Uranus is lopsided and there's a new scientific theory why

Uranus is lopsided. I know it, you know it and science knows it. The question is, how did it get like that?

The common theory is that a long time ago something smashed into Uranus, causing it to spill onto its side and remain there ever since.

But a new hypotheses suggests that the rings of Uranus may have something to do with it.

Yes, Uranus has rings.

The seventh planet from the sun is orientated 98 degrees from the orbital plane of the solar system.


Astronomers Zeeve Rogoszinski and Douglas Hamilton of the University of Maryland, reckon the planet’s rings may have something to do with it. Uranus’ rings are faint, but they may once have been as strong as Saturn. In fact, it may have been large enough to cause the planet to wobble on its axis like a spinning top.

‘If Uranus harbored a massive circumplanetary disk at least three times the mass of its satellite system while it was accreting its gaseous atmosphere, then its spin precession rate would increase enough to resonate with its own orbit, potentially driving the planet’s obliquity to 70°,’ they explained.

Known in astronomy circles as ‘precession’, this phenomenon works with the orbit of the body around the sun – the ‘orbital precession’ – to generate an axial tilt over time. In Uranus’ case, this could have caused it to tip over millions of years.

Rogoszinski and Hamilton produced computer models that calculated a 70-degree tilt over the course of Uranus’ lifetime.

‘Although we can generate tilts greater than 70 degrees only rarely and cannot drive tilts beyond 90 degrees, a subsequent collision with an object about half the mass of Earth could tilt Uranus from 70 to 98 degrees,’ they explained in their research, which has been published in The Astrophysical Journal.

‘Minimising the masses and number of giant impactors from two or more to just one increases the likelihood of producing Uranus’s spin states by about an order of magnitude.’

At the moment this remains just a theory – nobody really knows how Uranus got so lopsided.

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