It's got a sun in the middle, little planets on the inside, bigger ones farther out. That's what most of them should look like, no?

We thought they should. In astronomy class (for any of us who took astronomy) they talked about a "frost line." That's a line, some distance from the sun, where it gets too cold to make rocky planets.

They said when a planetary system forms, the dust that's closer in, on the hot side of that line, melts into rocky minerals, forming solid balls, like Earth and Mars.

But farther out, on the frosty side, the dust stays gassy, mostly hydrogen compounds, swelling to gigantic size, like Jupiter, Saturn and Neptune.

Distance from the sun sculpts the neighborhood. That's why most planetary systems in the universe were supposed to look like us. Rocky planets in, gassy planets farther out.

Then we looked. And what did we discover?