KN DESK: 31, May 2013; The asteroid that is going to zip past the Earth at nearly 6 million kilometers away tonight is not travelling alone. Nasa scientists tracking the asteroid with the giant Deep Space Network antenna in California have discovered that the asteroid has a small satellite or moon. The asteroid is about 2.7 kilometers in diameter. The newly found moon that orbits it is just 600 meters wide. Such a 'binary' or double system is rare but not unknown to space watchers. About 16 per cent of asteroids with diameters 200 meters or more are binary or even triple systems, a Nasa statement said. The closest approach of the asteroid occurs on May 31 at 1:59 pm Pacific (4:59pm Eastern / 20:59 UTC), which is about 4:29 AM Indian Standard Time. This is the closest approach the asteroid will make to Earth for at least the next two centuries. (AGENCIES)