Dr. Katherine Volk

There's a bunch of objects that were detected and then their orbits were never fit accurately and we lost them over time and we have no idea what kind of objects they are.

So just for comparison, that's about where we were in the asteroid belt, you know, like a hundred years ago in terms of number of known objects.

And that's going to be key to our next discussion.

So what kind of completeness are we looking at in terms of our outer solar system knowledge?

And it's kind of a sad comparison with the inner solar system.

So for asteroids, both near Earth and main belt, I think we've essentially probably observed all of the 10 kilometer ones.

I don't know the exact completeness rate.

For near-Earth asteroids, the estimate is we know 90% of the things that are about a kilometer.

So that's pretty good.

We have a very good inventory, and we know essentially all of the big ones.

For comparison, the smallest ever imaged Kuiper Belt object is 30 kilometers across.

And that's actually MU69, the second New Horizons flyby target.

And the only reason we detected that is because we spent quite a bit of Hubble time searching for it.

Because when you have spacecraft in the outer solar system and nowhere to send it, because we didn't know of any objects that were within the delta V, you can convince the Hubble Time Allocation Committee that it's a good idea to look for new objects.

So that's the smallest one we've ever detected.

For a more typical ground-based survey,

You're looking at 50 to 100 kilometers is a more typical newly observed object that is considered faint for the survey.

And we're still discovering plenty of dwarf planets in the Kuiper Belt population.

I think there were two or three just this year, things that are probably 500, 600, 700 kilometers across.

So we are not really approaching anything complete for these smaller populations.