The name is absent

The Sizes and Masses of the Stars 83
come available. Recent work by Jackson at Greenwich
shows that the average mass of a pair of dwarf stars is
very close to twice that of the Sun, so that the individual
components are strictly comparable with the Sun in mass.
There is evidence, however, that the average mass differs
for the various spectral classes. Ludendorff showed, a
decade or more ago, from the data regarding spectroscopic
binary systems, that the average mass of a pair of B-stars
was about three times that of those of Class A and more
than ten times that of the Sun. This conclusion was con-
firmed and extended by some work of mine a little later.
Seares, who has recently gone over the same ground with
more extensive data, confirmed these results and finds that
the mean mass of a pair of stars of Class BO is eighteen
times that of the Sun, 10 for AO, 4.4 for F0, and 1.7 for
GO, then diminishing slowly to 1.4 for M. For classes B
and A these values apply to the giants and dwarfs together,
for the later classes to the dwarf stars. For the redder
giants the average mass of a pair is about 9 times the
Sun’s, according to a determination of mine, which I hope
to revise in a year or two, but which is probably fairly
reliable. These mean masses show that the stars are far
more similar to one another in mass than in any other
characteristic. This conclusion is confirmed by the individ-
ual values. If we confine ourselves to cases in which the
errors of observation are not so large as to vitiate the
results, we find no case of a mass exceeding twenty times
that of the Sun, and none less than one-seventh of the
Sun’s. There appears to be a definite correlation between
mass and brightness. The large masses all belong to B-stars
of great luminosity—the smallest one to a tiny M-star,
about 1/3000 as bright as the Sun. The average values for
the giant and dwarf stars point in the same direction.

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