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Uranus: Orbital Tilt from a Cataclysmic Collision

3 Jul 2018, 17:14 UTC
Uranus: Orbital Tilt from a Cataclysmic Collision
(200 words excerpt, click title or image to see full post)

Yesterday’s post about exoplanet obliquity inevitably brought our own system to mind, with the stark variations between planets like Earth (23 degrees), Uranus (98 degrees) and Mercury (0.03 degrees) serving as stark examples of how wide the variation can be. Thus seasonality has to be seen in context, and interesting questions arise about the effect of high degrees of obliquity on habitability. While thinking about that I received a new paper on Uranus that has bearing on the matter, with its attempt to quantify the ‘hit’ Uranus must once have taken.
After all, something accounts for the fact that the 7th planet spins on its side, its axis at right angles to those of the other planets, its major moons all orbiting in the same plane. Lead author Jacob Kegerreis (Durham University), working with Luis Teodoro (BAERI/NASA Ames) and colleagues modeled 50 different impact simulations in an attempt to recreate the axial tilt of this world. In play were the planet’s internal structure, rotation rate, atmospheric retention post-impact and the composition of materials injected into orbit by the event. Says Kegerreis:
“Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision ...

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