Astrophysicist Ian O’Neill writes for Discovery News:
“Uranus is tilted 97 degrees to the vertical .. but how did Uranus come to be this way?
“Generally it is assumed that another planet must have collided with Uranus, pushing it off-kilter, but new computer models suggest a scenario that is far more elegant.”
:”Gwenaël Boué and Jacques Laskar from the Paris Observatory in France started out with the idea that Uranus may have once had a very large moon .. Through the gravitational “tugging” by the large moon’s mass, over the course of 2 million years Uranus may have wobbled to such an extent that it was pulled onto its side.”
Source: “Has the Mystery of Uranus’ Tilt Been Solved?“
Ian O’Neill, Discovery Now, Sun Dec 06, 2009