The Hubble sequence is a morphological classification scheme for galaxies published by Edwin Hubble in 1926. It is often colloquially known as the Hubble tuning-fork diagram because the shape in which it is traditionally represented resembles a tuning fork.
It was invented by John Henry Reynolds and Sir James Jeans.
The giant elliptical galaxy ESO 325-G004.
The Spindle Galaxy (NGC 5866), a lenticular galaxy with a prominent dust lane in the constellation of Draco.
The Pinwheel Galaxy (Messier 101/NGC 5457): a spiral galaxy classified as type Scd on the Hubble sequence
The barred spiral galaxy NGC 1300: a type SBbc
Galaxy morphological classification
Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance. 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 GĂ©rard de Vaucouleurs and Allan Sandage. However, galaxy classification and morphology are now largely done using computational methods and physical morphology.
Spiral galaxy UGC 12591 is classified as an S0/Sa galaxy.
The Hubble sequence throughout the universe's history
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.