Astrophysics (Index)About

galaxy classification

(Hubble sequence, Hubble classification)
(morphological classification of galaxies)

The commonly-used galaxy classification indicates a galaxy's morphology (galaxy morphology), i.e., shape and overall structure. Edwin Hubble developed the basic classification still used, the Hubble types, known collectively as the Hubble sequence or Hubble classification (though current usage includes refinements subsequent to Hubble's work, e.g., by Allan Sandage and Gérard de Vaucouleurs):

(The term disk galaxy for a disk-like shape includes the above spiral and lenticular galaxies.) Hubble laid out the types in a Y-like diagram in the shape of a horizontal tuning fork and you do see references to the classification-structure as a tuning fork. More recent developments, generally indicated by a suffix or prefix, add more detail, often distinguishing galaxies formerly classified as "irregular". For example, the classification "SBm", i.e., the m suffix) is based upon the Large Magellanic Cloud's form, which does have characteristics associated with the classic barred spiral. In the less-developed system, the LMC falls under "irregular".

Further reading:

Referenced by pages:
elliptical galaxy
lenticular galaxy (S0)
Large Magellanic Cloud (LMC)
Morgan classification
N galaxy
NGC 1600
Spindle Galaxy (NGC 5866)
NGC 6946
PCA analysis
peculiar galaxy (p)
Small Magellanic Cloud (SMC)
spiral galaxy
3C 295
3C 48
Ursa Major II Dwarf
van den Bergh galaxy classification