Quote from: Dave Lev
72 present of the galaxies that we observe are spiralYou seem to imply that these are flat galaxies that don't show a spiral structure.
That's because there are many other types of galaxies that aren't flat:
- Elliptical galaxies are formed by the collision of two or more galaxies, which disrupts any spiral pattern, and consumes most of the dust (so new arms can't form). This will happen to Milky Way + Andromeda = "Milkomeda"
- Dwarf galaxies/irregular galaxies/globular clusters : Their arms have been distorted and ripped off by interactions with a larger galaxy, leaving no record of spiral arms (if any)
Total Speculation: We now know that most galaxies have a central black hole.
- We know that there are relativistic jets produced from the accretion disk around this black hole
- Sometimes there are 2 or more central black holes, remnants of previous galactic mergers
- We expect that the axis of the central jets will change when central black holes merge (and there are examples of this in radiotelescope images)
- So what if a black hole merger produces a jet whose axis intersects the disk of the galaxy?
- Won't that set off linear changes in the disk (eg a barred spiral)?
Of course, a relativistic jet might not be comfortable for life in the spotlight...