have worked together for ages,

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and it always helps to have a friendly theorist on hand.

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And so Mike popped in to see if Konstantin could help with his problem.

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Konstantin's expertise is building computer models of planetary systems.

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-Hey, how's it going?

-How are you? Yeah, nice to see you.

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'And so Mike challenged him to build a computer model of the solar system

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'that would replicate the strange orbits of the six Kuiper belt objects.'

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When you started looking into this problem of these strange

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orbits, I know a planet wasn't the first thing you considered.

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-Indeed, yes.

-What else could have caused this effect?

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We had a whole slew of explanations

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that we decided to look into first. You know, so gravity of

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the Kuiper belt, so the mass of the disc itself

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holding itself together in a coherent fashion.

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All the bodies pulling on each other, essentially.

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That's right, to create almost a fluid-like effect.

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As it turns out, the Kuiper belt doesn't have enough material

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for this to be relevant. If it was 1,000 times more massive,

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that model would have some pull.

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We looked into whether or not a passing star could perturb

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the structures, leave this long tail of orbits that we are now

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here to observe.

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Such encounters don't happen very often,

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and the alignment would go away over time,

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so this would have had to be recent.

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And there is no sign of a very nearby star that has just done this.

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That's right. So I think that's a very uncomfortable route to go.

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And so with all of that out the way, you start to think about planets.

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We were careful to ensure that we're not chasing a red herring here.

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That this data is indeed real, the alignment is not some observational bias,

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it's not...it can't be a coincidence. All of that.

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Before going down the path of introducing additional

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planets into the solar system.

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When he started adding planets to his models, Batygin experimented

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with thousands of possible orbits - until he found one that

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replicated the strange orbits of the six unusual Kuiper belt objects.

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Suppose the orbit of Neptune is about this big.

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-OK.

-Most conventional Kuiper belt objects,

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Pluto included...

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..have orbits that

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sort of hug the orbit of Neptune and are oriented every which way.

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But importantly, if you look at the whole Kuiper belt from afar,

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it looks like a more or less axisymmetric disc.

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This rule of thumb is broken when you look at the most distant orbits.

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So these are the famous, the now famous six?

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That's right. If you look at the now famous six,

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they all tend to swing out into the same overall direction.

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So your simulation's predicted a nice elongated,

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distant Planet Nine orbit.

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Planet Nine has a sort of similar sized orbit,

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but it is facing the wrong way.

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You might as well draw the planet on. Go on. We haven't seen it yet, but just for satisfaction.

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The planet, I am pretty sure, is in this part of its orbit.

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-Cos otherwise we would have found it.

-We would have found it.

-Right.

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-So there's our planet.

-There's our planet. It's fascinating.

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Most of the time, the objects are on opposite sides of the solar system.

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They are completely unaware of each other throughout most of their orbits.

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It is only when they come around at

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-perihelion...

-When they are closest to the sun.

-When they are closest to the sun,

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they temporarily interact. And the mechanism, of course,

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is just gravitational interactions, and that's what maintains this lock step.

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So every time they come around, they get this kick? Or every two times...

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No, it gets complicated. For some orbits, it's every

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33 times of this orbit per 19 times of this orbit.

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But, fundamentally, it's not too different from tugging on something

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repeatedly in a coherent way.

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Batygin's model had passed the first test. It had successfully

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replicated the orbits of the famous six.

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But there was another, unexpected effect.

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The model also predicted a second set of Kuiper belt objects,

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with even stranger orbits.

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Trouble was, they didn't seem to exist.

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The biggest twist to the whole story came when our

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numerical models consistently would generate orbits

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that looked more or less like this.

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-So sort of coming in and out of the blackboard here.

-That's right. They are on their sides.

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They are perpendicular to the plane of the solar system.

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This is just so weird. You know, the fact that the simulation is producing these

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orbits that should be perpendicular, they should be readily

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observable. And the fact that we don't know of them is big trouble.

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So it's not just that they might be there. They have to be there.

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We initially thought of this as counter evidence to the existence of the planet.

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Fine, it explains alignment,

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but it also predicts stuff that's clearly not there.

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This was the key moment where we looked at it and said, "This makes no sense."

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But then I started looking more carefully at the other

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objects in the dataset that I had not been paying much

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attention to in the last couple of years.

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There are five of these objects on perpendicular orbits that I didn't...

