Diagonal Defiance: New Mapping Reveals a Stunning "Magnetic Flip" in the Milky Way

University of Calgary researchers discover a massive diagonal magnetic flip in the Milky Way's Sagittarius Arm, revealing new secrets of galactic structure.

By: AXL Media

Published: Feb 25, 2026, 6:14 AM EST

Source: The information in this article was sourced from the University of Calgary

The Invisible Glue of the Galaxy While astronomers usually focus on the light from stars, Dr. Jo-Anne Brown and her team are charting the invisible force that prevents the Milky Way from collapsing under its own gravity. Magnetic fields act as a structural framework for galaxies, influencing star formation and the flow of cosmic rays. Understanding this field is essential for predicting how our galaxy will evolve over billions of years.

Mapping with Faraday Rotation Because magnetic fields are invisible, the team utilized a phenomenon called Faraday rotation. When radio waves from distant sources pass through regions of space filled with electrons and magnetic fields, the waves "twist" or rotate.

"You can think of it like refraction. A straw in a glass of water looks bent because of how light interacts with matter," explains PhD candidate Rebecca Booth.

By measuring these rotations across multiple radio frequencies at the Dominion Radio Astrophysical Observatory, the team created a high-fidelity dataset that acts as a "magnetic MRI" of the northern sky.

The Discovery of the Diagonal Flip The most shocking revelation came from the Sagittarius Arm, one of the Milky Way's primary spiral structures. While the majority of the galaxy’s magnetic field flows in a clockwise direction, the field in the Sagittarius Arm flows counterclockwise. Previous models assumed this transition was a vertical or abrupt boundary. However, the new data reveals that the reversal is actually diagonal.

3D Modeling of Galactic Magnetism Lead author Anna Ordog provided the data that first hinted at the diagonal shift, which Booth then used to construct a three-dimensional model. This model explains how the transition occurs deep within the galactic disk and how it would appear to observers on Earth. This "diagonal" orientation is a vital clue for physicists trying to understand the "dynamo" effect—the process by which a galaxy generates and maintains its magnetic field through the motion of plasma.