This is a… well, it’s pretty self-explanatory, really. Unlike most of the images collected here, it’s got its own description printed right on it. These are alien planets, a classroom poster depicting three basic types of planets like those we’ve discovered orbiting around distant stars.
The most interesting thing about this poster is that it’s very new, and it comes from the collections of the Institute of Physics, a British charity which creates educational supplies for teaching students of many levels about astronomy, energy, motion, and the building blocks of matter.
There are whole lesson plans there, handouts, magazines, and all sorts of stuff besides posters like this one.