Asteroids

ASTEROIDS Giuseppe Piazzi at Palermo, Italy discovered the first asteroid on Jan. 1, 1801. At first Piazzi thought that he had discovered a comet; however, after the orbital elements of the object had been computed it became clear that the object moved in a planet-like orbit between the orbits of Mars and Jupiter. Piazzi was able to observe the object only until February 11, and, as no one else was aware of its existence, it was not re-observed …

…the dinosaurs some 65 million years ago. This extinction may have been triggered by an explosion resulting from the impact of an asteroid measuring roughly 10 km in diameter. Some investigators believe that a cometary body rather than an asteroid may have caused such an explosion. Fortunately, collisions of this sort are rare. According to current estimates, a few asteroids of 1-km diameter collide with the Earth every 1 million years. So keep your eye out for one ;)