“The number of planets will increase,” he added, “until about 2030 and then begin to stop. Another step will start, which will be to characterize more and more closely these planets. Detect more and more molecules, investigate the climate of these planets, et cetera. Another thing we could eventually do is to make the cartography of the planet—to make a multipixel image, to really see the continents. But this is 2050.”
The “book” of exo planet discoveries is being compiled and maintained by Jean Schneider, an astronomer at the Paris Observatory, who since 1995 has maintained The Extrasolar Planets Encyclopaedia of known exoplanets as well as those that are unconfirmed or controversial. Schneider advises caution about celebrating the 500th milestone as there is no consensus on what is a planet and what is a brown dwarf.