That plethora allows astronomers to start drawing conclusions about how common various sorts of planets are.

ECONOMIST: Another Earth?

Since 1994, researchers have confirmed the existence of more than 700 planets circling various stars, with more than 2, 000 additional candidates under study by astronomers around the world.

WSJ: Galaxy Hosts 100 Billion Planets, in New Estimate

Since 1994, researchers have confirmed the existence of more than 700 planets around various stars, with more than 2, 000 additional candidates currently under study by astronomers around the world.

WSJ: Galaxy Hosts 100 Billion Planets, in New Estimate

Eventually, you end up with four planets and a lot of rocks - of various sizes.

BBC: Mars' two-faced riddle 'solved'