Morgan-Keenan Luminosity Class
Classification of stars is based primarily on their temperatures.
Luminosity classes
The Harvard scheme specifies only the surface temperature and some spectral features of the star. A more precise classification would also include the luminosity of the star.
luminosity class A classification scheme which groups stars according to the width of their spectral lines.
LUMINOSITY CLASS
If a star happens to be a red giant or a white dwarf, its distance determined by spectroscopic parallax will be incorrect.
Luminosity Classes
One problem facing early attempts at classifying stellar spectra was the fact that two spectra could have the same lines present, indicating that the stars had the same effective temperature, ...
Luminosity Class
A category of stars of similar luminosity; determined by the widths of lines in their spectra.
Lyman, Balmer and Paschen Series ...
Luminosity Class
(a) A measure of a star's intrinsic brightness, as determined from the star's spectrum.
luminosity class A classification scheme which groups stars according to the width of their spectral lines. For a group of stars with the same temperature, luminosity class differentiates between supergiants, giants, main-sequence stars and subdwarfs.
luminosity class - (n.)
One of several classes to which a star can be assigned on the basis of certain luminosity indicators in its spectrum. The classes range from I for supergiants to V for main-sequence stars (also known as dwarfs).
Luminosity Class: Stars are classified by luminous they are. The various luminosity classes correspond to regions on the HR diagram. The luminosity classes are I - Supergiants, II - Bright giant, III - Giant, IV - Subgiant, V - Main Sequence.
(a) Luminosity Class V stars, essentially defining the Main Sequence, that are currently supported by the fusion of hydrogen into helium in their cores.
The Yerkes Luminosity Classes: (by William Wilson Morgan and Philip Keenan)
TYPEStar
Ia
Very luminous supergiants ...
* In some cases the Luminosity class is not known, while in other cases, the spectral type is not known - that is why this column is incomplete.
Luminosity classes. As discussed on p. 12, there is a general correlation between arm structure and absolute magnitude for spirals, especially Sc systems.
More specifically, the term giant star refers to a star that belongs to the luminosity class III in the Yerkes spectral classification. Low-mass stars remain in this luminosity class until they settle down as white dwarfs.
what kind of star is it: what is its temperature, its luminosity class (dwarf star, giant star, supergiant, etc.)?
is it a single star, or a binary?
[8] The MK classification assigned each star a spectral type-based on the Harvard classification-and a luminosity class.
In the more modern system of spectral classification, called the MK system (after the American astronomers William W. Morgan and Philip C. Keenan who introduced it), luminosity class is assigned to the star along with the Draper spectral class.
The Roman numeral in the spectral class gives the luminosity class: I through V for supergiant, bright giant, giant, subgiant, and dwarf.
Another dimension that is included in the Morgan-Keenan-system is the luminosity class expressed by the Roman numbers I, II, III, IV and V, expressing the width of certain absorption lines in the star's spectrum.
For more information about stars including spectral and luminosity class codes, go to ChView's webpage on The Stars of the Milky Way.
Note: Thanks to Mike Stevens for point out that HD 10647 has also been designated q1 Eridani.
Spectral Types and Luminosity Class
for Some Bright Stars
Star Name Constellation Class Comments
Polaris ...
spectral class
The Columbia Encyclopedia, Sixth Edition
luminosity class
A Dictionary of Astronomy
Spectral Classes for Main Sequence Stars
The Columbia Encyclopedia, Sixth Edition ...
Stars may also be divided into luminosity classes based on their inherent brightnesses.
class
type ...
Imagine that you are an astronomer and you have detected a source that has a temperature of about 3700 Kelvin, and a luminosity of about 0.1. Examine the H-R diagram; explain what luminosity class and type of source this could be.
a plot of stellar absolute magnitude on BV color index, also showing surface temperature and radius; 30,600 stars within 120 parsecs (400 light years) of the sun are indicated by spectral type; farther stars are indicated by luminosity class.
 See also: Luminosity, Star, Dwarf, Mass, Light
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