Dr. Katherine Volk

So we really haven't done a great job in the southern sky here.

And then there are whole areas of the sky that we've been avoiding, which I will come back to later.

There's a lot of gaps here, and we haven't searched the whole sky to nearly deep enough to be sure that there aren't even things, you know, Neptune-sized in the outer solar system.

You know, we can say for sure that they're probably not lurking in these yellow fields, but there is a lot left to be done.

So now I'm going to get to the evidence that's been in the news a lot lately about potential planets in the outer solar system.

Although, disclaimer here, because someone already said it on Twitter,

They wouldn't be planets under the IAU definition, because there's Kuiper Belt objects all over the place.

So anything that's discovered out here would be a planetary mass object that hadn't cleared its orbit of stuff.

So disclaimer, I'm going to say planet.

I don't really care, but it wouldn't probably technically be a planet.

So I'm going to be talking about two different things, and they both touch on some research that's been done here at U of A. So first I'm going to talk a little bit about this Planet 9 that's been proposed, this big 10 Earth mass planet.

And then I'm going to talk about a more modest planet in the outer solar system that is a result of some research I did with Renu Malhotra here.

will address Planet 9.

So when we looked at these plots earlier, showing the orbits of all the known Kuiper Belt objects, you might have noticed that it doesn't look totally uniformly distributed in space.

There is maybe some clustering going on.

And some of this clustering was actually first noticed in 2014.

Some researchers who were doing some Kuiper Belt surveys were plotting up their data, as we like to do, and they were plotting them up in orbital elements.

So this is the easy one to understand, just average distance from the sun and closest approach to the sun.

And these things in the corner are kind of classical Kuiper Belt objects, nearby scattering objects.

These things out here kind of got nicknamed extreme Kuiper Belt objects because they're really far from the sun on average, and they don't really approach that close to the planets.