Galaxy Morphology and Classification

Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance, shape, structure, and distribution of light. There are several schemes in use by which galaxies can be classified according to their morphologies, the most famous being the Hubble sequence, devised by Edwin Hubble and later expanded by Gérard de Vaucouleurs and Allan Sandage. However, galaxy classification and morphology are now largely done using computational methods and physical morphology. The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1926.

Figures (10)

Tuning-fork-style diagram of the Hubble sequence

Spiral galaxy UGC 12591 is classified as an S0/Sa galaxy.[1]

The Hubble sequence throughout the universe's history[8]

Hubble – de Vaucouleurs Galaxy Morphology Diagram

NGC 6782: a spiral galaxy (type SB(r)0/a) with three rings of different radii, as well as a bar

NGC 7793: a spiral galaxy of type SA(s)d

The Large Magellanic Cloud: a type SBm galaxy

The galaxy located in the image is 4C 73.08, a giant elliptical galaxy.[15]

Key Points

For example, a weakly barred spiral galaxy with loosely wound arms and a ring is denoted SAB(r)c.
An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image.
A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars.

Terms

Tap a term for a plain-language explanation.

Sources & licensing(4)

Wikipedia contributors — en.wikipedia.org/wiki/Galaxy_morphological_classification (Creative Commons Attribution-ShareAlike 4.0)
Wikipedia contributors — en.wikipedia.org/wiki/Hubble_sequence (Creative Commons Attribution-ShareAlike 4.0)
Wikipedia contributors — en.wikipedia.org/wiki/Barred_spiral_galaxy (Creative Commons Attribution-ShareAlike 4.0)
Wikipedia contributors — en.wikipedia.org/wiki/Elliptical_galaxy (Creative Commons Attribution-ShareAlike 4.0)