OK, so it's dark.
Some dark matter is in the form of planets orbiting stars.
Small, low luminosity stars such as red dwarfs may account for some dark matter because although they shine, most are too faint to be seen from Earth. Other dark matter is in the form of brown dwarfs, which are wannabe stars that, while bigger than planets, didn't quite make to stardom. They give off heat mostly from internal gravitational compression, but they do not glow in visible light and do not undergo fusion. Predicted a few decades ago, brown dwarfs are so faint that they have only recently been observed. One possible candidate WIMP are the neutrinos that pervade the Universe in staggering numbers, although the question of their mass is still not totally resolved.