Our planet has its very own asteroid that leads our planet in orbit around the Sun. Discovered by NASA's space-based Wide-field Infrared Survey Explorer (WISE) mission and announced in a July 28, 2011 paper, 2010 TK7 is a special class of asteroids called Trojan Asteroids. These asteroids either follow or lead a planet in the same basic orbit around the Sun. They remain gravitationally stable which means their orbits do not change. Neptune, Mars, Jupiter and two of Saturn's moons share their orbits with Trojan asteroids. 2010 TK7 is estimated to be 1,000 feet across and 50 million miles from Earth.
Read More About It: http://www.nasa.gov/mission_pages/WISE/news/wise20110727.html
Sky Guy in VA
This artist's concept illustrates the first known Earth Trojan asteroid, discovered by WISE. The asteroid is gray and its extreme orbit is shown in green. Image credit: Paul Wiegert, University of Western Ontario, Canada