From the Gizmodo synopsis (which I will shorten too):
In a research paper called "The population of natural Earth satellites", astronomers say that Earth has a second moon at any given time. While these moons are small, the scientific implications of this discovery are phenomenal.
From the Technology Review article linked below:
|image via http://www.inrumor.com/|
But this was not an object of ours. Instead, 2006 RH120, as it became known, turned out to be a tiny asteroid just a few metres across--a natural satellite like the Moon. It was captured by Earth's gravity in September 2006 and orbited us until June 2007 when it wandered off into the Solar System in search of a more interesting neighbour.
2006 RH120 was the first reliably documented example of a temporary moon.
Source -> http://gizmodo.com/5869840/ via Cornell & https://www.technologyreview.com/blog/arxiv/27425/
Earlier links about the Moon -> http://www.dannyfinnegan.com/2011/11/moon_19.html & http://www.dannyfinnegan.com/2011/08/was-our-moon-result-of-2-smaller-moons.html