The Caldwell Objects

play begins at 8:00 p.m., when my eyes knock on
the door of the northwestern horizon. If the night
is clear, the door opens. And there, standing with
perfect posture, is the matronly form of the
Northern Cross. Dressed in the evening gown of
the Milky Way, she welcomes me with open
arms: "Why, Stephen, what a pleasant surprise!
Come and join us!" Orion and his dogs suddenly
burst through the back door of the southeastern
horizon; winds lap at me like wet tongues,
sending shivers up and down my spine. I look to
the north and see three more friends, Cepheus,
Cassiopeia, and Perseus, parading over the
snowcapped hill of the celestial pole. My
attention is drawn to Perseus because he carries a
special gift wrapped in mist. The moment has
come. I use my telescope, and the magic of
magnification, to open the gift. The mist
evaporates to reveal two crystal spheres. I look
away from the telescope and see Perseus hanging
them at the apex of the heavens. "If enough
people wish for snow on Christmas day," he tells
me, "their thoughts will shatter the crystal and
the pieces will fall and turn to snow" As you can
imagine, if snow did fall the next day I could see
in it pieces of this shattered crystal glinting
sharply in the morning light.
It's not surprising that the Double Cluster
could ignite a fire of imagination in a young
skywatcher. Around the globe the great Double
Cluster in Perseus is hailed as one of the most
impressive telescopic sights in the heavens.
Under dark skies the glow from this pair of
stellar islands stretches across two Moon diameters
and looks like a 4th-magnitude knot in the
ruffled folds of the Milky Way, about halfway
between Delta (δ) Cassiopeiae and Gamma (γ)
Persei.
Although Herschel is credited with discovering
these objects' star-cluster nature, the
combined glow of NGC 869 and NGC 884 has
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been known since antiquity. Hipparchus recorded
them as a "cloudy spot." In his book Star
Names: Their Lore and Meaning, Richard Hinckley
Allen says that Ptolemy noted them as a "dense
mass," and subsequent pretelescopic astronomers
saw them as nebulous entities. Allen also says
that the twin clusters "seem strangely to have
escaped the notice of astrologers, who, as a rule,
devoted much attention to clusters as harmful
objects which portended accidents to sight and
blindness." Without the aid of a telescope,
however, it's doubtful astrologers would have
associated this "cloud" with an obvious cluster,
such as the Pleiades. Today NGC 869 and 884 are
simply known as the Double Cluster in the
Sword Hand of Perseus.
One long-lived mystery concerning the
Double Cluster is why the 18th-century French
comet hunter Charles Messier did not include it
in his famous catalog. (Actually, Messier
probably had a good reason not to do so; see
Appendix Β for details). An equally compelling
mystery is that, while Hipparchus and other early
skywatchers listed NGC 869 and NGC 884 as two
objects, few of today's amateurs seem to believe
the components can be resolved with the unaided
eye. Most popular astronomy books and articles
state that the Double Cluster can be seen with the
unaided eye only as a hazy patch of light, which
becomes two beautiful objects with the aid of
binoculars or a rich-field telescope. With a sweep
of the hand that statement is true. But I wonder
how many observers have missed seeing two
distinct components with the unaided eye (not to
mention the brightest stars superposed on them)
because no one told them to look.
Together the two clusters occupy a full
degree of sky, and their bright cores are separated
by 25' — nearly a full Moon diameter. Why,
then, have these distinct cores escaped
The Caldwell Objects 63