Uranus Tilting 98 Degrees May Be Due to a Moon Migrating Away from the Planet

by Alex Falls

The ice giant planet Uranus has several attributes that have long puzzled scientists. Including a usual rotational axis. But experts think they might have found an explanation for why its axis is so skewed it might as well be lying down.

The theory states a mysterious moon could be migrating away from Uranus. Which might have pulled the planet over onto its side giving it a sharp tilt of 98 degrees from the orbital plane. And it wouldn’t even need to be a big moon. Something half the mass of our own moon could have done it, although a larger moon would be the more likely contender.

The strange tilt is not the only thing unique about Uranus. It also rotates clockwise, which is the opposite direction from most of the other planets in our Solar System. Research into this phenomenon suggests the planet’s strange behavior started when a massive object roughly double the size of our planet hit Uranus. An impact significant enough to cause the planet to tilt.

The cataclysmic collision could have shaped the planet into how we observe it today. Including its freezing temperatures. However, it does not explain what its neighboring planet, Neptune, shares so many similarities. They share similar masses, rotation rates, atmosphere dynamics and compositions, and unusual magnetic fields. 

Scientists Try to Explain What’s Unique to Uranus

Scientists set out to find an explanation for this difference. They found a promising lead when observing the behavior of Jupiter. The gas giant has many moons in its orbit, and their outward migration is slowly shifting its slight. They found similar patterns with Saturn and the migration of its largest moon, Titan.

This led the team to perform simulations of a hypothetical Uranian system to determine whether a similar mechanism could explain its strange behavior. They found that a hypothetical moon with a minimum mass of around half that of Earth’s moon could tilt Uranus towards 90 degrees if it migrated by more than 10 times the radius of Uranus at a rate higher than 6 centimeters per year. 

Researchers released a statement regarding their findings. Saying, “This new picture for the tilting of Uranus appears quite promising to us. To our knowledge, this is the first time that a single mechanism is able to both tilt Uranus and fossilize its spin axis in its final state without invoking a giant impact or other external phenomena.”

“The bulk of our successful runs peaks at Uranus’s location, which appears as a natural outcome of the dynamics,” the statement continued. “This picture also seems appealing as a generic phenomenon: Jupiter today is about to begin the tilting phase, Saturn may be halfway in, and Uranus would have completed the final stage, with the destruction of its satellite.”

The paper detailing these findings is still awaiting peer review, but it has been accepted into the journal Astronomy & Astrophysics.