Our galaxy has its own magneticfield and it is very different from the magnetic field of the Earth, since it is much weaker than it. Studying the magnetic field of our galaxy will help you learn more about star formation, cosmic rays and many other astrophysical processes. A group of astronomers from the University of Curtin in Australia and CSIRO (State Association of Scientific and Applied Research) are studying the magnetic field of the Milky Way. The result of their collaboration was the most comprehensive catalog of measurements of the magnetic field of the Milky Way in 3D. The study is published in the journal Monthly Notices of the Royal Astronomical Society.
What can the magnetic field map of the Milky Way tell about our galaxy?
The team worked with a LOFAR radio interferometer orLow-Frequency Array, developed by the Netherlands-based ASTRON Institute. LOFAR operates at radio frequencies below 250 MHz and consists of many antennas located in Europe. Researchers have compiled the largest catalog of magnetic field strength and direction to pulsars. In the course of their work, astronomers used pulsars to effectively probe the galaxy's magnetic field in 3D. The fact is that pulsars are distributed throughout the Milky Way, and intermediate material in the galaxy affects their radio wave radiation.
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As the pulsar radio waves pass throughgalaxy, due to the interference of free electrons, they are susceptible to an effect called dispersion. This means that high-frequency radio waves arrive earlier than low-frequency ones. Thanks to the data obtained, astronomers were able to measure the difference, called the "measure of dispersion" or DM. DM tells researchers the amount of free electrons between us and the pulsar. If DM is higher, it means that either the pulsar is farther away, or the interstellar medium is denser. Scientists then estimated the average magnetic field of the Milky Way in the direction of each pulsar in the catalog. The magnetic field of the galaxy affects all types of astrophysical processes. It forms the path that cosmic rays follow. Therefore, when astronomers study a distant source of cosmic rays, for example, an active galactic core, understanding the strength of the magnetic field can help them understand the object of study. The magnetic field of the galaxy also plays a role in the formation of stars. Although the effect is not fully understood, the strength of the magnetic field can affect molecular clouds.
The catalog is based on observations of 137 pulsars.in the northern hemisphere. However, at the moment the work cannot be called completed. In the future, it will be possible to supplement the map of the magnetic field of the Milky Way with the help of the largest radio telescope on Earth Square Kilometer Array (SKA), which is currently under development. SKA will be located both in Australia and in South Africa. Thanks to SKA, researchers will be able to get the highest resolution images. One of SKA’s long-term goals is to revolutionize our understanding of the galaxy, including creating a detailed map of the structure of the Milky Way and especially its magnetic field.