Exploring galactic magnetism

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In astronomy, we try to understand the origin and evolution of the cosmos. We study how matter interacts with gravitational and electromagnetic fields. It is common knowledge that gravity plays a huge role in cosmic processes. For example, a gravitational field can be produced by objects that we can see such as stars, planets, moons, and galaxies. Indeed, it was the quest to understand gravitation and its role in the Universe that motivated much of Newton's classic works in physics. It is much less well known, however, that magnetic fields are also important in the evolution and structure of stars, galaxies, and other astrophysical systems. The fact that magnetic fields might be important in this way was only put forward in the 1940s. Magnetic fields are produced by electric currents, and unlike with gravity, we can "see" neither the currents nor the field. All we can do is look for subtle effects of both and try to infer what is happening. This is exacerbated by the fact that what we are looking at is invariably far away, and the signals we are working with are faint. Advancing our knowledge of cosmic magnetic fields is difficult.