The real facts about Uranus

Uranus is the seventh planet from the Sun and the third biggest (by diameter). Uranus is bigger in diameter but smaller in mass than Neptune. Uranus is composed mainly of rock and various ices, with only about 15% hydrogen and a little helium (in compare to Jupiter and Saturn which are mostly hydrogen). Uranus (and Neptune) is in numerous ways alike to the cores of Jupiter and Saturn minus the huge liquid metallic hydrogen envelope. It appears that Uranus does not have a stony core like Jupiter and Saturn but rather that its material is more or less consistently distributed.

Like the other gas planets, Uranus has bands of clouds that carry around rapidly. But they are very faint, visible only with radical image improvement of the Voyager 2 pictures (right). Recent observations with HST (left) show bigger and more pronounced streaks. Additional HST observations show even more activity. Uranus is no longer the ordinary boring planet that Voyager saw! It now seems understandable that the differences are due to seasonal effects since the Sun is now at lesser Uranian latitude which may because more pronounced day/night weather effects. By 2007 the Sun will be unswervingly over Uranus's equator.

Like the additional gas planets, Uranus has rings. Like Jupiter's, they are extremely dark but like Saturn's they are composed of quite large particles ranging up to 10 meters in diameter additionally to fine dust. There are 11 recognized rings, all very faint; the brightest is identified as the Epsilon ring. The Uranian rings were the first after Saturn's to be discovered. This was of great importance since we now know that rings are a common feature of planets, not a peculiarity of Saturn alone. Uranus' fascinating field is odd in that it is not centered on the center of the planet and is tilted almost 60 degrees with respect to the axis of rotary motion. It is almost certainly generated by motion at relatively shallow depths within Uranus.