Spiral galaxies may be excellent visual objects through large scopes but there are Manny different forms of spiral galaxy. Spiral galaxies are further classified into several subtypes based on their specific features:
- Normal Spirals (S)
These galaxies have spiral arms that emanate directly from the nucleus. They are subclassified as Sa, Sb, and Sc based on:- Tightness of the spiral arms (Sa being the tightest, Sc the most open)
- Size of the nucleus (Sa having the largest, Sc the smallest)
- Smoothness of the arms (Sa being smoother, Sc more clumpy
The top image of M31 The Andromeda Galaxy (M31) is classified as a Spiral galaxy SAb. M31 is a visible object by the naked eye! The lower image of M64 also known as the Black Eye Galaxy, is a spiral galaxy of type Sb. It’s located in the constellation Coma Berenices
- Barred Spirals (SB)
These galaxies have a prominent bar-like structure through the nucleus, with spiral arms emerging from the ends of the bar. They are subclassified as SBa, SBb, and SBc, following similar criteria as normal spirals. - Intermediate Spirals (SAB)
Some galaxies show characteristics between normal and barred spirals, classified as SAB. - Lenticular Galaxies (S0)
These are transitional types between elliptical and spiral galaxies. They have a disc and bulge but lack visible spiral arms.
Additional classifications include:
Grand Design Spirals: Galaxies with prominent, well-defined spiral arms
Flocculent Spirals: Galaxies with patchy, less distinct spiral arms
The classification of spiral galaxies can be challenging, as their appearance varies depending on their orientation relative to Earth. Face-on spirals show their bulge and spiral arms clearly, while edge-on spirals are more difficult to identify