Dr. Katherine Volk

And what that looks like, if you were to be sitting on a, like looking down and riding the carousel with Neptune, is that Pluto's gonna come to perihelion once over here,

go around once over here and back.

And this is a resonance in the physics sense where there's a restoring force kind of like a pendulum where Pluto wanders a little bit out of the resonant configuration but then gets tugged back in.

And there's lots of objects in the Kuiper belt that are in resonance with Neptune like this.

So it would be perfectly reasonable if there was another large planet out in the outer solar system for some of these extreme objects to be in resonance with that planet.

And in fact, that's an active area of research amongst many groups right now, because if you can identify what resonances they're likely to be in, because there's this geometry relationship between where the objects have their closest approach to the sun and where the planet is, you can use these resonant configurations to nail down where you should be looking for this object.

So you could plot reasonable sky maps to say, you know, these black areas are areas where the resonant geometry would be all wrong.

So the planet shouldn't be there.

So there's lots of people looking into this.

But it's kind of a tricky problem because technically there's an infinite number of possible resonances.

And the orbits of the extreme hyperbolic objects are not super well known, so their orbital periods are fairly uncertain.

But active area of research.

One other thing that Planet 9 could explain is the tilt of the Sun's spin axis relative to the orbits of the planets.

So if we looked at this darker line here as the average orbital plane of all the planets in the solar system, you would expect the Sun's spin axis to be exactly 90 degrees relative to that plane.

But it's actually something like 7 degrees away from that perfect orientation.

And so that's kind of been a mystery for a while.

And if you stuck a 10 Earth mass planet at 600 AU, it could tilt the planets relative to the sun's spin axis, nicely to explain this.

So not really evidence for the planet, but it would be a neat part of the story.

So there's lots of these little things that might be pointing toward this 10 Earth mass planet.

My opinion is maybe it's there.