DISCOVERY OF THE CANDIDATE KUIPER BELT OBJECT 1992 QB(1)

THE apparent emptiness of the outer Solar System has been a long-standing puzzle for astronomers, as it contrasts markedly with the abundance of asteroids and short-period comets found closer to the Sun. One explanation for this might be that the orbits of distant objects are intrinsically short-lived, perhaps owing to the gravitational influence of the giant planets. Another possibility is that such objects are very faint, and thus they might easily go undetected. An early survey1 designed to detect distant objects culminated with the discovery of Pluto. More recently, similar surveys yielded the comet-like objects 2060 Chiron2 and 5145 Pholus3 beyond the orbit of Saturn. Here we report the discovery of a new object, 1992 QB1, moving beyond the orbit of Neptune. We suggest that this may represent the first detection of a member of the Kuiper belt4,5, the hypothesized population of objects beyond Neptune and a possible source of the short-period comets6-8.