Editing Galaxy morphological classification (section)

== Yerkes (or Morgan) scheme ==
The Yerkes scheme was created by American astronomer [[William Wilson Morgan]].  Together with [[Philip Childs Keenan|Philip Keenan]], Morgan also developed the MK system for the classification of stars through their spectra. The Yerkes scheme uses the spectra of stars in the galaxy; the shape, real and apparent; and the degree of the central concentration to classify galaxies.<ref>{{Cite web|url=https://ned.ipac.caltech.edu/level5/CLASSIFICATION/yc.html|title=The Yerkes Classification|website=ned.ipac.caltech.edu|access-date=2019-02-06}}</ref>

{| class="wikitable"
!Spectral Type
!Explanation
|-
| a || Prominent A stars
|-
| af || Prominent A–F stars
|-
| f || Prominent F stars
|-
| fg || Prominent F–G stars
|-
| g || Prominent G stars
|-
| gk || Prominent G–K stars
|-
| k || Prominent K stars
|}

{| class="wikitable"
!Galactic Shape
!Explanation
|-
| B || Barred spiral
|-
| D || Rotational symmetry without pronounced spiral or elliptical structure
|-
| E || Elliptical
|-
| Ep || Elliptical with dust absorption
|-
| I || Irregular
|-
| L || Low surface brightness
|-
| N || Small bright nucleus
|-
| S || Spiral
|}

{| class="wikitable"
! Inclination !! Explanation
|-
| 1 || Galaxy is "face-on"
|-
| 2 || 
|-
| 3 || 
|-
| 4 || 
|-
| 5 || 
|-
| 6 || 
|-
| 7 || Galaxy is "edge-on"
|}

Thus, for example, the [[Andromeda Galaxy]] is classified as kS5.<ref>{{Cite web|url=http://www.daviddarling.info/encyclopedia/G/galaxy_classification.html|title=galaxy classification|last=Darling|first=David|website=www.daviddarling.info|access-date=2019-02-06}}</ref>