this astroid isn t moving slowly. it s careering towards earth at unimaginable speed. it s got astronomers across the world very excited. this is the closest approach by an astroid that large. reporter: this is the path traveling inside the moon s orbit coming within just 200,000 miles from earth. it will be moving straight at us from one direction and go straight away from us in the other direction. reporter: the dense carbon rock has been tearing around space for thousands of years it will be a rare chance to view such a beast from the ground. radar telescopes are preparing for the fly by on tuesday night. if it hit earth, it would have the power to hit london or create a 70 foot tsunami.