NASA has well as others have definted yesterday's "visitor" as a small asteroid.
The impace was over the ural mountain regions of the Russian Federation. the object is now estimated at 15 meters (50 feet)across and weighing in at 8000 tons. The explosion itself was estiamted to be 500 Klotons. It is a crowded neighborhood and while we should keep an eye on the skie, luckily this doesn't happen often!