New Radio Observations Reveal Intricate Magnetic Field Structures Within the Milky Way's Sagittarius Arm

Recent radio astronomy data gathered at the start of 2026 has provided an unprecedented look into the invisible magnetic framework of the Milky Way. These magnetic lines of force are essential components in the movement of interstellar gas and the birth of new stars, making their study vital for our grasp of galactic development. Dr. Jo-Anne Brown, a prominent researcher from the University of Calgary, notes that this magnetic field acts as a crucial structural support, preventing the Galaxy from collapsing under the immense weight of its own gravity.

This extensive research project, directed by Dr. Brown within the University of Calgary’s Department of Physics and Astronomy, culminated in the release of two significant scientific papers in January 2026. These findings were featured in "The Astrophysical Journal" and "The Astrophysical Journal Supplement Series." To achieve these results, the scientific team employed a multi-frequency strategy using the specialized radio telescope at the Dominion Radio Astrophysical Observatory (DRAO) located in British Columbia. Operated by the National Research Council of Canada, this facility scanned the northern skies across a frequency spectrum ranging from 350 to 1030 MHz, contributing vital data to the Global Magneto-Ionic Medium Survey (GMIMS).

To untangle the complex radio signals, astronomers utilized a phenomenon known as Faraday rotation. This effect, which was originally identified by Michael Faraday in 1845, describes how the polarization plane of radio waves rotates as they travel through ionized gas permeated by magnetic fields. By meticulously tracking these shifts, researchers can calculate the specific magnetic field component along the line of sight. This method serves as a sophisticated diagnostic tool, allowing scientists to map out the intricate magnetic architecture of our galaxy with high precision.

A major highlight of the study was the detailed examination of the Sagittarius Arm, one of the primary spiral structures within the Milky Way. Researchers identified a striking anomaly: the magnetic field within this specific arm is reversed relative to the broader galactic magnetic field. Dr. Brown explained that while the general field follows a clockwise orientation when viewed from a top-down perspective, the field within the Sagittarius Arm moves in a counter-clockwise direction. This discovery, made under the DRAO GMIMS of the Northern Sky (DRAGONS) project, represents the first time such a large-scale structural complexity has been documented.

Rebecca Booth, the lead author of the second study, introduced a cutting-edge three-dimensional model that interprets this magnetic inversion as a diagonal structure when observed from our vantage point on Earth. This research provides a fully calibrated and comprehensive dataset, marking a major milestone for Canadian contributions to the global astronomical community. Furthermore, the survey revealed that approximately 55% of the observed lines of sight exhibit Faraday complexity. This high percentage highlights a significant degree of heterogeneity within the galactic magnetic field, suggesting a much more turbulent environment than previously assumed.