Dr. Katherine Volk

about 34 AU out to 150 AU.

This is the inclination of the plane that the orbits should be precessing around if we've accounted for all the mass in the solar system.

And it changes with distance, because you're a different distance away from the masses in the solar system.

And you get funky features like this, because there are resonances in the system, just like there were mean motion resonances between orbital periods.

You can get resonances here.

The rate that you're precessing around is almost exactly the same as Neptune's orbital precession rate, and that causes a resonant feedback.

So you can get features like that.

But this is a well understood problem.

This was worked out a long time ago, how to calculate this.

So we know what the answer should be, but what does the data actually tell us?

So this is the measured mean plane, these purple dots, for the Kuiper belt.

And this is the number of objects that went into it.

So we couldn't use all of the known Kuiper belt objects for this calculation.

We could only use a subset of them because we wanted to bin in distance.

So we had to have things where we actually know the distance reasonably well, which is a surprisingly small number of Kuiper belt objects.

There have been a lot of poorly observed objects.

And then we also can't have things that are in mean motion resonances with Neptune, because it violates some of the assumptions that went into calculating the predicted plane.

So we were left with just non-resonant things, which are these green dots over here.

So in this region, where the Kuiper Belt's behaving pretty nicely, we had about 620 objects to work with.

Then we had about 160 in the outer solar system, where things are starting to look like they're behaving less.