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The Caldwell Objects

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play begins at 8:00 p.m., when my eyes knock on<br />

the door of the northwestern horizon. If the night<br />

is clear, the door opens. And there, standing with<br />

perfect posture, is the matronly form of the<br />

Northern Cross. Dressed in the evening gown of<br />

the Milky Way, she welcomes me with open<br />

arms: "Why, Stephen, what a pleasant surprise!<br />

Come and join us!" Orion and his dogs suddenly<br />

burst through the back door of the southeastern<br />

horizon; winds lap at me like wet tongues,<br />

sending shivers up and down my spine. I look to<br />

the north and see three more friends, Cepheus,<br />

Cassiopeia, and Perseus, parading over the<br />

snowcapped hill of the celestial pole. My<br />

attention is drawn to Perseus because he carries a<br />

special gift wrapped in mist. <strong>The</strong> moment has<br />

come. I use my telescope, and the magic of<br />

magnification, to open the gift. <strong>The</strong> mist<br />

evaporates to reveal two crystal spheres. I look<br />

away from the telescope and see Perseus hanging<br />

them at the apex of the heavens. "If enough<br />

people wish for snow on Christmas day," he tells<br />

me, "their thoughts will shatter the crystal and<br />

the pieces will fall and turn to snow" As you can<br />

imagine, if snow did fall the next day I could see<br />

in it pieces of this shattered crystal glinting<br />

sharply in the morning light.<br />

It's not surprising that the Double Cluster<br />

could ignite a fire of imagination in a young<br />

skywatcher. Around the globe the great Double<br />

Cluster in Perseus is hailed as one of the most<br />

impressive telescopic sights in the heavens.<br />

Under dark skies the glow from this pair of<br />

stellar islands stretches across two Moon diameters<br />

and looks like a 4th-magnitude knot in the<br />

ruffled folds of the Milky Way, about halfway<br />

between Delta (δ) Cassiopeiae and Gamma (γ)<br />

Persei.<br />

Although Herschel is credited with discovering<br />

these objects' star-cluster nature, the<br />

combined glow of NGC 869 and NGC 884 has<br />

14<br />

been known since antiquity. Hipparchus recorded<br />

them as a "cloudy spot." In his book Star<br />

Names: <strong>The</strong>ir Lore and Meaning, Richard Hinckley<br />

Allen says that Ptolemy noted them as a "dense<br />

mass," and subsequent pretelescopic astronomers<br />

saw them as nebulous entities. Allen also says<br />

that the twin clusters "seem strangely to have<br />

escaped the notice of astrologers, who, as a rule,<br />

devoted much attention to clusters as harmful<br />

objects which portended accidents to sight and<br />

blindness." Without the aid of a telescope,<br />

however, it's doubtful astrologers would have<br />

associated this "cloud" with an obvious cluster,<br />

such as the Pleiades. Today NGC 869 and 884 are<br />

simply known as the Double Cluster in the<br />

Sword Hand of Perseus.<br />

One long-lived mystery concerning the<br />

Double Cluster is why the 18th-century French<br />

comet hunter Charles Messier did not include it<br />

in his famous catalog. (Actually, Messier<br />

probably had a good reason not to do so; see<br />

Appendix Β for details). An equally compelling<br />

mystery is that, while Hipparchus and other early<br />

skywatchers listed NGC 869 and NGC 884 as two<br />

objects, few of today's amateurs seem to believe<br />

the components can be resolved with the unaided<br />

eye. Most popular astronomy books and articles<br />

state that the Double Cluster can be seen with the<br />

unaided eye only as a hazy patch of light, which<br />

becomes two beautiful objects with the aid of<br />

binoculars or a rich-field telescope. With a sweep<br />

of the hand that statement is true. But I wonder<br />

how many observers have missed seeing two<br />

distinct components with the unaided eye (not to<br />

mention the brightest stars superposed on them)<br />

because no one told them to look.<br />

Together the two clusters occupy a full<br />

degree of sky, and their bright cores are separated<br />

by 25' — nearly a full Moon diameter. Why,<br />

then, have these distinct cores escaped<br />

<strong>The</strong> <strong>Caldwell</strong> <strong>Objects</strong> 63

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