Keck adaptive optics images of Uranus and its rings

We present adaptive optic images of Uranus obtained with the 10-m W. M. Keck II telescope in June 2000, at wavelengths between 1 and 2.4 mum. The angular resolution of the images is similar to0.06-0.09". We identified eight small cloud features on Uranus's disk, four of which were in the northern hemisphere. The latter features are similar to1000-2000 km in extent and located in the upper troposphere, above the methane cloud, at pressures between 0.5 and I bar. Our data have been combined with HST data by Hammel et al. (2001, Icarus 153, 229-235); the combination of Keck and HST data allowed derivation of an accurate wind velocity profile. Our images further show Uranus's entire ring system: the asymmetric c ring, as well as the three groups of inner rings (outward from Uranus): the rings 6 + 5 + 4, alpha + beta, and the eta + gamma + delta rings. We derived the equivalent I/F width and ring particle reflectivity for each group of rings. Typical particle albedos are similar to0.04-0.05, in good agreement with HST data at 0.9 mum. (C) 2002 Elsevier Science (USA).