Yerkes (or Morgan) Scheme
Created by American astronomer William Wilson Morgan. Together with Philip Keenan, Morgan 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.
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 |
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 |
Inclination | Explanation |
---|---|
1 | Galaxy is "Face-on" |
2 | |
3 | |
4 | |
5 | |
6 | |
7 | Galaxy is "Edge-on" |
So, for example, the Andromeda Galaxy is classified as kS5.
Read more about this topic: Galaxy Morphological Classification
Famous quotes containing the word scheme:
“We doubt not the destiny of our countrythat she is to accomplish great things for human nature, and be the mother of a nobler race than the world has yet known. But she has been so false to the scheme made out at her nativity, that it is now hard to say which way that destiny points.”
—Margaret Fuller (18101850)