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The Caldwell Objects

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94<br />

which is best seen with high magnification.<br />

From a dark-sky site the cluster appears to be<br />

snared within a web of dark nebulosity. Throw<br />

the low-power image slightly out of focus and<br />

see if the region southwest of the pyramid<br />

appears especially dark. Perhaps a dust cloud<br />

has dimmed starlight here.<br />

At 72x the cluster fractures into smaller<br />

groupings, even as the pyramid remains bold<br />

and bright. <strong>The</strong> pendant containing HD 111973<br />

reveals at least seven stars that form a smaller<br />

pyramid at right angles to the larger, brighter<br />

one. HD 111973 looks yellow at 72x, as does HD<br />

111904, the magnitude-5.8 star at the<br />

northwestern corner of the large, bright pyramid.<br />

In February 1997 and again in April 2000, HD<br />

111973 appeared at least a half magnitude (60<br />

percent) brighter than HD 111904 to my eyes —<br />

even though, according to the second edition of<br />

Sky Catalogue 2000.0, it should be 0.1 magnitude<br />

(10 percent) fainter. An undated drawing by<br />

Kenneth Glyn Jones in Volume 7 of the Webb<br />

Society Deep-Sky Observer's Handbook (published<br />

in 1987) shows HD 111973 signifi-candy fainter<br />

than HD 111904, and this observation was based<br />

on a view through a 12-inch reflector. Most<br />

photographs I've seen show HD 111973 fainter<br />

than HD 111904, but that may be an artifact of<br />

the photographic emulsions. (Note, by the way,<br />

that in both Ernst Hartung's and Robert<br />

Burnham Jr.'s handbooks the photographs of the<br />

cluster have been flopped, with east and west<br />

reversed.) Clearly these stars warrant watching.<br />

At 72x in the 4-inch SAO 252073 looks more<br />

orange than red to me. It is the northeasternmost<br />

star in a tiny line of three similarly<br />

bright stars oriented northeast to southwest.<br />

SAO 252073, to my eyes, is the faintest of these<br />

three stars. Glyn Jones, however, saw it as the<br />

brightest. My eyes tend to be blue-sensitive<br />

380<br />

while other observers are more sensitive to red<br />

light, so this apparent discrepancy might be<br />

related to the way different observers perceive<br />

color, and not to any real brightness variations.<br />

Yet Edward James Stone, Her Majesty's Astronomer<br />

at the Cape from 1870 to 1879, suspected<br />

that this red star had altered its brightness since<br />

John Herschel had observed it. And the Hipparcos<br />

satellite's database seems to support the<br />

notion, for on its watch the star's apparent visual<br />

magnitude appears to have ranged from 7.08 to<br />

7.52. However, Hipparcos didn't enable<br />

astronomers to determine a period of variability<br />

or to classify the star's light curve. Clearly it<br />

would behoove someone with a photometer to<br />

monitor all the Jewel Box's supergiant suns for<br />

variability.<br />

Moderate magnification reveals other<br />

treasures in the Jewel Box. <strong>The</strong> brightest stars to<br />

the southwest of the large pyramid form two<br />

semicircles, like wide crowns, facing in opposite<br />

directions: one opens to the north-northwest and<br />

the other to the southeast. Immediately south of<br />

these crowns is a long chain of fainter suns<br />

oriented in the same northwest-to-southeast<br />

direction as the two semicircles. <strong>The</strong> void<br />

between these groupings may be a long lane of<br />

dust.<br />

At high power the cluster fractures completely<br />

and the Jewel Box loses its luster. Most<br />

prominent is HD 111973 and the pyramidal<br />

pendant. Look for a black cross at the southwestern<br />

edge of the pyramid. Look also for a<br />

tight double star immediately northwest of HD<br />

111973 and another about 2' to the southeast. For<br />

a slightly greater challenge, see if you can detect<br />

a red, 13th-magnitude star south of SAO 252073.<br />

It is one that John Herschel first noticed, along<br />

with so many others of the Jewel Box's sparkling<br />

gems (though he didn't say how far south of SAO<br />

252073 it is).<br />

Deep-Sky Companions: <strong>The</strong> <strong>Caldwell</strong> <strong>Objects</strong>

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