Third Moon around Earth.

According to the BBC we may have picked up a third natural satellite. It struck me as interesting that we don't know anything about the second one. From the article,

"Earth's second one is called Cruithne. It was discovered in 1986 and it takes a convoluted horseshoe path around our planet as it is tossed about by the Earth's and the Moon's gravity."

So naturally I wandered/wondered over to Google to find this article at Space.com. It's a great article describing the how asteroids temporarily become moons and after thousands of years wonder off again. From the article ,

"We found new dynamical channels through which free asteroids become temporarily moons of Earth and stay there from a few thousand years to several tens of thousands of years," said Fathi Namouni, one of the researchers, now at Princeton University.

"Eventually these same channels provide the moons with escape routes. So the main difference between the moon (we’ve always known) and ‘the new moons’ is that the latter are temporary -- they come and go, but they stay for a very long time before they leave."