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VIDEO – A numerical simulation reinforces the hypothesis that the highly inclined axis of rotation of the gas planet is the result of a cataclysmic collision with a very large impactor very early in the history of the Solar System. [19659002UranusisastrangeexceptionintheSolarSystemWhereasthesevenotherplanets(MercuryVenusEarthMarsJupiterSaturnandNeptune)areonlyslightlyinclinedthisonehastheparticularityofbeingcompletelyrecumbentItsaxisofrotationthusformsanangleof98°withtheplaneoftheeclipticinwhichtheplanetsorbitHowtoexplainthissituation?IftherearesomealternativescenarioslikethatofagiantmoonthatwouldhavegraduallytiltedtheplanetbeforebeingejectedduringarapprochementwithSaturnthevastmajorityofastronomersagreedthatagiantimpactorwouldberesponsibleforthisshift
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An American-British team, led by Jacob Kegerreis of Durham University, supports today this hypothesis using numerical simulations of a very fine resolution whose results are published in the journal The Astrophysical Journal. . "We studied more than 50 impact scenarios to see if we could recreate the conditions that explain the evolution of the planet," the researcher said in a statement. "Our results show that the most likely would be that Uranus had suffered a cataclysmic collision in his youth with an object twice as mbadive as the Earth, if not more, hitting her on the side and triggering the events that made it possible to shape the planet as we see it today. "
Their simulation confirms that such an impact, which would have occurred more than 4 billion years ago, would not have gotten rid of the planet of its atmosphere. On the other hand, part of the Uranus moons and its rings could have formed from debris, in the equatorial plane of the planet, where they are still today. The pre-existing moons could also have been destabilized by the impact to join these orbits, according to their calculations.
But that's not all. Other mysteries surround Uranus. Unlike other gaseous giants, Uranus does not emit more heat than it receives from the Sun. "One would expect in principle that the considerable heat stored at the time of their formation continues to dissipate today," says Tristan Guillot, specialist in the formation of gas giants at the Observatory of the Côte d'Azur. "Densely deep layers of material could interfere with the outward flow of heat, but it is not known exactly how deep." Modeling also fails to establish it, but researchers say that material from the dislocation of the impactor could be at the origin.
Missions to Uranus?
The impactor could finally have created "lumps" inside the gaseous planet, which would allow to explain the magnetic field tilted and off-center of the planet, whose researchers today struggle to explain the curious geometry.
If this new simulation solves elegantly (at least qualitatively) all these mysteries, all this is still based on a very limited number of observations. For example, the Voyager 2 spacecraft has flown over the planet, quickly and at a good distance. It was in 1986. No dedicated space mission was ever sent to Uranus. "Missions to Neptune and Uranus are under discussion, both at NASA and at the European Space Agency," says Tristan Guillot. "The projects are still embryonic, but I think the community is ripe. The trip is long, four times more than to travel to Jupiter, but I hope that in 20 or 30 years, we will have data to better understand these planets. They could tell us a lot about the history of the Solar System as a whole. "
