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Uranus May Have Been Knocked Out of Alignment by a Huge Rogue Planet

Uranus already has self-esteem issues due it its name and the off-color mispronunciation the rest of the solar system (OK, just us) use. Now it looks like it will have to deal with taunts that it can’t defend itself from galactic invaders. A new study says it’s highly likely that the planet’s strange axial tilt and misplaced magnetic field was caused by a large rogue planet slamming into it four billion years ago. What’s up, Uranus? (Sorry.)

“We perform a suite of smoothed particle hydrodynamics simulations to investigate in detail the results of a giant impact on the young Uranus.”

Is this what it looked like?

In “Consequences of Giant Impacts on Early Uranus for Rotation, Internal Structure, Debris, and Atmospheric Erosion,” a study published in the Astrophysical Journal, author Jacob Kegerreis describes how he and fellow researchers at Durham University’s Institute for Computational Cosmology tackled the perplexing questions about Uranus’ odd traits, such as its 98-degree axial angle to its orbital plane and its rings and moons which all seem to orbit in the same orderly direction. Then there’s the puzzling magnetic field which seems to open and close daily, allowing deadly solar winds through.

“We ran more than 50 different impact scenarios using a high-powered super computer to see if we could recreate the conditions that shaped the planet’s evolution. Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision with an object twice the mass of Earth, if not larger, knocking it on to its side and setting in process the events that helped create the planet we see today.”

While simulations of objects hitting Uranus have been run before, this study uses the latest data and technology. These simulations showed that the rogue object most likely made a glancing impact rather than a direct hit, which explains why Uranus still has an atmosphere. That atmosphere is colder than expected because the simulations show debris from the impact could have formed a shell and trapped heat emanating from the planet’s core. The glancing hit could also explain why the debris spun off into rings and small moons that all travel in the same direction rather than in a helter-skelter multi-directional mess a direct hit would have caused.

The indirect blow would likely have made a less-visible shakeup inside Uranus, changing its shape and density in ways that would explain the funky, warped magnetic field and the axial tilt which is contrary to all other solar system planets.

NASA image of Uranus and its moons and rings

Unfortunately, while the simulation gives possible answers to the mysteries of Uranus and helps researchers better understand other ice giants being found in other solar systems, it leaves unanswered a bigger question … where did this rogue planet or giant object come from and will it come again? The model pictures its size at twice the size of Earth, which is smaller than speculations on the size of the rumored Planet X or Planet 9 or whatever you want to call it.

So many planetary mysteries … so little supercomputer time for running simulations. Perhaps these researchers need to focus more on rogue planets and get their heads out of Uranus. (Sorry.)

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Paul Seaburn Paul Seaburn is one of the most prolific writers at Mysterious Universe. 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. 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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