The scintillation or twinkling of the stars is accompanied by
variations of colour, which have been remarked from a very early age.
M. Arago states, upon the authority of M. Babinet, that the name of
Barakesch, given by the Arabians to Sirius, signifies _the star of
a thousand colours_; and Tycho Brahe, Kepler, and others, attest to
similar change of colour in twinkling. Even soon after the invention
of the telescope, Simon Marius remarked that by removing the eye-piece
of the telescope the images of the stars exhibited rapid fluctuations
of brightness and colour. In 1814 Nicholson applied to the telescope a
smart vibration, which caused the image of the star to be transformed
into a curved line of light returning into itself, and diversified by
several colours; each colour occupied about a third of the whole length
of the curve, and by applying ten vibrations in a second, the light of
Sirius in that time passed through thirty changes of colour. Hence the
stars in general shine only by a portion of their light, the effect of
twinkling being to diminish their brightness. This phenomenon M. Arago
explains by the principle of the interference of light.
Ptolemy is said to have noted Sirius as a _red_ star, though it is now
white. Sirius twinkles with red and blue light, and Ptolemy’s eyes,
like those of several other persons, may have been more sensitive to
the _red_ than to the _blue_ rays.--_Sir David Brewster’s More Worlds
than One_, p. 235.
Some of the double stars are of very different and dissimilar colours;
and to the revolving planetary bodies which apparently circulate around
them, a day lightened by a red light is succeeded by, not a night, but
a day equally brilliant, though illuminated only by a green light.