First ground-based astrometric observations of Puck

The ten small inner moons of Uranus, discovered in 1986, have so far only been studied from space (Voyager 2, HST). The orbital elements derived from the observations indicate very weakly eccentric orbits for all of them but one (Ophelia). We present here the first ground-based astrometric observations of Puck, performed using an Adaptive Optics system. The long observing sequences permitted by ground-based facilities at ESO-La Silla, Chile (64.S-0289) revealed an eccentricity 100 times larger than previously believed. Such a disagreement with the actual theory may arise from the reduction itself based on the bright moons of Uranus, considered until now as precise astrometric references. To cite this article: P. Descamps et al., C. R. Physique 3 (2002) 121–128