Cruithne

[spiff]

Anybody know anything about what has been called "Earth's second Moon"?

[Skids]

It is the 5km wide Asteroid 3753.  It is locked into a 1:1 resonance with Earth which means it orbits the Sun in the same time the Earth orbits the Sun (I think) but on a different path.  The nearest it comes to the Earth is 1 Astronomical Unit (40 moon lengths).  There are another two asteroids also in 1:1 resonance with the Earth.

[Phantaxus]

this should be more than enough for you

 

http://www.astro.uwo.ca/~wiegert/3753/3753.html