Scientists explain why Uranus rotates on its side

Астрономы объяснили, почему Уран вращается на боку

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American astronomers have put forward a new hypothesis that explains the unusual inclination of the rotation axis of the planet Uranus. This is described in the Astrophysical journal.

Most Solar system planets have their poles are more or less oriented in one direction. And most of them rotate counterclockwise when viewed from above. Uranium orientation in space is different from the other planets, its axis of rotation lies as if on the side relative to the plane of rotation of this planet around the Sun and rotates it clockwise.

Usually for the explanation of this oddity is the hypothesis that once upon a time there was a clash of Uranium with a large cosmic body that knocked the planet. Although this scenario is not impossible, in this model, there are several significant contradictions, for example, it cannot explain why none of the moons of Uranus does not have the same inclined orbit. Furthermore, the ice moon, and a powerful blow enough to turn the axis of rotation of the planet, was to generate enough heat to evaporate the ice on these moons, making them rocky.

Astronomers from the University of Maryland Ziv Rogosinski (Zeeve Rogoszinski) and Douglas Hamilton (Douglas Hamilton) invented a new script which removes these contradictions. According to their hypothesis, the Uranium could be tilted to the side of the giant ring system.

Now, the rings of Uranus are very weak, consisting of the smallest particles of dust, but scientists believe that 4.5 billion years ago, at the time of formation of the Solar system they could be much more massive. That ring can be temporary and short-lived, according to the data obtained with the automatic interplanetary station “kassini” studying Saturn’s rings.

Model Rogachevskogo and Hamilton suggests that a large ring system rocked the Uranium, causing it to rotate around its axis with a noticeable spin precession — type as starts to wobble of the rotating spinner. Then, if the precession of the planet rotation axis got in resonance with the orbital precession of the planet (the so-called slow rotational shift of the ellipse of the orbit relative to the Sun), the planet could deploy.

Resonance between spin and orbital precession is known as the spin-orbit resonance, and it can generate a large axial tilt. It is believed that the resonance of this type has led to the axial tilt of Saturn compared to the direction of the axis of its closest sibling, Jupiter.

Earlier to explain the axial tilt of Uranus have put forward the hypothesis of spin-orbit resonance, but as a body, resonated, it was proposed a hypothetical Ninth planet.

The authors believe that the ring system that is part of the process of formation of giant planets, suitable for it. They modeled Uranus and Neptune with larger discs to see how they interact with the planets, and discovered that the ring system for a million years may reject the axis of rotation of the planet at 70 degrees. This model easily explains the axial tilt of Neptune, which represents 30 degrees. But for Uranium, obviously, there was some additional impact, and the theory of a collision with another cosmic body still has the right to life. But in this context, it can be a small asteroid and not a larger cosmic body, which makes the scenario more likely.

“Although we can generate slopes greater than 70 degrees only in rare cases and are not able to manage slopes above 90 degrees, the subsequent collision with the object, constituting about half of the mass of the Earth may tilt the Uranium from 70 to 98 degrees — the researchers write in their paper. — Minimizing weight and number of giant drummers from two or more one increases the likelihood of creation of spin States of Uranium by about an order”.

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