Uranus marches to the rhythm of its strange little drum.
While it shares many similarities with the other ice giant in our solar system, Neptune, it has a number of quirks.
And one of them is impossible to miss: its axis of rotation is so oblique that it could even be lying down. This is a gigantic 98 degree inclination from the orbital plane.
It also rotates clockwise, the opposite direction to most other planets in the solar system.
A new study has provided a plausible explanation for this strange behavior: A moon is moving away from the planet, dragging Uranus on its side. And it shouldn’t be a big moon either. Something of the mass of half of our moon could do it, 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 This article, which has not been peer-reviewed, was accepted in the journal Astronomy and astrophysics and made available on a prepress resource arXiv.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 put it asideBut the most preferred Explanation he is save space From little things.
However, this hypothesis raises difficult questions to explain: the disturbing similarities to Neptune.
The two planets have very similar masses, radii, rotational speeds, dynamics and atmospheric 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 look for other explanations, such as the wobble that could be given by a Giant ring system or one giant moon Early in the history of the solar system (although a different mechanism existed).
But then, a few years ago, Saillenfest and his colleagues found something interesting Jupiter. Thanks to its moons, the inclination of the gas giant can go from the current 3% to About 37% in a few billion yearsThrough the outward migration of its moons.
So they took a look at Saturn and found that its current inclination of 26.7 degrees could be the result of Rapid outward migration from its largest moonAnd Titan. They found that this can happen with almost no effect on the planet’s rotational speed.
This obviously raised questions about the most tilted planets in the solar system. Then 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 inches) 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.
Back to Uranus, the team ran simulations with a number of parameters, including the mass of the hypothetical moon. They found that a moon with a mass at least half the mass of Earth’s moon could tilt Uranus by about 90 degrees if it migrates more than 10 times the radius of Uranus at a speed greater than 6 centimeters per year.
However, in the simulations it was more likely to produce a larger moon similar in size to the tilt and rotation of Ganymede seen on Uranus today. However, the minimum mass – about half the Earth’s moon – is about four times the combined mass of the currently known moons of Uranus.
Businesses also take this into account. with an inclination of about 80 degrees, the moon It became unstable, causing a chaotic phase of its axis of rotation that ended when the Moon finally collided with the planet, “petrifying” the tilt and axial rotation of Uranus.
“This new image of the inclination of Uranus looks very promising to us”, write researchers.
“As far as we know, this is the first time that a single mechanism has been able to tilt Uranus and petrify its axis of rotation to its final state without causing a gigantic impact or other external phenomena. And some of the successful executions culminate in the localization of Uranus, which appears as a natural consequence of the dynamics, “Hmm To complete.
“This image also looks attractive as a general phenomenon: Jupiter is about to begin its tilt phase today, Saturn may be halfway there, and Uranus has completed its final phase, with its satellite destroyed.”
It is unclear whether Uranus hosted a moon large enough and with a sufficiently high migration rate to produce this scenario, and it would be difficult, the researchers say, to show it through observations.
However, a better understanding of the current migration rate of Uranus’ moons will go a long way towards solving these questions. If they were migrating at a high rate, it could mean that they formed from the debris of the ancient moon after it was destroyed eons ago.
Bring This is a Uranus probe.
The research was accepted Astronomy and astrophysics and available in arXiv.
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