Why should a galaxy have bluish spiral arms dotted with red patches and dark lanes.  Why should it have a central region that is yellow and spherical rather than flat? Why are they flat to begin with? Because Galaxies are so huge, and made from hundreds of Billions of stars that change over the course of their lives, a galaxy shows the entire life cycle of a star in its own structure. Stars are born along spiral arms, where most of the thick dust and gas clouds are concentrated.  The dark dust lanes of spiral arms condense to form stars,...