galaxies, classification

galaxies, classification

Galaxies may be classified according to a variety of criteria, including morphology (shape, concentration, and structure), spectroscopy (integrated spectrum, etc.) colorimetry (integrated color, etc.), photometry (luminosity, etc.), and unusual activity at various wavelengths (radio, infrared, X-ray, etc.). The Hubble classification is based on morphology whereas Morgan's classification is basically a quantitative spectroscopic classification.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006