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The Caldwell Objects

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98 & 99<br />

Dim: 7° x 5°<br />

Dist: 610 light-years and 790 light-years (two overlapping<br />

nebulae)<br />

Disc: Known since antiquity<br />

T HE C OALSACK (CALDWELL 99), A RIVAL OF<br />

Crux though devoid of its splendor, is the Milky<br />

Way's poster child for visual mystery. <strong>The</strong><br />

northern tip of the kite-shaped dark nebula lies<br />

due south of the Jewel Box (<strong>Caldwell</strong> 94), while<br />

its western flank washes against Acrux, the foot<br />

of the Cross. In photographs the Coalsack's size<br />

and shape mimic that of the Cross's interior, so I<br />

like to call it the Shadow of the Cross. Australian<br />

aborigines have probably known of this dark<br />

cloud for more than 40,000 years; it appears, on<br />

tribal bark paintings from Groote Eylandt, as a<br />

speared fish being held up by two brothers over<br />

two fires (the brothers and their fires representing<br />

the four stars of the Cross). Another Australian<br />

legend refers to the Coal-sack as "the<br />

embodiment of evil in the shape of an Emu." <strong>The</strong><br />

Polynesians knew it as Te Paniwi a Taewa, a<br />

black fish. And ancient Peruvians perceived it as<br />

the celestial Doe suckling its fawn. In more<br />

modern times the Coal-sack was Amerigo<br />

Vespucci's Il Canopo fosco (the dark Canopus) and<br />

Adm. William Henry Smyth's Black Magellanic<br />

Cloud. In his Oceana, the 19th-century historian<br />

James Anthony Froude called it "the inky spot —<br />

an opening into the awful solitude of unoccupied<br />

space."<br />

Froude's remark reflects William Herschel's<br />

pronouncement that each starless void was a<br />

Loch im Himmel, an opening in the heavens, a<br />

curious vacancy "through which we seem to gaze<br />

into an uninterrupted infinity." In his sweeps of<br />

the night sky, Herschel found a remarkable<br />

coincidence: the blackest voids appeared near the<br />

richest star clusters, which "would almost<br />

authorise a suspicion that the<br />

392<br />

J. H ERSCHEL: None.<br />

GC/NGC: None.<br />

stars, of which it is composed, were collected<br />

from that place, and had left the vacancy." <strong>The</strong><br />

elder Herschel specifically cited the black void<br />

near Rho (ρ) Ophiuchi and the globular cluster<br />

M80 as a magnificent example. Had he spied the<br />

Coalsack and its proximity to the Jewel Box —<br />

not to mention the open cluster NGC 4609<br />

(<strong>Caldwell</strong> 98) within it — his suspicions would<br />

have been magnified.<br />

From South Africa in 1834 Herschel's son,<br />

John, turned his attention to his father's "holes."<br />

At first he presumed them to be "tubular<br />

vacancies" penetrating the depths of space. He<br />

later retracted this view. But scholars like Froude<br />

and authors like Thomas Hardy carried William<br />

Herschel's fantastic view of these voids into the<br />

late 19th century. In his novel Two on a Tower — a<br />

work Hardy created "to set the emotional history<br />

of two infinitesimal lives against the stupendous<br />

background of the stellar universe" — we find<br />

astronomer Swithin St. Cleeve showing the sky<br />

to his imminent lover, Lady Constantine, to<br />

whom he tries to explain the unfathomable size<br />

of the universe:<br />

. . . horrid monsters lie up there waiting to<br />

be discovered by any moderately penetrat-<br />

ing mind ____ Impersonal monsters, namely,<br />

Immensities. Until a person has thought out the stars<br />

and their inter-spaces, he has hardly learnt that there<br />

are things much more terrible than monsters of<br />

shape, namely, monsters of magnitude without<br />

known shape. Such monsters are the voids and waste<br />

places of the sky. Look, for instance, at those pieces of<br />

darkness in the Milky Way.... You see that dark<br />

opening in<br />

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

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