Type SB galaxy

Barreled spiral galaxies, in which the spiral arms arise from a straight "bar" passing through the center, are referred to as type SB. They usually contain a central bulge, often sharing many properties with elliptical galaxies, surrounded by a thin rotating disk containing whatever spiral structure there may be. Spirals are subdivided into a sequence jointly defined by the winding and prominence of the spiral arms, and the relative importance of the central bulge. SBa galaxies have a bright bulge and tightly wound arms, while SBc galaxies have loosely wound arms and a relatively less important bulge. As more detail was observed in some galaxies, intermediate substeps (Sab,Sbc,Scd,S0/a) were added when necessary.