Name: Matt L Rasmussen
What is the formula for mass-luminosity relation?
The various sources I have looked at do not give an equation as such; they
merely state that if you graph Log(L) versus Log(M) for a number of stars on
the main sequence, they tend to lie in a fairly thin band. But as the
Encyclopedia of Physical Science and Technology points out, during the
course of a star's lifetime its luminosity varies considerably, whereas its
mass remains nearly constant; so it is clear that no single equation will
work for all stars at all stages of stellar evolution. The above-mentioned
source says that L increases approximately as M^3 for stars on the order of
10 solar masses, as M^4.5 for stars of around 1 solar mass, and as M^2 for
low-mass stars. Further, this is only good for stars that have "just"
entered the main sequence.
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Update: June 2012