2003–2007 and side-scattering geometry in 1986. Changes during the past 20 years in the distribution of dust, which is thought to predominate in the ring, cannot be ruled out. Other dust bands In addition to the 1986U2R/ζ and λ rings, there are other extremely faint dust bands in the Uranian ring system. They are invisible during occultations because they have negligible optical depth, though they are bright in forward-scattered light. Voyager 2'''s images of forward-scattered light revealed the existence of bright dust bands between the λ and δ rings, between the η and β rings, and between the α ring and ring 4. Many of these bands were detected again in 2003–2004 by the Keck Telescope and during the 2007 ring-plane crossing event in backscattered light, but their precise locations and relative brightnesses were different from during the Voyager observations. The normal optical depth of the dust bands is about 10−5 or less. The dust particle size distribution is thought to obey a power law with the index p = 2.5 ± 0.5. In addition to separate dust bands the system of Uranian rings appears to be immersed into wide and faint sheet of dust with the normal optical depth not exceeding 10−3. Outer ring system In 2003–2005, the Hubble Space Telescope detected a pair of previously unknown rings, now called the outer ring system, which brought the number of known Uranian rings to 13. These rings were subsequently named the μ (mu) and ν (nu) rings. The μ ring is the outermost of the pair, and is twice the distance from the planet as the bright η ring. The outer rings differ from the inner narrow rings in a number of respects. They are broad, 17,000 and 3,800 km wide, respectively, and very faint. Their peak normal optical depths are 8.5 × 10−6 and 5.4 × 10−6, respectively. The resulting equivalent optical depths are 0.14 km and 0.012 km. The rings have triangular radial brightness profiles. The peak brightness of the μ (mu) ring lies almost exactly on the orbit of the small Uranian moon Mab, which is probably the source of the ring’s particles. The ν (nu) ring is positioned between Portia and Rosalind and does not contain any moons inside it. A reanalysis of the Voyager 2 images of forward-scattered light clearly reveals the μ and ν rings. In this geometry the rings are much brighter, which