Hello it's Scott Manley here, today I want to talk about Planet X.
So Planet X is back in the news
you might've seen headlines that said "Planet X has been Discovered."
"There is another planet in the outer solar system."
Okay, hasn't been discovered.
What we do have is some really interesting evidence based upon observations of other objects that could be explained by the existence of another planet.
So let's rewind the clock a little.
Couple of years ago there was a discovery announced of a new object called 2012 VP113.
It was actually nicknamed Biden because of the VP in it's name.
And this was an object which the perihelion was 80 AU and its aphelion was way out over a couple of hundred AU.
So this in a highly eccentric orbit in the outer solar system.
Interestingly it's perihelion didn't come anywhere near Neptune.
Now Neptune's orbit is 30 AU
You instantly have a problem with these.
How do you put an object out into that orbit
because normally things get kicked into these orbits by having a close encounter with a planet
but if you're not coming down any closer than 80 AU you're not getting anywhere near Neptune to get kicked off.
Now the authors of this paper, they wanted to think about origins and so they looked at it
They also looked at another example of a similar object- one called Sedna.
Now Sedna goes out to yet further still, I believe.
And it was discovered by a guy called Mike Brown.
Who we'll hear more about later.
Now the authors of this paper, they said
Well wait a second, we noticed an interesting correlation
They noticed that the argument of perihelion of these two objects
were actually pretty close together, the orbits were roughly aligned.
Then they looked at some other objects that had a perihelion outside Neptune's orbit
and very large semimajor axis
So they looked for perihelion greater than 30 and semimajor axis greater than 150
so these were pretty eccentric orbits.
And they noticed that all of these were very much aligned in the sky unusually so.
If you just had these things floating out in space doing these orbits
for billions of years we would've expected them to kind've been randomly oriented across the sky
because of lots of just random perturbations.
To have them in one area of the sky said
Perhaps there's something shepherding them.
Regardless the original 2014 paper that was about the 2012 VP113
They kind've mention that maybe a planet could herd these things using something called the cosine mechanism
which is a fancy gravitational effect which occurs due to periodicities[?] basically.
Causes an oscillation of the orbit.
They didn't go too deeply into it
But last year, January 2015, a paper was published where somebody had gone really deeply into it.
They said "We think this could be due to two planets in the outer solar system herding these objects using the cosine mechanism.
Again, hey, great.
That was all very good.
And it got a little of attention.
But then this new paper by Mike Brown, the guy that discovered Sedna
He actually set out to disprove this hypothesis.
That was good science. Go and take a look some prediction and try to disprove it.
So first of all they pointed out that if it was a cosine mechanism you'd expect two groupings pointed in opposite directions.
We actually only see that in one direction.
Secondly he was concerned that of the 13 objects that some of them might've been affected by Neptune.
So what they did they took the data set of the 13 and they tested the orbit backwards and forwards
in time just to check to see if any of them could seriously be affected by Neptune.
So they actually threw away some of the objects and were left with six.
Then when they actually calculated probability of these things being aligned,
given they would expect them to be random, they came up with odds of something like
0.07% chance of this happening randomly.
So that was a relatively strong result.
So they kinda wound things forward and tried to come up with an object which would herd these things using some sort of mechanism obviously.
They came up with the idea of a 10 Earth-mass planet
with a perihelion of 200 AU and aphelion could be further out
This thing would orbit for tens of thousands of years they said for a single orbit.
And they've come up with an approximate idea of where to look in the sky.
But it's a huge area of the sky and something ten Earth-masses at that distance can be very cold, very hard to see.
A few years ago the WISE Spacecraft, Wide-field Infrared Survey Explorer, did photograph the entire sky in infrared,
and they excluded, they specifically excluded any planets that were larger than Saturn.
So we know it can't be as big as Saturn, which is fine because 10 Earth-masses is smaller than Saturn.
So anyway, they're gonna get telescope time, they're gonna look for it, maybe they'll find it.
Or maybe somebody else will come up with a better explanation for why these things appear aligned .
Maybe it is just a chance.
Maybe there's some sort of observational affect which we haven't realized.
These are all possibilities, and it would be good science to prove or disprove this thing.
Now if it was to be discovered, this wouldn't be the first planet to be discovered by a mathematical prediction.
That would be Neptune, of course.
You see, funnily enough if you think about it, there's only two planets that have been discovered
after the classical planets in the solar system, Uranus and Neptune.
Uranus was discovered with a telescope ,
Neptune was predicted by Le Verrier.
When he finally got somebody to look through a telescope at the region in the sky he wanted, they discovered it, that night.
So... 50%, half of the planets in our solar system have been discovered since the invention of the telescope.
have been discovered by mathematics
It's not such a ridiculous notion that the gravitational effects of an object could be used to infer it.
And therefore it's worth taking this very seriously but it's not worth saying there is a 10th planet out there absolutely for sure
Because it's a long way from being proved.
But it'll be a great journey to find out, there will be interesting math done, whatever
I'm Scott Manley, fly safe.