Uranus’ Magnetosphere Is Pretty Strange

Out of all the planets in our solar system, Uranus seems to get overlooked the most. Jupiter dwarfs it. Saturn’s rings run circles around those of Uranus. And unlike Mars, no one has considered setting up a summer home on Uranus. But it’s still a pretty incredible planet.

For one thing, the planet is on its side. Its axis of rotation is nearly level with its orbital path. For comparison, Earth’s axis tilts at about 23.5 degrees; Uranus’ axis has a tilt of 98 degrees. This means that Uranus practically rolls through its orbit (which is about 84 Earth-years long). Its polar regions receive prolonged exposure to the sun. In fact, Uranus’ poles get more sunshine than its equator does.

Why is Uranus’ orbit so wonky? Scientists suspect that millions of years ago, Uranus was involved in an enormous collision. Unfortunately, no one reported it to the Solar System Police, so we have no official record of it. But that might be why Uranus isn’t quite (up)right.
While we’ve known about Uranus’ peculiar tilt for a while, scientists at Georgia Tech have uncovered something new to us. Uranus’ magnetosphere powers on and off throughout a typical day. The researchers relied on data collected from Voyager 2’s 1986 flyby to simulate the ice giant’s magnetosphere.

A planet’s magnetosphere is the magnetic field the planet generates around itself. Not all planets have a prominent magnetosphere. Earth has a pretty hefty one, but the magnetosphere around Mars is much smaller relative to the planet’s size. One of the side benefits of a strong magnetosphere is that it acts like a force field and can repel some of the more harmful charged particles hurled out by the sun. Life on our planet wouldn’t be what it is today without the protection of Earth’s magnetosphere.

On the other hand, Uranus’ magnetosphere is like the planet — it’s wonky. It’s aligned about 60 degrees off from the planet’s axis. The combination of the magnetosphere alignment and Uranus’ rotation creates an odd situation in which the model predicted that the magnetosphere is effectively open for parts of Uranus’ day. That means charged particles from the solar wind can bombard the planet while the force field is down. But in other parts of the planet’s rotation, the magnetosphere is «on,» meaning it will deflect charged particles.

The scientists at Georgia Tech say that learning more about Uranus could help us understand many of the exoplanets we’ve discovered so far, many of which appear to be the size of ice giants like Uranus and Neptune. It could turn out that the peculiarities of Uranus are commonplace across planets in the Milky Way, meaning that, on the galactic scale, we could be the weirdos.


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