Dr. Katherine Volk

Neptune's at 30.

We call those the classical Kuiper belt because that's kind of what was envisioned when the Kuiper belt was first proposed.

But then of course there are higher eccentricity, scattering, and then there's a few other categories of scattering or extreme or detached Kuiper belt objects.

If we just take out the classical ones for a moment.

The scattering things get out to very large distances from the Sun, but their close approach is still kind of in Neptune's neighborhood, where they can still have strong gravitational interactions, which is part of how they got scattered out.

So that's kind of broadly speaking the two types of orbits we have out in the Kuiper Belt.

And if we now make this sort of plot for all of the known KBOs as of a few months ago, we can see this bundle of these circular, roughly circular classical belt, and then all of these scattering and even some really extremely distant Kuiper belt objects that we will come back to later.

So that's just the really brief overview of the Kuiper belt to give you some orientation.

But now I want to talk about how did we actually discover all of these things out in the Kuiper Belt?

How do we know they're there and what kind of orbits they're on?

So when we're looking for new solar system objects, what we're doing is we're scanning the night sky for anything that's moving against the background stars.

So this is an animation showing a near-Earth asteroid discovery from Space Watch, which is run here in this department.

You can kind of see it.

It's right here.

moving right through there as we blink through the images.

And then this other animation here is showing the planets Jupiter and Saturn over an 11-month span.

So we're going to talk about some of the features of this motion.

But first, just to understand why things are actually moving against the background stars.

So part of that motion is due to orbital motion around the sun.

Everything that's in orbit in the solar system is moving.