Understanding the magnetic field of the Milky Way is crucial for comprehending the galaxy's structure and evolution. According to Professor Brown from the University of Calgary, "Without a magnetic field, the galaxy would collapse in on itself due to gravity." This insight emphasizes the need for accurate models to predict the magnetic field's future.
New Insights into the Milky Way's Magnetic Field
Recently, Brown and her team published two significant studies in The Astrophysical Journal and its Supplement Series. These works present a comprehensive dataset available for astronomers globally, coupled with a novel model that enhances our understanding of the Milky Way's magnetic field development.
The research utilized a state-of-the-art radio telescope at the Dominion Radio Astrophysical Observatory in British Columbia, a facility of the National Research Council Canada. This advanced instrument enabled the team to scan the northern sky across various radio frequencies, yielding intricate details about the galaxy's magnetic field structure. Dr. Anna Ordog, the lead author of the first study, noted, "The broad coverage really lets you get at the details about the magnetic field structure."
The result is a high-quality dataset generated as part of the Global Magneto-Ionic Medium Survey (GMIMS), an international initiative aimed at mapping the Milky Way's magnetic field.
Understanding Faraday Rotation
The researchers employed a technique known as Faraday rotation to trace the magnetic field. This phenomenon occurs when radio waves traverse regions filled with electrons and magnetic fields, leading to a shift in the waves. PhD candidate Rebecca Booth explained, "You can think of it like refraction. A straw in a glass of water looks bent because of how light interacts with matter. Faraday rotation is a similar concept, but it's electrons and magnetic fields in space interacting with radio waves."
By meticulously analyzing these subtle variations in radio signals, the team successfully mapped the arrangement of the magnetic field across extensive areas of the galaxy.
A Unique Magnetic Reversal in the Sagittarius Arm
Booth's second study spotlighted an intriguing feature within the Milky Way: the Sagittarius Arm, where the magnetic field runs counter to the rest of the galaxy. "If you could look at the galaxy from above, the overall magnetic field is going clockwise," Brown explained. "However, in the Sagittarius Arm, it's going counterclockwise. We previously struggled to understand how this transition occurred until Anna presented some data that revealed the reversal's diagonal orientation."
Building upon Ordog's findings, Booth developed a three-dimensional model elucidating this magnetic reversal. "My work presents a new three-dimensional model for the magnetic field reversal. From Earth, this would appear as the diagonal that we observe in the data," Booth clarified.
