Uranus's most extraordinary feature is the tilt of its axis – almost 98° (or 82° if it is taken to be retrograde), so that the planet effectively spins around on its side. As a result, for part of its orbit, one pole continually faces the Sun while the other is in total darkness. Half an orbit later, the roles (and poles) are reversed. In between, the Sun rises and sets around the equator normally. For Uranus to be in such a position, it was almost certainly struck a formidable blow by another massive object. Since the plane containing its 13 rings (see Uranus, rings) and 27 known moons (see Uranus, moons) is similarly tilted, this impact presumably took place during or shortly after the accretionary phase of the planets.
http://www.daviddarling.info/encyclopedia/U/Uranus.html
Uranus remains mystery despite new discoveries
News-Times | 2004-11-30 | Robert Miller
Posted on 12/01/2004 9:25:34 AM EST by kahoutek
http://www.freerepublic.com/focus/f-chat/1291898/posts