Images of Neptune's ring arcs obtained by a ground-based telescope

Neptune has a collection of incomplete narrow rings, known as ring arcs, which should in isolation be destroyed by differential motion in a matter of months. Yet since first discovered(1) by stellar occultations in 1984, they appear to have persisted(2-6), perhaps through a gravitational resonance effect involving the satellite Galatea(6-8). Here we report ground-based observations of the ring arcs, obtained using an adaptive optics system. Our data, and those obtained using the Hubble Space Telescope (reported in a companion paper(9)), indicate that the ring arcs are near, but not within the resonance with Galatea, in contrast to what is predicted by some models.