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I remember when one of them was discovered a few years ago

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and thinking, "That's just weird." Nobody had any explanation for them.

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And I said, "Konstantin, I'm going to go and plot these right now

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"and we're going to see where they are. And if they're sitting at these two spots right here,

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"my head's going to explode." And we plotted them.

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One of them is right here,

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four of them are exactly right here where we predicted. And we both sat

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there and stared at that, and I think my jaw hit the floor.

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It really was an honest, blind prediction of something we didn't know was there.

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And that...that... When I look at those object on those wings,

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and then I see those aligned objects, too,

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I...think I'm really pretty convinced

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it's really out there.

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If Planet Nine does exist, it would be a remarkable discovery.

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The first new planet to be found in our solar system in 170 years.

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That isn't to say it was completely unexpected.

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Because there are places we have found planets

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that are similar to Planet Nine.

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I went to University College London to meet exoplanet expert

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Professor Giovanna Tinetti.

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Hello, Giovanna.

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Giovanna, if Planet Nine does exist,

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it seems to have some very exotic characteristics, compared with the rest of our solar system.

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In your work in exoplanets, have you seen anything similar to

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these characteristics out there?

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We're talking about an object that is about tens times

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the mass of the Earth.

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These king of objects are classified as super-Earths, which is

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a very exotic name. The NASA Kepler satellite tells us

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basically that these are among the most frequent objects in our galaxy.

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The fact that we didn't have any objects of this particular size was a bit puzzling,

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in a certain sense. But if Planet Nine does exist, then of course we are ticking the box

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and we also have our own super-Earth.

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-So we had one missing, and now it looks as if we've got one.

-Exactly, exactly.

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But Planet Nine, if it's out there, is a whopping 200 astronomical units

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away from Earth - at its closest approach.

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So, that just seems an awful long way away.

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Have you got examples of planets that far away from their sun?

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Actually we do. And what you see now is

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GU Psc b, which is located at 2,000 astronomical units from its star.

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So that's the further reaches of Planet Nine, potentially.

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-This is a real image, by the way.

-I know. The fact you can actually take an image like this is amazing.

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-It's really very cool.

-OK.

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So, we've looked at the size, we've looked at the distance

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from its local star.

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But now it's also a very eccentric orbit.

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-And that seems quite exotic for our solar system.

-It definitely is.

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Most of the planets in our own solar system are orbiting in orbits

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which are almost circular.

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But actually, out there, we are seeing planets that are orbiting in extremely

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elliptical orbits. And we have some examples, like

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this planet that is called HD 80606b.

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And, as you can see from this picture, we have planets

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out there that are orbiting in very elliptical,

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what we call eccentric, sort of orbits.

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So, if Planet Nine does exist, it is not as exotic as we perceive it to be.

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Because there are lots of other examples out there that are similar to the

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-characteristics of Planet Nine.

-You're right, Maggie, and if Planet Nine were proposed

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and discovered before extra-solar planets were found,

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probably we would dismiss this case, saying, "This is way too eccentric,

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"this is way too odd.

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"We can't have a planet like this."

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And the fact that, on the contrary, now we know that

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planets like this can indeed exist is really making

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the case for Planet Nine even more interesting.

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-Well, thank you very much, it's been fascinating speaking to you.

-It was a pleasure.

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In theory, there is no reason why Planet Nine should not be out there.

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But there is only one way to prove its existence.

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And that is to directly observe the planet.

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Mike Brown took Chris to the famous Griffith Observatory to look

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at the skies above LA and to point out

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where he thinks Planet Nine is.

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OK, well, clear sky. Sort of.

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Where is it? Where is this planet?

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Well, we know its path across the sky, we know its orbit,

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so we know the path. And the path across the sky

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goes from somewhere over here, up across here, right through the middle of Orion and

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Taurus, and then down south across this way, and then of course all the way back around.

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We actually also know that around Orion and Taurus is where

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it is the most distant from the sun.

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And we think that that is where it is. We think the places that are closer

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to the sun, it would be too bright, we would have seen it already.

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OK. So, in some sense, you're already getting some observational

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data on the star. You know where it isn't.

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And you know other things as well.

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The other thing that we would know is that if it is too big,

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if it is the size of Saturn or Jupiter, it would have been

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detected by the WISE spacecraft a couple of years ago.

