The planet Uranus is another solar system anomaly, where according to the NASA profile has an axial tilt of 97.8 degrees, also considered to be retrograde. This NASA summary "Uranus" suggests the current theory of a large planet-sized impact earlier in its history.

Does the planet-impact theory still hold true or have new accepted theories come to light?

Most of all, are there any results from any simulations available?

A note, this is posted as a separate question to my other question "What is the current accepted theory as to why Venus has a slow retrograde rotation?" as the axial tilt is significantly different.

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    $\begingroup$ Well, sorry to all responses but there is no accepted theory. A theory must be founded on axioms that make predictions that are testable against evidence. To that end we don't have any theories, just specilation. $\endgroup$ – AtmosphericPrisonEscape Mar 5 '16 at 0:53

Nasa.gov speculates that the most likely possibility is that an object with a mass close to that of Earth's collided with Uranus, causing it to rotate on its side from then on.

A recent test by Space.com suggests that "Planet Uranus Got Sideways Tilt From Multiple Impacts". These findings suggest that two or more smaller collisions probably occurred, asserting that the early solar system was probably more turbulent than most would think.

  • $\begingroup$ Note that all 5 of Uranus's major moons orbit "on their side" too...that is, their orbital inclination relative to Uranus's equator is very small. This is good evidence that something impacted (more accurately, flew thru) the proto-planet's accretion disk. The disk got re-oriented and the moons accreted afterwards. $\endgroup$ – DrZ214 Aug 26 '17 at 3:00

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