Mysteries of Uranus' Oddities Explained by Japanese Astronomers

upstart writes in with an IRC submission for chromas:

Mysteries of Uranus' oddities explained by Japanese astronomers:

The ice giant Uranus' unusual attributes have long puzzled scientists. All of the planets in our Solar System revolve around the Sun in the same direction and in the same plane, which astronomers believe is a vestige of how our Solar System formed from a spinning disc of gas and dust. Most of the planets in our Solar System also rotate in the same direction, with their poles orientated perpendicular to the plane the planets revolve in. However, uniquely among all the planets, Uranus' is tilted over about 98 degrees.

[...] How Uranus' unusual set of properties came to be has now been explained by a research team led by Professor Shigeru Ida from the Earth-Life Science Institute (ELSI) at Tokyo Institute of Technology. Their study suggests that early in the history of our Solar System, Uranus was struck by a small icy planet - roughly 1-3 times the mass of the Earth - which tipped the young planet over, and left behind its idiosyncratic moon and ring system as a 'smoking gun'.

The team came to this conclusion while they were constructing a novel computer simulation of moon formation around icy planets. [...] There is strong evidence Earth's own single moon formed when a rocky Mars-sized body hit the early Earth almost 4.5 billion years ago. This idea explains a great deal about the Earth and its Moon's composition, and the way the Moon orbits Earth.

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