First images of a comet with adaptive optics

Using the ADONIS adaptive optics system at ESO (La Silla, Chile), on 8 March 1996, we made the very first observation of a comet with adaptive optics. Comet C/1996 B2 (Hyakutake) has been imaged in the near-infrared (J, H, K bands at 1.2, 1.6 & 2.2 μm respectively). The achieved spatial resolution of ≈ 0.2″, has allowed us to isolate two distinct dust-colour regions in the immediate neighbourhood of the cometary nucleus. On a [J-H] colour index map, a bluer region has been detected in the sunward-facing hemisphere, while a redder one is located symmetrically in the anti-solar direction. The major dust component in the coma remains silicates. These new observations should help to constrain the current models for dust components in comets. They clearly demonstrate the feasibility of observing comets with adaptive optics systems. Future observations of comet Hale-Bopp should greatly benefit from this new technique.