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They did a survey of the whole sky, looking for things that move,

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and we now know that there is nothing as big as Jupiter or Saturn

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out to many, many times the distance of where we think Planet Nine is.

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So it has to be small, small meaning the size of Neptune

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or maybe a little bit bigger.

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And it has to be pretty far away still, and somewhere off from here.

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And pretty faint. We're not talking amateur telescopes here to find this.

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No, in the end, it is going to take us

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some time on the biggest telescopes in the world.

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But with the biggest telescopes in the world, it is well within

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range, and we'll be able to find it.

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-It will be exciting.

-Yes.

-So, I know you're looking for it.

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Lots of other people will as well, I'm sure they will now.

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Does it bother you who is going to find it?

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I would love to find it myself. I would love to have that moment which

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I've gotten to have before on these big objects in the Kuiper belt,

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like Eris, where you see it and for a moment you are the only person

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in the history of humanity who has seen this object so far away.

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I would love that, I will not lie.

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At the same time, I want it to be found.

0:19:170:19:21

And so if someone else finds it first

0:19:210:19:25

because they were searching hard for it and helping us out on the search,

0:19:250:19:29

yes, I will feel, my heart will sink a little bit, but I think

0:19:290:19:34

that will be overcome by the fact I'm so excited it was found.

0:19:340:19:38

-It's up there somewhere, probably.

-Right there.

0:19:380:19:41

One of the big questions about Planet Nine that we will have to

0:19:430:19:46

answer if people are to take the claims seriously is,

0:19:460:19:50

how did it get to its current orbit?

0:19:500:19:53

To get to the bottom of that question, I've come to

0:19:530:19:56

Queen Mary University of London to meet Professor Richard Nelson.

0:19:560:19:59

Richard, what's the problem with the proposed orbit of Planet Nine?

0:20:000:20:04

Well, it's very difficult to form a planet on an orbit like that.

0:20:040:20:06

We believe, according to current models, that it would take

0:20:060:20:09

almost the age of the solar system itself to form

0:20:090:20:11

-a planet all that far out.

-Because it has to accrete onto the body.

0:20:110:20:14

That's right. The accretion process which brings small

0:20:140:20:17

agglomerations of material together and builds larger and larger objects,

0:20:170:20:21

leading eventually to a planet all the way out there just takes far too

0:20:210:20:24

long because it's moving around very, very slowly and there's a very low density

0:20:240:20:28

-of material there as well.

-So, if it didn't form out there,

0:20:280:20:31

at the outer limits of the solar system, where did it form?

0:20:310:20:34

Well, our best guess is that it probably formed among the existing giant

0:20:340:20:37

planets - Jupiter, Saturn, Uranus and Neptune. So, there

0:20:370:20:40

are theoretical models already which indicate that if you run

0:20:400:20:43

computer simulations of the early solar system and its evolution, and

0:20:430:20:47

you have a dynamical instability, having a fifth planet there actually

0:20:470:20:50

helps those models reproduce what we see in the solar system today.

0:20:500:20:53

-So that fifth planet could be Planet Nine?

-It could be Planet Nine, which is no longer

0:20:530:20:57

-there but orbiting further out.

-So, what are we seeing here?

0:20:570:21:00

What we are seeing here is a computer model of the early stages of the solar system.

0:21:000:21:03

But with five planets. So the white planet there is Planet Nine.

0:21:030:21:07

The other planets are Jupiter, Saturn, Uranus and Neptune.

0:21:070:21:09

-You'll see the planets are going around on circular orbit.

-As you'd expect.

-As you'd expect.

0:21:090:21:14

They're all interacting, they're all perturbing one another.

0:21:140:21:16

But Planet Nine, in this simulation, is a bit too close to Saturn when it starts.

0:21:160:21:20

And at some point, we're going to see it have an encounter which gives it

0:21:200:21:24

quite a dramatic little kick, and you will see it change.

0:21:240:21:28

-There it goes.

-That's right, so you see that. And this keeps going, on and on.

0:21:280:21:32

Jump forward, you can see the planet's orbit has expanded a lot,

0:21:320:21:35

and there you have a very eccentric and a very inclined orbit.

0:21:350:21:38

Does that do it? Does this give us the orbit of Planet Nine?

0:21:380:21:41

Unfortunately not, because Planet Nine has an orbit where the closest approach to the sun

0:21:410:21:44

is about 200 or 300 astronomical units away.

