Well, as I have a moment I’ll tell you as Kepler realizes that there is a planet or not. It is a very simple technique that you can see in this video.
Just for a while you look and star images are taken by observing its brightness (months). If its brightness varies, that is, if not equal, it means that something is happening in front of the star and covering it, we will, as an eclipse, and something to cover the star a bit, all I can be is a planet or a fat rock fat.
This is valid and easier for small stars, where a brightness change is very noticeable. So the first planets to be “found” were in red dwarfs. In addition, it helps the planet’s orbit is very short and pass (in the months of observation) several times in front of the star.
It is a very simple (theoretically) method and the Kepler satellite, its features, its gyroscopes, it does very well. Unfortunately, the lifetime of the satellite is ready to close, though, because you have located a jug of “planets” (I think 3000), NASA plans to launch a similar mission to continue.
By the way, to see if it has an atmosphere and atmosphere has, when it passes in front of the star, the light curves of the front of the object (the planet) and passes through the atmosphere of the planet, allowing, for the color, diffraction, namely atmosphere and even if you know that up.
As I said, New Orizon, the satellite has been closely Pluto, in the past, now is the Kuiper belt to see if it catches something, just done that. After Pluto has been placed with the sun behind him to see if that atmosphere has this “planet”.