JET-LIKE FEATURES NEAR THE NUCLEUS OF CHIRON

CONSIDERED as a comet, the object 2060 Chiron is unusual in two respects: it exhibits outbursts at very large distances from the Sun(1-3), and its nucleus is much larger than that of any other known comet(4,5). It is, however, similar in size to the recently discovered Kuiper-belt objects(6)-a population of objects with orbits beyond Neptune, which are a possible source of short-period comets. This has led to the conjecture that Chiron is related to these objects, but its chaotic orbit has brought it much closer to the Sun(7). Here we report observations of a recent stellar occultation by Chiron which permit the identification of several features associated with Chiron's coma. The observation of discrete, jet-like features provides evidence that the coma material originates from just a few, small active areas, rather than from uniform sublimation, and that the particles in at least one of these features have radii greater than 0.25 mu m. The observations also suggest the presence of material in the plane of Chiron's orbit and are consistent with a gravitationally bound coma, Finally, the present data, and those from a previous occultation(8), constrain the radius of Chiron to lie between 83 and 156 km.