Uranus moves to the beat of his own strange little drum.
Although our Solar System shares many similarities with the other ice giant Neptune, it has a lot of its own quirks.
And it’s impossible to miss one of them: The axis of rotation is so crooked that it could be stretching out. That’s a massive 98 degrees inclination from the orbital plane.
And above all, it rotates clockwise – the opposite direction of most of the other planets in the Solar System.
A new study has found a plausible explanation for this strange behavior: A moon moving away from the planet causing Uranus to be pulled to its side. And it doesn’t even have to be a big moon. Something half the mass of our own Moon could do that, but a larger moon would be a more likely contender.
The reasoning was laid out in a paper led by astronomer Melaine Saillenfest of the National Center for Scientific Research in France. This article, which has not yet been peer-reviewed, has been accepted to the journal. Astronomy and Astrophysics and made available in preprint source arXiv.
Scientists have developed models to explain this strange behavior, such as a massive object colliding with Uranus. literally hit the sidesbut more preferred explanation and one Bundle of the smaller objects.
However, this hypothesis raises issues that are even more difficult to explain: namely, the frustrating similarities to Neptune.
The two planets have extremely similar masses, radii, rotational speeds, atmospheric dynamics and compositions, and strange magnetic fields. These similarities suggest that the two planets may have been born together, and reconciliation becomes much more difficult when you add planet-topping influences to the mix.
This has led scientists to look for other explanations, such as a wobble that might be elicited by a wobble. giant ring system or a giant moon Early in the history of the Solar System (albeit by a different mechanism).
But then, a few years ago, Saillenfest and his colleagues found something interesting about it. Jupiter. Thanks to its moons, the gas giant’s incline could increase from its current mild level of 3 percent. about 37 percent in a few billion yearsby the out-migration of its satellites.
Then they looked at Saturn and found that its current tilt of 26.7 degrees rapid emigration of the largest bear, Titanium. This could happen with almost no effect on the planet’s rotation rate.
Obviously, this raised questions about the most tilted planet in the Solar System. Therefore, the team performed simulations of a hypothetical Uranus system to determine if a similar mechanism could explain its properties.
It’s not unusual for moons to migrate. Our own Moon is currently moving away from Earth about 4 centimeters (1.6 inches) per year. Objects rotating around a reciprocal center of gravity exert a tidal force on each other, which causes their rotation to slow gradually. In turn, this loosens the grip of gravity, thereby widening the distance between the two objects.
Back on Uranus, the team ran simulations with a range of parameters, including the mass of the hypothetical moon. And they found that a moon with a minimum mass of half the Earth’s Moon could tilt Uranus 90 degrees if it migrated more than 6 centimeters per year, more than 10 times the radius of Uranus.
However, in simulations, a larger moon of comparable size to Ganymede was more likely to produce the tilt and spin we see on Uranus today. However, the minimum mass – about half the Earth’s Moon – is about four times the total mass of currently known satellites of Uranus.
Work corresponds to this. At an inclination of about 80 degrees, moon The moon eventually destabilized and “fossilized” the axial tilt and rotation of Uranus, triggering a chaotic phase for its spin axis that ended when it collided with the planet.
“This new picture of the tilt of Uranus looks very promising to us” write the researchers.
“To our knowledge, it is the first time that a single mechanism has been able to both tilt Uranus in its final state and fossilize its axis of rotation without resorting to a giant impact or other external phenomenon. The majority of our successful runs culminate where Uranus is located. ” Go on.
“This picture also looks appealing as a general phenomenon: Jupiter is about to begin its tilt phase today, Saturn could be midway and Uranus could complete the final phase with its moon destroyed.”
It’s not clear whether Uranus could host a satellite large enough and at a high enough migration rate to create this scenario, and it would be difficult to demonstrate this with observations, the researchers say.
However, a better understanding of the current rate of migration of the moons of Uranus would go a long way toward resolving these questions. If they are migrating at a high rate, it may mean that they formed from the debris of the old moon after it was destroyed a long time ago.
To bring o Uranus probe.
Research accepted Astronomy and Astrophysics available on and arXiv.
