Why most of the galaxies are having two spiral arms only?

[jayaramas]

why most of the galaxies are having two spiral arms only?

 

[mathman]

Do they?

http://en.wikipedia.org/wiki/Spiral_galaxy

The general description seems to imply many arms.

 

[phinds]

why most of the galaxies are having two spiral arms only?

Yes, I agree w/ mathman. What gave you the idea that 2 arms was the norm? Can you give a reference?

 

[kcajrenreb]

I have never heard of a galaxy with only two arms, although if there was such a thing, that would be interesting to see.

 

[phinds]

I have never heard of a galaxy with only two arms, although if there was such a thing, that would be interesting to see.

I may be wrong, but I DO seem to remember once (and only once) seeing a pic of a galaxy with only two arms ... or it might be that it only SEEMED to have just two arms because the two were so much stronger than the others ... I can't really recall.

 

[mathman]

Barred spirals may have only two arms, each coming off an end of the bar.