Not really. But the 5-kilometer diameter asteroid 3753 Cruithne is one of a kind — at least a far as planet Earth is concerned. It orbits the Sun in a 1:1 orbital resonance with the Earth (this is space-talk for the fact that its orbit is just about exactly one year long).
The things I learn from Wikipedia. The upper illustration shows the orbits of the Earth and 3753 Cruithne from the vantage point of a stationary sun. The two make their closest approach (about 30 times the distance from the Earth to the moon) each November.
From Earth’s point of view 3-C (I’m tired of typing the full name) moves first toward and then away from us, and further oscillates between being farther away from, then closer to, the Sun.
The resulting motion, far from being random, follows a shape known to cosmologists by the highly technical terms “kidney bean-shaped” or “horseshoe.” This is the perspective of the second illustration.
There are other, more subtle effects as well. Gravitational attraction between Earth and C-3 increases and decreases as they approach and recede. The resulting tugs move C-3’s orbit by about half a million kilometers, and Earth’s by a whopping 1.3 centimeters, so the orbits as a whole move apart and together over a period of several hundred years. The next closest approach will be in July of 2292, so set your alarms.
The existence of 3-C was not known until the 1980’s. Alas for the science fiction writers and others who have postulated a second moon for Earth, this technically isn’t it, since 3753 Cruithne does not literally revolve around the planet. But it’s the closest thing we have.
cleve callison’s blog 
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