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Originally Posted by mickoking
Our Galaxies magnetic field is pretty weak (Earths=50 micro tesla, Milky Way=0.1 nano tesla) so I dont know if a compass would respond to it in intergalactic space? The galactic magnetic north is above the centre (core) of the Milky Way, probably somewhere in Opiuchus.
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Good point, the MW magnetic field is but a smidgeon of the Earth's.
The Earth's magnetic field is generated by our fluid iron core that creates a fairly coherent field, acting like a "giant bar magnet" as the textbooks put it. The magnetic north is easily defined as the north pole of the "bar magnet".
The Galaxy does not have a giant fluid iron core so does not act like a bar magnet with a north pole.
I believe that, relative to the Earth's, the MW magnetic field is fairly messy. The magnetic field lines are marked by sychrotronic radiation generated by pulsars, neutron stars and active black holes, of which there are numerous discrete and dispersed sources, creating magnetic force lines all over the shop. There is also the primordial magnetic field created when the galaxy formed. This has magnetic field lines running along the spiral arms. Your compass may be pointing somewhere along the magnetic field lines, but I wouldn't think it would be our version of the galactic north pole, or anywhere else in particular.
A good example of a messy magnetic situation is the Sun, which has its magnetic field twisted and distorted by the flows of plasma and magnetic storms (sunspots) on the surface. You wouldn't know where you compass would point next if you were on the surface of the Sun. Even here, the magnetic field would be more coherent than that which exists for the whole Milky Way Galaxy.
