NASA's Alan Stern said these planets are so far away from the sun that we haven't seen them yet:
Our old view, that the Solar System had nine planets will be supplanted by a view that there are hundreds if not thousands of planets in our Solar System. It could be that there are objects of Earth-mass in the Oort cloud (a band of debris surrounding our planetary system) but they would be frozen at these distances. They would look like a frozen Earth.So all we need to do is haul one of those babies into our orbit, defrost it, and start populating. Earth 2, here I come!
Beyond our solar system, millions more Earth 2s await. University of Arizona astronomer Michael Meyer, co-author of a study about extrasolar dirt-and-water worlds, told reporters:
Our observations suggest that between 20% and 60% of Sun-like stars have evidence for the formation of rocky planets not unlike the processes we think led to planet Earth. That is very exciting.Image from Guardian Unlimited.