0:21:440:21:47

So, as you will have seen here, Planet Nine keeps coming

0:21:470:21:50

back into the inner solar system

0:21:500:21:52

and continues to interact with the giant planets there.

0:21:520:21:54

Eventually, one of those encounters will be strong enough to throw it out of the solar system.

0:21:540:21:58

How can you stop it from pinging out into the galaxy?

0:21:580:22:01

If Planet Nine is actually proven to be there, it's going to tell us

0:22:010:22:04

something very interesting and important about the origin of our solar system.

0:22:040:22:07

So, what we've looked at so far is a solar system forming in isolation.

0:22:070:22:11

But now let's imagine that the solar system formed within a star cluster.

0:22:110:22:15

If we look out within the galaxy, we see that stars do tend to

0:22:150:22:18

form within groups and clusters of stars.

0:22:180:22:20

If Planet Nine was thrown out onto one of these very eccentric orbits

0:22:200:22:24

while the star cluster was still there, then gravitational

0:22:240:22:27

perturbations from the star cluster could have caused Planet Nine to

0:22:270:22:30

change its orbit when it was its most distant position from the sun.

0:22:300:22:33

So, I have a simulation which shows that here.

0:22:330:22:35

When it goes out on this orbit this time round, it's not

0:22:350:22:38

going to come back in any more. There's going to be

0:22:380:22:40

an interaction with a nearby star that changes the shape of the orbit.

0:22:400:22:43

Woo! So, suddenly it expands outward

0:22:430:22:45

and stops going back into the inner solar system.

0:22:450:22:48

So, that's what saves it from being ejected from the solar system.

0:22:480:22:51

So, a lot of your model does seem to tie in with

0:22:510:22:53

the evidence we're seeing for Planet Nine. It can explain the huge orbit, the inclined

0:22:530:22:58

orbit and why it's still there and not out there in the galaxy.

0:22:580:23:01

That's right. That's why I said at the beginning there, I think proving that

0:23:010:23:04

Planet Nine is present within our solar system, with the orbit suggested, would also indicate

0:23:040:23:09

very strongly that our solar system didn't form in a lonely place,

0:23:090:23:12

but was part of an earlier star cluster.

0:23:120:23:14

-Pretty fantastic stuff.

-Wonderful.

-Thank you, it's been fascinating.

0:23:140:23:18

A pleasure.

0:23:180:23:20

And that leaves one final question.

0:23:200:23:23

What sort of planet is Planet Nine?

0:23:230:23:26

And what are the conditions like so far out in space?

0:23:260:23:30

At the far reaches of its orbit, the sun would appear tiny.

0:23:310:23:35

Just a point of light.

0:23:350:23:38

But it would still be the brightest star in the sky.

0:23:380:23:42

Although the sun would be a million times dimmer than it is here

0:23:420:23:45

on Earth, it would be 1,200 times brighter than Venus appears to us.

0:23:450:23:51

That far from the sun is very cold.

0:23:530:23:55

Some estimates have suggested it could be below -250 Celsius.

0:23:550:24:01

As for the qualities of the planet, we don't really know.

0:24:010:24:04

The computer models suggest it should

0:24:040:24:07

be ten times more massive than Earth.

0:24:070:24:10

But it could take different forms.

0:24:100:24:12

One possibility is that Planet Nine could have been ejected

0:24:130:24:16

from the inner solar system early in its development,

0:24:160:24:19

when it was just the core of a giant planet.

0:24:190:24:22

This would make it predominantly rocky and icy.

0:24:220:24:25

Now, with ten times the mass of Earth, it would be about twice

0:24:250:24:28

the diameter. And it would probably appear to be a dark,

0:24:280:24:32

pinkish red in colour.

0:24:320:24:33

But if the planet was ejected when it was more fully formed,

0:24:350:24:38

then it would have a chance to build up the gassy layers,

0:24:380:24:41

like Neptune and Uranus.

0:24:410:24:43

Then it would be much less dense, and so bigger.

0:24:430:24:46

Maybe four times the diameter of Earth.

0:24:460:24:49

It's thought the planet may have an atmosphere rich in hydrogen

0:24:500:24:54

and helium.

0:24:540:24:55

In these cold temperatures,

0:24:560:24:58

it's likely it will appear as a bland, featureless sphere.

