Anomalous rotation of Uranus was associated with a long-dead satellite

(ORDO NEWS) — Uranus rotates almost on its side, and the new model explains this by the influence of a large satellite, which eventually collapsed and fell into the planet. If the idea is correct, Jupiter and Saturn are going through a similar process today.

Uranus and Neptune are the most distant planets in the solar system. These are ice giants, which mainly consist of different types of ice: water, methane, ammonia. In addition, Uranus is distinguished by a unique feature of movement in space.

The axis of its rotation is inclined relative to the plane of the orbit very strongly, by almost 98 degrees. If the Earth and other planets can be compared to spinning tops, then Uranus is more of a rolling ball, which determines the unusual alternation of seasons on this distant giant.

The deviation of the axis of rotation of this planet is usually associated with a collision that it experienced in the early stages of formation.

However, new work by astronomers from France, Italy and the United States offers an alternative explanation for this phenomenon – the influence of a migrating satellite.

The article by Melaine Saillenfest and her colleagues has been accepted for publication in the journal Astronomy & Astrophysics and is available in the arXiv open preprint library.

Previously, Seilenfest et al. have already studied the influence of satellites on giant planets. In particular, their simulations predicted that due to the slow migration of the moons to more distant orbits, Jupiter’s axis of rotation in a few billion years will be tilted by 37 degrees, and not by three, as it is today.

Likewise, Saturn could have gotten its current tilt almost 27 degrees due to the gradual receding of Titan, the planet’s most massive moon. It is logical that scientists tried to apply this approach to Uranus, which is so distinguished by the tilt of its axis.

It is worth saying that the slow displacement of satellites into more distant orbits is a common and very common phenomenon. Tidal forces are constantly “sucking” energy from a rotating system of two bodies, leading to its gradual slowdown and an increase in orbit.

Even our own Moon is moving away from Earth by four centimeters a year. So such a scenario for Uranus with its dozens of satellites does not look exotic at all.

Calculations showed that a strong inclination of the ice giant’s orbit could be caused by a satellite with a mass about half that of the Moon if it moved more than ten radii of Uranus at a speed of more than six centimeters per year.

If the mass of the satellite was higher, then a more moderate migration is sufficient for the same effect. The only problem is that Uranus does not have such a satellite, and their total mass is several times less than half the mass of the Moon.

However, the new model also points to where the massive satellite could have disappeared, causing the deviation of the axis of Uranus.

She showed that when the deviation reached about 80 degrees, the satellite’s orbit could destabilize sharply, and eventually it fell into the planet. The satellite disappeared, and Uranus itself remained fixed in a new tilted position.

Such a picture is more logical than the impact of a massive body, and fits into what we observe around gas giants today.

“It looks like the same phenomenon,” write the authors of the work. “Jupiter is just starting to tilt, Saturn is already halfway there, and Uranus has completed the final stage of the process, which culminated in the destruction of the satellite (which caused the orbit to deviate.).”

Perhaps the observation of spacecraft, Chinese and American, which are preparing to visit Uranus in the early 2030s, will help put an end to this issue.

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