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A huge magnetic tunnel surrounding the Solar System: the theory that explains one of the great mysteries of modern radio astronomy

Yes, in recent years we have learned that the Milky Way is not as flat as we thought, but generally speaking that does not change the substance: our galaxy is a gigantic flat disk of stars, dust, gas, planets and some dark matter with the unmistakable shape of a huge, fluffy pancake.

That’s clear. However, during the 1950s, radio astronomers began to detect something curious: there was a kind of arc that rose above (that is, to the “north” of the plane) of the galaxy. Not only that, that arc was emitting radio waves. They called it “Spur of the North Pole” and for decades it has been one of the great astronomical mysteries of recent years. Why did that structure exist? What was the point? How did it connect with the rest of the galaxy?


Over time, the researchers found a similar (though not identical) phenomenon in the “southern” region of the plane of the galaxy. Much has been theorized as to whether they were stretches of a pair of gas bubbles perpendicular to the center of the galaxy or something else. What had not occurred to anyone is that these two large magnetic structures were connected.

How do they connect?


However, that would explain a lot of things. Jennifer West, an astronomer at the University of Toronto in Canada, has been working for a few years on the idea that these two structures are interconnected by a system of what we could call magnetic filaments. These parallel filaments would surround the Orion Arm of the Milky Way, forming a kind of magnetic tunnel of more than 1,000 light years. Right in the center of that tunnel would be us and the rest of the Solar System that surrounds us.

Warped and twisted: the Milky Way was not as flat as we thought, but a consummate contortionist

Using up-to-date data, West and his colleagues have modeled these magnetic “scaffolds” that explain things like shape, polarization of electromagnetic radiation (i.e. how the wave twists) and the shine from the North Pole Spur and the southern region. There is still a long way to go to confirm the existence of the filaments and the tunnel, but, without a doubt, “it is incredible to imagine that these structures are everywhere, every time we look up at the night sky.”

Above all, because this model opens the doors to understand how magnetic fields are born and work at the galactic level. After all, “Magnetic fields don’t exist in isolation. They all have to connect to each other,” West explained. And this theoretical finding would allow to explain how local fields are connected with the larger-scale galactic magnetic field.

Image | Carlos Kenobi