When this view was obtained, Uranus was nearly on the opposite side of the sun as seen from Saturn, at a distance of approximately 28.6 astronomical units from Cassini and Saturn. An astronomical unit is the average distance from Earth to the sun, equal to 150 million kilometers. At their closest, the two planets approach to within about 10 astronomical units of each other.
The planets Uranus and Neptune are sometimes referred to as 'ice giants' to distinguish them from their larger siblings, Jupiter and Saturn, the classic 'gas giants'. The nick names derives from the fact that a comparatively large part of the Uranus and Neptune consists composition of water, ammonia and methane, which are typically frozen as ices in the cold depths of the outer solar system. On the outher side Jupiter and Saturn are made almost entirely of hydrogen and helium, with smaller percentages of these ices.