Uranus' tilted axis, unusual properties due to collision with icy planet: Study

Japan-based researchers have claimed that Uranus was struck by a small icy planet, about 1-3 times the Earth's mass, which tipped it over and left behind its "unusual" 27 moons and ring system. Researchers reached this conclusion while constructing a simulation of moon formation around icy planets. Uranus' spin axis is tilted by 98°, meaning it spins on its side.