Herein I correct the BBC, just to be polite:
Cruithne is very cool, but it's not a moon. The people who figured out what it's doing are very clear on this, but the BBC messed up, and lots of people are now quoting their error.
Cruithne doesn't orbit Earth--it orbits the Sun, doing weird horseshoes around Earth's orbit. This is one of the weirder known solutions to the three-body problem, one spotted mathematically long before it was observed out there in the real world. Now that they know what to look for, they've found two more asteroids in similar resonant orbits, but haven't published details yet.
See http://www.astro.queensu.ca/~wiegert/3753/3753.html for more information.
Cruithne is very cool, but it's not a moon. The people who figured out what it's doing are very clear on this, but the BBC messed up, and lots of people are now quoting their error.
Cruithne doesn't orbit Earth--it orbits the Sun, doing weird horseshoes around Earth's orbit. This is one of the weirder known solutions to the three-body problem, one spotted mathematically long before it was observed out there in the real world. Now that they know what to look for, they've found two more asteroids in similar resonant orbits, but haven't published details yet.
See http://www.astro.queensu.ca/~wiegert/3753/3753.html for more information.