Look out for "Earthshine" brightening the shadowed region of the lunar disk close to the new moon phase.
Everybody knows that galaxies are large structures made of stars. That's a simple definition, and ignores the fact that galaxies also contain gas, dust, planets, moons, comets, asteroids, etc., and of course, dark matter. But one type of galaxy is mostly made of dark matter, and they're difficult to detect.

