Dr. Katherine Volk

In fact, I think the only thing we can say definitively about the outer solar system census is that there are no gas giants out there.

We can say that, which has a good data point, and that comes from the WISE survey.

So this was a satellite that did an infrared all-sky survey.

So when you have things big enough, like Jupiter and Saturn, they have enough internal heat left over from their formation that they give off a significant amount of infrared radiation.

So you don't have to rely on the reflected sunlight like we do for the Kuiper Belt objects.

So they did an all-sky survey, and they looked through it for solar system objects.

And they decided that within 10,000, 20,000 AU, there are no Jupiters or Saturns lurking out there.

So at least we have one complete statement.

There are no Jupiters or Saturns in the outer solar system.

But that's really about the only thing we can say with certainty.

Because if we kind of look at the more, you know, the ground-based surveys that are looking in reflected light, this is a map.

So this is showing the sky in a projection.

This line here is the ecliptic plane, so the plane of the solar system.

This is the galactic plane, the plane of the Milky Way.

And things that are orange and yellow are areas of the sky that we have searched to reasonably faint magnitudes for moving objects in the outer solar system.

Where reasonably faint is something like 24th visual magnitude.

You can see that there aren't that many yellow and orange spots on the map.

Many more of them are kind of in the red and pink.

That's something like we have searched reasonably well to 20th or 21st visual magnitude.

And then purple is like 17th magnitude.