stylistic:tone, information:extraction
Magnetic fields

Galaxies have magnetic fields of their own. A galaxy's magnetic field influences its dynamics in multiple ways, including affecting the formation of spiral arms and transporting angular momentum in gas clouds. The latter effect is particularly important, as it is a necessary factor for the gravitational collapse of those clouds, and thus for star formation.

The typical average equipartition strength for spiral galaxies is about 10 μG (microgauss) or 1 nT (nanotesla). By comparison, the Earth's magnetic field has an average strength of about 0.3 G (Gauss) or 30 μT (microtesla). Radio-faint galaxies like M 31 and M33, the Milky Way 's neighbors, have weaker fields (about 5 μG), while gas-rich galaxies with high star-formation rates, like M 51, M 83 and NGC 6946, have 15 μG on average. In prominent spiral arms, the field strength can be up to 25 μG, in regions where cold gas and dust are also concentrated. The strongest total equipartition fields (50–100 μG) were found in starburst galaxies —for example, in M 82 and the Antennae; and in nuclear starburst regions, such as the centers of NGC 1097 and other barred galaxies.