[Martin Timothy]

This pic shows the relationships in the Milky Way family

The MW is surrounded by star clouds, which formed in emission nebulae at the tidal boundary of the galaxy, the gravity source can not keep the disc stable outwardly for ever, and bits will spin off and go their own way at that place, this is the physical force that makes all similar disc galaxies the same size give or take.

The arms in spiral galaxies are a density wave, down which Hole Matter travels from the center trailing expanding emission nebula in its wake, whence form globular clusters and stars, see file material and very rare photos.



Clusters of stars resembling bunches of grapes form, and as expansion continues the individual grapes become stars, see the Pleiades.



The Magellanic Clouds formed when a particularly virulent particles of Hole Matter arrived at the tidal boundary then spun off into intergalactic space, maybe to keep expanding to form other major spirals which will keep expanding from infinity - like a Mandelbrot Set - to spawn similar galaxies!