Spiral galaxies are unique. Our Milky Way is spiral, and it has sprawling magnetic fields. As to how these magnetic fields are formed, scientists have several theories, but the process is still not clearly understood.
A team of international researchers has attempted to find answers and analyzed the magnetic field of NGC 4217, a galaxy that's quite similar to our own Milky Way. They ended up discovering never-before-seen magnetic field structures, and according to data they've gathered, star formation and star explosions, so-called supernovae, are responsible for the visible structures.
The team led by Dr. Yelena Stein from Ruhr-Universität Bochum, the Centre de Données astronomiques de Strasbourg and the Max Planck Institute for Radio Astronomy in Bonn together with US-American and Canadian colleagues, published their report in the journal Astronomy and Astrophysics, released online on 21 July 2020.
NGC 4217 is approximately 67 million light-years away from the Milky Way, which in space distance is relatively close. The researchers hope to successfully transfer some of their findings to our home galaxy.
Data from NGC 4217 revealed new remarkable structures. The galaxy has a unique X-shaped magnetic field, which extends far outwards from its disk at 20,000 light-years away.
Apart from the X-shaped magnetic field, researchers also discovered two large bubble structures and a helix structure. These large bubble structures, also called superbubbles, come from places where many huge stars explode as supernovae but also where stars are formed that emit stellar winds in the process. According to the team, there may be a connection between these occurrences.
Another never-before-seen structure is the large loop structures in the magnetic fields along with the entire galaxy. Stein believes that these structures are triggered by star formation.
The team used a combination of different strategies that allowed them to visualize the chaotic and ordered magnetic fields of NGC 4217 both along the line of sight and perpendicular to it. A detailed image of the structures was found.
Stein and her team optimized the results by combining the data evaluated by way of radio astronomy with an image of the galaxy that was captured in the visible light range.
According to Stein, data visualization is especially important. "Because when you think about galaxies, magnetic fields are not the first thing that comes to mind, although they can be gigantic and display unique structures," she pointed out. "The image is supposed to shift the magnetic fields more into focus."
