When I did my yearlong Mission to the Solar System series back in 2015, the planet Neptune stood out as having the weirdest and wackiest magnetic field. Here’s a totally legit photograph from 1989 taken by the Voyager 2 space probe. As you can see, Neptune is really confused about how magnetic fields are supposed to work.
But since 2015, science has learned more about the other three gas giants in our Solar System. Neptune’s magnetic field is still really weird, but it’s no longer clear that it is the definitive weirdest.
- Jupiter: Based on data from the Juno mission, it looks like Jupiter has three poles instead of two. There’s a north pole, right about where you’d expect it to be. Then the magnetic field lines emanating from the north pole connect to two separate south poles. The first south pole is about where you’d expect a south pole to be. The other one is near the equator. Click here for more about Jupiter’s “non-dipolar” magnetic field.
- Saturn: As Sherlock Holmes says in one of his many adventures, “Depend upon it, there is nothing so unnatural as the commonplace.” According to data collected during the Cassini mission’s Grand Finale, Saturn’s magnetic field is almost perfectly aligned with its rotation. At first blush, that might seem quite normal. Commonplace, even. Except no other planet’s magnetic field is so perfectly aligned. Not even close. Apparently planetary scientists didn’t think such a thing was even possible. Click here for more about the “negligible tilt” of Saturn’s magnetic field.
- Uranus: The planet Uranus is tipped over sideways, and its magnetic field is tipped over further still. According to recent computer simulations, these two factors combine to cause Uranus’s magnetic field to tumble over itself “like a child cartwheeling down a hill,” as one researcher put it. This leads to a “periodic open-close-open-close scenario” where the solar wind can flow in toward the planet then suddenly be blocked, then suddenly flow in again, and then suddenly be blocked. If these simulations are correct, the Uranian aurora may flick on and off like a light switch. Click here for more about the “topsy-turvy motion” of Uranus’s magnetic field.
- Neptune: In 1989, Voyager 2 discovered that Neptune’s magnetic field is lopsided. The magnetic field doesn’t run through the planet’s core. Instead it runs through a seemingly random point about halfway between the core and the “surface” (by which I mean the topmost layer of the atmosphere). Also, only one of the poles ends up being near the planet’s “surface.” The other pole is buried somewhere deep in the planet’s interior. For more about Neptune’s “badly behaved” magnetic field, click here.
If I had to choose, I’d probably still give Neptune the award for weirdest magnetic field. But the competition is a lot tighter than it used to be. Maybe the real lesson here is that gas giants in general have wild and crazy magnetic fields.
So if you had to pick, based on all this new info, which planet do you think deserves the award for the weirdest magnetic field?
P.S.: Also, the Cassini mission discovered there’s an electric current flowing between Saturn and its innermost ring.