It’s mind-blowing to think that a telescope, in orbit around the Earth, can detect the very faint dimming of a distant star when a planet passes in front. But as NASA’s Kepler space telescope is showing us, not only is it possible, very tiny worlds can be detected by using this method.

But how tiny is tiny?

NEWS: Mini-Mercury: Tiniest Exoplanet Discovered

Kepler-37b is the very definition of a tiny world and its detection is a testament to the scientists and engineers who designed Kepler’s sensitive optics. Orbiting its parent star some 210 light-years away, Kepler-37b could be considered to be a mini-Mercury.

Its dimensions are smaller than the smallest planet in the solar system (sorry Pluto, I’m looking at Mercury) and only a little bigger than our moon. The handy size chart released by NASA does a good job of comparing Kepler-37b’s dimensions. (But look at Kepler-37b’s big brother, Kepler-37d! What a whopper!)

Although Kepler-37b could be termed a “mini-Mercury,” it could also be called a “super-Pluto” (just a thought).