0:24:580:25:03

Unless the planet is still producing some internal heat, in which

0:25:030:25:06

case we may see structure in the atmosphere.

0:25:060:25:10

Clouds of methane ice, ammonia and even water ice.

0:25:100:25:15

It all seems so exciting, and yet despite the possibilities,

0:25:180:25:23

so far Planet Nine is no more than a prediction in a computer model.

0:25:230:25:26

And they have been proven wrong before.

0:25:280:25:30

So, very unscientific question.

0:25:330:25:36

But the one that keeps coming up.

0:25:360:25:38

How sure are you that this exists?

0:25:380:25:40

Oh, one quadrillion percent.

0:25:400:25:43

HE LAUGHS

0:25:430:25:44

-You've got an unscientific question, but a scientific answer.

-CHRIS LAUGHS

0:25:440:25:47

-Right back at you.

-But as a theory, you believe your models?

0:25:470:25:50

Actually, we try very hard not to believe our models.

0:25:500:25:53

But look, if this thing is not out there,

0:25:530:25:55

if the search comes up empty, then the outer solar system

0:25:550:25:58

has some really, really substantial explaining to do.

0:25:580:26:02

And you've ruled out the other explanations, right?

0:26:020:26:05

At least for me, it's difficult at this point to argue for a

0:26:050:26:08

solar system that makes sense without Planet Nine.

0:26:080:26:12

Mike, what about you?

0:26:120:26:13

So, I'm slightly lower than a quadrillion percent.

0:26:130:26:18

The human brain is really good at seeing patterns.

0:26:180:26:21

When I can't sleep at night, it's because I am worried

0:26:210:26:26

that we saw a pattern and made up an explanation.

0:26:260:26:30

And then as more observations...

0:26:300:26:34

come in, the pattern disappears. I don't think it's going to happen,

0:26:340:26:37

I'm actually very convinced. But that doesn't mean I sleep all through the night.

0:26:370:26:42

I sleep all through the night.

0:26:420:26:45

I am really eager to see it, to confirm it, to learn what it is like,

0:26:450:26:49

to see if it has moons and rings.

0:26:490:26:51

I just want to know all these things.

0:26:510:26:54

And do you have any sense of what that will feel like?

0:26:540:26:56

-You know, I bought a cigar...

-CHRIS LAUGHS

0:26:560:26:59

..about a year and a half ago and it's still sitting in my desk.

0:26:590:27:03

You know, every time something dramatic happens, I always forget to smoke it.

0:27:030:27:08

So maybe I won't forget...that time.

0:27:080:27:11

I'm going to go and buy a good bottle of champagne, and I'm going to put

0:27:110:27:15

it in my office, put it in the fridge in my office, so keep it

0:27:150:27:17

cold. And when it happens, we're just going to drink it right then.

0:27:170:27:21

And between now and the cigars and champagne,

0:27:210:27:24

while we are waiting for the discovery, what are you two working on next?

0:27:240:27:28

We are looking for the planet,

0:27:280:27:30

but we are also looking for more of these objects that are aligned

0:27:300:27:33

or perpendicular, that aren't aligned or perpendicular, to prove

0:27:330:27:36

ourselves wrong. If anyone is going to prove us wrong,

0:27:360:27:39

we would rather do it ourselves than to have someone else do it.

0:27:390:27:42

We are trying very hard to prove ourselves wrong.

0:27:420:27:44

-It's an exciting time.

-It is. Let's hope it gets more exciting.

0:27:440:27:47

-Thanks a lot.

-Thank you.

0:27:470:27:49

Today's been incredibly exciting. The team's belief in Planet Nine is contagious.

0:27:520:27:57

And I've become increasingly convinced that it really is out there

0:27:570:28:01

somewhere in the outer wastes of the solar system.

0:28:010:28:04

I'm sure I'm not the only one. There will be teams

0:28:040:28:06

and telescopes from across the world racing to be the first to see it.

0:28:060:28:10

And if it's found, when it's found, it will be THE astronomical

0:28:100:28:14

discovery of the century.

0:28:140:28:16

That's it for this programme.

0:28:180:28:19

Don't forget, check out February's star guide on the website.

0:28:190:28:22

Next month, we'll be looking at the top five photographs

0:28:220:28:25

of the solar system ever taken.

0:28:250:28:27

But in the meantime, get outside and...get looking up.

0:28:270:28:31

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