Astronomers have a cataclysmic new theory to explain the tilt of Uranus

There are plenty of funny stuff About Uranus. Its seasons last as long as its days, it is the second-least-dense planet, and it has 27 moons.

But perhaps the most surprising fact about Uranus It is the only planet that has lines on its side—at least relative to the plane of its orbit.

The most common suggestion for why the planet is tilted 98 degrees on its axis is that it was hit by several large impacts early on. solar system structure.

However, new research from a team at the Sorbonne points to a possible alternative explanation — that Uranus had another, larger moon that pulled it on its side and then impacted the planet itself.

Model error

A flurry of research into the orbital mechanics of gas giants has been underway recently. That flurry helped point out a series of flaws in current models of what happened to Uranus. The most obvious flaw is highlighted by an analogy between Uranus and its neighbors – Neptune.

Neptune’s axial tilt is only 30 degrees (still a lot by planetary standards) but nowhere near the level of Uranus. However, both planets have similar rotation rates. Impacts large enough to push an entire planet onto its side will also have a significant effect on its spin rate.

So it is highly unlikely that a random minor effect would cause one planet to be about 70 degrees higher than the other while not affecting their rotation rates.

The similar spin rates indicate many “smooth” processes that took place over eons but dramatically affected the properties of the two gas giants.

The real reason for the tilt?

Scientists have already hypothesized a “great migration” of the outer planets through the inner Solar System and its primordial planetary cloud, which may have caused events such as the Late Heavy Bombardment, which is responsible for many of the craters visible to us. the moon

This made the researchers think – the axial tilt in gas giants is usually established during the years of its formation. The relatively small axial tilts of Jupiter, Saturn, and Neptune can be explained by one event each occurring after the planets were fully formed. However, the high tilt of Uranus is different.

Scientists think that this happened in two stages. First, a relatively large moon, about .03 percent the size of the planet, gets stuck in a resonant loop with its host planet and slowly pulls the planet along.

Due to the complex orbital mechanics, which is a nicely explained Recent paper According to the authors, published on the preprint server arXiv, a large enough moon could interact with the gravitational pull of its parent planet in a way that would pull it to its side.

However, the second stage is the more curious of the two, at least from an astronomical catastrophe perspective. Currently, Uranus has 27 known moons, none of which fit the description needed to produce such an orbital resonance. So, where did it go? Most likely, it crashed into the planet itself after an orbital anomaly destabilized its orbit.

There are still some problems with this two-phase theory – for example, will the current crop of Uranus’ moons survive a giant threading toward its ultimate destruction?

But based on the models the Sorbonne team ran, there seems to be a plausible physical scenario where Uranus ends up tilted with the correct orbit and rotation rate, and an impact on the planet destroys the satellite causing the tilt.

This is an intriguing concept that warrants further study. Unfortunately, it will probably take a long time to find any other physical evidence that could indicate the theory’s validity or not.

But at the very least, it’s an interesting thought exercise to imagine Uranus slowly being pulled by one of its moons over billions of years, only to eventually have that moon crash into it. Such a dramatic history would make the planet more interesting.

This article was originally published Universe Today By Andy Thomaswick. After this Original article here.