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Mass–Luminosity Relation
As demonstrated by this plot, the luminosity of a star is a very strong function
of its mass. This "mass–luminosity relation" is determined by observations of
binary star systems used to obtain their masses and measurements of stellar
magnitudes combined with distance determinations to find the luminosities of
these stars.
Source: University of Oregon Introduction to Astrophysics, Mass–Luminosity Relation,
Image ID: ml.gif
Schematic Overview of the Hertzsprung–Russell Diagram
In the early 1900s, Ejnar Hertzsprung and Henry Norris Russell independently made the
discovery that the luminosity of a star is related to its surface temperature.
Hertzsprung and Russell both used the spectral class (which is related to the temperature)
in their plots. They ordered the stars as O, B, A, F, G, K, and M. Since the O
stars are the hottest, this means that in the H–R diagram, the temperature axis
is odd in that the temperature decreases as one moves to the right.
When luminosity versus temperature plots are made, stars do not fall randomly on the graph,
but instead are confined to specific regions, and evolve as they age through
the regions on this graph in particular patterns.
Source: University of Oregon Introduction to Astrophysics, H–R Diagram,
Image ID: hr.xbm
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Mass–Luminosity Relation
Schematic Overview of the Hertzsprung–Russell Diagram