Magnetic Fields in the Milky Way and in Galaxies (revised version of September 2023)

Understand

Most of the visible matter in the Universe is ionized, so that cosmic magnetic fields are quite easy to generate and due to the lack of magnetic monopoles hard to destroy.

• Magnetic fields have been measured in or around practically all celestial objects, either by in-situ measurements of spacecrafts or by the electromagnetic radiation of embedded cosmic rays, gas, or dust.
• The Earth, the Sun, solar planets, stars, pulsars, the Milky Way, nearby galaxies, distant radio galaxies, quasars, and even intergalactic space in clusters of galaxies have significant magnetic fields.
• Even larger volumes of the Universe may be permeated by so-far invisble magnetic fields.