Dec 25, 2018 I Paul Seaburn

New Look at Uranus Shows a Major Impact Made It Lopsided

Get your jokes ready, all of you “your-anus” mispronouncers. Your favorite planet to pun is back in the news with the announcement that its odd shape, lopsided position, lack of core heat and out-of-whack magnetic field may have all been caused by a (here comes one) major impact. Not only that, the impactor may have been the mysterious rumored Planet X that could be on a path to eventually come back and pound Uranus again (that’s the last one for now – it’s your turn).

"We have performed a suite of smoothed particle hydrodynamics (SPH) simulations to investigate in detail the results of a giant impact on the young Uranus. This cataclysmic event could explain Uranus' remarkable 98° obliquity and we also study the internal structure, atmospheric retention, and orbiting debris of the post-impact planet.”

In a presentation titled “How Uranus Fell Over: Consequences of Giant Impacts with High Resolution Simulations” presented at the recent American Geophysical Union Fall Meeting in Washington DC, Jacob Jacob Kegerreis, astronomy researcher at Durham University, updated his paper published this summer in The Astrophysical Journal. In his update, Kegerreis included a graphic image of the collision from the simulation, showing an Earth-sized planet colliding with Uranus, severely distorting its shape and scattering debris in all directuions – debris that would reform in the planet’s equally out-of-whack moons and the faint ring that still orbits it 3 -to-4 billion years later.

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NASA image of Uranus and its moons and rings

“Most of the material from the impactor's rocky core falls in to the core of the target. However, for higher angular momentum impacts, significant amounts become embedded anisotropically as lumps in the ice layer. Furthermore, most of the impactor's ice and energy is deposited in a hot, high-entropy shell at a radius of 3 R. This could explain Uranus' observed lack of heat flow from the interior and be relevant for understanding its asymmetric magnetic field.”

"Core into core” means it was a catastrophic direct hit, resulting a disruption in Uranus’ center that allowed the surface to be covered with enough ice that little or no heat escapes, making it the solar system’s most frigid planet. The simulations show that somehow the impactor managed to survive and, if it's the rumored Planet X, may someday return, possibly on the same disastrous path. (Side comment from Beavis and Butthead: "He said anisotropically -- hee-hee!")

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NASA wants a better look at Uranus

This latest update on the history and status of Uranus points out one more thing as space scientists lobby for budgets to send another robotic probe to get a better Horizon-to-Pluto-style look at the icy planet. To do that requires putting an end to the jokes, says NASA chief scientist Jim Green in his comments on the study – pointing out that it’s pronounced “YUR-uh-nus” like the Greek god of the sky.

“No one laughs when I say Uranus. They have to mispronounce it to get the chuckles.”

Sorry … not!

Paul Seaburn

Paul Seaburn is the editor at Mysterious Universe and its most prolific writer. He’s written for TV shows such as "The Tonight Show", "Politically Incorrect" and an award-winning children’s program. He's been published in “The New York Times" and "Huffington Post” and has co-authored numerous collections of trivia, puzzles and humor. His “What in the World!” podcast is a fun look at the latest weird and paranormal news, strange sports stories and odd trivia. Paul likes to add a bit of humor to each MU post he crafts. After all, the mysterious doesn't always have to be serious.

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