Uranus marches to the beat of its strange little drum.
While it shares many similarities with the other ice giant in our solar system, Neptune, it does have its own set of quirks.
And one of them is impossible to miss: its axis of rotation is so skewed that it could also be lying down. This is a gigantic 98 degree tilt from the orbital plane.
On top of that, it rotates clockwise – the opposite direction to most other planets in the solar system.
A new study has come up with a plausible explanation for this strange behavior: a moon is moving away from the planet, pulling Uranus on its side. And it wouldn’t even have to be a big moon. Something half the mass of our moon could do that, although a larger moon would be the potential contender.
The reason is explained in a research paper led by astronomer Mylene Silenvest of the National Center for Scientific Research in France. This article, which has not been peer-reviewed, has been accepted into the journal Astronomy and astrophysics and made available on a prepress resource arXiv.
Scientists have come up with models to explain this strange behavior, such as a huge body that collided with Uranus and I literally knocked him asideBut the most preferred Explanation he is space saver From little things.
However, this hypothesis raises questions that are difficult to explain: the disturbing similarities with Neptune.
The two planets have very similar masses, radii, rotation rates, atmospheric dynamics and compositions, and strange magnetic fields. These similarities suggest that the two planets originated together, and reconciling them becomes more difficult when planetary influences are added to the mix.
This led scientists to search for other explanations, such as oscillation that could be given by a Giant ring system or one giant moon Early in the history of the solar system (although there was a different mechanism).
But then, a few years ago, Saillenfest and his colleagues found something interesting Jupiter. Thanks to its moons, the gas giant’s tilt can go from the current 3% to About 37% in a few billion yearsThrough the outward migration of its moons.
Then they took a look at Saturn and discovered that its current inclination of 26.7 degrees could be a result of Rapid outward migration from its largest moonAnd Titan. They found that this can happen with almost no effect on the planet’s rotation speed.
This obviously raised questions about the most tilted planets in the solar system. So the team ran simulations of a hypothetical Uranian system to determine if a similar mechanism could explain its peculiarities.
It is not uncommon for moons to migrate. Our moon is currently moving away from Earth at a rate of 4 centimeters (1.6 in) per year. Objects rotating around an alternating center of gravity exert a tidal force on each other causing their rotation to gradually slow down. This, in turn, loosens the grip of gravity so that the space between the two objects expands.
Returning to Uranus, the team ran simulations with a range of parameters, including the mass of the hypothetical moon. They found that a moon with a minimum mass half the mass of Earth’s moon could tilt Uranus by about 90 degrees if it migrated more than 10 times the radius of Uranus at a rate greater than 6 centimeters per year.
However, in simulations it was more likely to produce a larger moon similar in size to Ganymede’s tilt and rotation seen on Uranus today. However, the minimum mass – about half of Earth’s moon – is about four times the combined mass of the moons of Uranus currently known.
Business also takes this into account. At a tilt of about 80 degrees, the moon It became unstable, resulting in a chaotic phase of its axis of rotation that ended when the Moon finally collided with the planet, “petrifying” the axial tilt and rotation of Uranus.
“This new image of Uranus’ tilt looks very promising to us,” write researchers.
“To our knowledge, this is the first time that a single mechanism has been able to tilt Uranus and petrify its rotation axis to its final state without causing a giant impact or other external phenomena. And part of the successful executions culminate in the location of Uranus, which appears as a natural consequence of the dynamics, “Hmm Complete.
“This image also looks attractive as a general phenomenon: Jupiter is about to start its tilt phase today, Saturn may be halfway there, and Uranus has completed its final phase, with its satellite destroyed.”
It’s unclear whether Uranus hosted a moon large enough and with a high enough migration rate to produce this scenario, and it would be difficult, the researchers say, to show through observations.
However, a better understanding of the current rate of migration of the moons of Uranus will go a long way to resolving these questions. If they were migrating at a high rate, it could mean that they were formed from the debris of the ancient moon after it was destroyed eons ago.
Bring This is a Uranus probe.
The search has been accepted Astronomy and astrophysics and available in arXiv.