What I am always amazed at is how freely they use the term "potentially earth-like" when all they can see from this distance is a small distortion of the light of the parent star as it is obstructed by the planet moving in front of it, from our point of view.
From this tiny reduction on light intensity they extrapolate the estimated (!) size of the planet, and it's distance from the main star. All they can probably tell is whether it is in the parent star's habitable zone, and how big it is.
The size, however, says nothing about the stuff this planet is made of. Sure, it is LIKELY that a planet roughly the same size as earth MIGHT be a rocky planet with a metal core, as ours is. Still, that doesn't mean it has an atmosphere, or could sustain one if somehow, in a distant future, we should actually manage to successfully terraform planets. It's also impossible to tell whether there is water on this planet or not.
Any astronomers here who can correct me? I have all my limited knowledge from documentaries.
Careful... you are assuming a bit too much here. "Habitable zone" does not mean "similar distance to their sun as Earth". Every star has a different habitable zone, depending on its radiation output. Bigger stars than our Sun have their habitable zone far out, thousands of lightseconds away, whereas M-Type Red Dwarfs might need an earthlike planet to have such a close orbit that it would be tidally locked like our moon... always facing the star with the same side because the gravity of the star does not allow the planet to rotate.
I believe the word "zone" gave it away already.
