The Mystifying Case of the Missing Planets
After the sun formed, the dust and gas left over from its natal cloud slowly swirled into the eight planets we have today. Small, rocky things clung close to the sun. Gigantic gas worlds floated in the system\u2019s distant reaches. And around countless stars in the galaxy, a version of this process repeated itself, forging plentiful planets in a spectrum of sizes \u2014 except, apparently, worlds just a tad bigger than Earth.