Astronomers once thought our eight-planet solar system was pretty ho-hum: four small, rocky planets in the interior, four gas or ice giants farther out, and an asteroid belt in between. They expected the arrangement of most other planetary systems in our Milky Way galaxy to be about the same. But from what they’ve uncovered so far, it turns out that we could be the oddballs. Planets as big as Jupiter hug their home stars tightly--far more so, in fact, than Mercury hugs the sun. The orbits of planets Earth size or larger can be smaller than that of Venus. And some of the most common planet sizes in the galaxy--those between the size of Earth and Neptune--aren’t found in our solar system at all.