Close encounters between galaxies, like that expected in 4 billion years with the Andromeda Galaxy rips off huge tails of gas, which, over time can coalesce to form dwarf galaxies in a ring at an arbitrary angle to the main disc.
The Milky Way is on a collision course with the most massive member of the group, called M31 or the Andromeda Galaxy.
Using a low-mass red dwarf as an average-mass star will give you a totally different answer for the total number of stars in our galaxy.