New information about Uranus’ dusty rings from Voyager 2 images

Uranus is surrounded by a complex ring system that includes a variety of tenuous structures composed primarily of dust-sized particles. These dusty rings were first seen in images obtained by the Voyager 2 spacecraft, but several of them were thought to only be detectable in a single Voyager image. It has therefore been difficult to compare these data to other observations of these rings and other dust populations. In particular, ground-based images obtained at near-infrared wavelengths in 2007 indicated that the location of the peak brightness of the innermost dusty ring (known as the zeta ring) had likely shifted outwards from where it was in one Voyager 2 image (de Pater et al. 2007 Science), but it was not clear whether this shift is associated with a change in the overall brightness of this ring. New investigations of the Voyager data have now revealed that the zeta ring is visible in many more clear-filter low-resolution Voyager images, spanning a relatively broad range of observing and lighting conditions. These data not only confirm that the location of the peak brightness in the zeta ring did indeed change between 1986 and 2007, but also indicate that the total amount of material in this ring also changed substantially over that time. Furthermore, these data allow the distribution of dust around Uranus to be more directly compared with the dust populations around the other giant planets, facilitating investigations of transport processes like atmospheric drag that should operate in all these different systems.