Science in GIFs: The eccentric orbit of Earth’s “second moon”
Though 3753 Cruithne is sometimes called our second moon, it does not actually orbit the Earth. Its eccentric orbit just happens to be in 1:1 resonance with ours, taking a year to go once around the Sun. From our frame of reference, Cruithne appears to be moving in a bean-shaped orbit about the Earth. This animation shows a similar orbit, and how the two motions can combine to give the illusion of the oddly shaped orbit. More
