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amateurs, partly for their beauty and colour,
and partly as a test for telescopic defini-
tion. Among the many unexplained stel-
lar problems there is one noticed in double
stars that is thought by some to be likely to
throw light on stellar evolution. It is this:
There are many instances where one star of
the pair is comparatively faint, and the two
stars are contrasted in colour; and in every
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