lilac, russet, fawn, dun, buff, grey, and other shades indistinguishable
by any name.

Our knowledge of binary star systems brings us to what may be regarded
as the threshold of the fabric of the heavens. For it is known that
other systems exist into the construction of which numerous stars enter.
These form intricate and complex stellar arrangements, in which the
component stars are physically united and retained in their orbits by
their mutual attraction.

CHAPTER VII

THE STARRY HEAVENS

TRIPLE, QUADRUPLE, AND MULTIPLE STARS.--These, when observed with the
naked eye, appear as single stars, but, when examined with a high
magnifying power, each lucid point can be resolved into several
component stars. They vary in number from three to half a dozen or more,
and form systems of a more complex character than what are observed in
the case of binary stars. In the usual construction of a triple system,
the secondary star of a binary is resolvable into two, each star being
in mutual revolution, whilst they both gravitate round their primary. By
another arrangement, a close pair control the movements of a distant
attendant.

One of the most interesting of triple stars is the tricoloured Gamma
Andromedae. The brilliant components of this system have their
counterparts in the topaz, the emerald, and the sapphire--the larger
star is of the third magnitude and of a golden yellow colour; the
secondary of the fifth magnitude and of an emerald green. These stars
are ten seconds apart, and, though they have been under observation
since 1777, no orbital movement has as yet been detected, but their
common proper motion indicates their close relationship and physical
connection. In 1842, Otto Struve discovered that the companion star is
itself double, and round it there gravitates a sapphire sun, which is
believed to accomplish a revolution of its orbit in about 500 years. If
round those suns there should be circling planetary systems of worlds
inhabited by intelligent beings, the varied effects produced by the
light emanating from those different coloured orbs would be of a very
beautiful and pleasing nature.

A system suggestive of the endless variety of stellar arrangement that
exists throughout the sidereal regions is apparent in the case of the
triple star Zeta Cancri. Two of the stars, of magnitudes six and seven,
form a binary in rapid revolution, the components of which complete a
circuit of their orbits in fift