English astronomer Sir William Herschel (1738–1822) may have been the first to catalog this “hole in the heavens,” as he put it. It became a commonly known feature by the late 19th century, as British author Thomas Hardy alluded to it in his 1882 novel,
Two on a Tower; in it, Swithin St. Cleeve points out the bleak region to his lover, Lady Constantine: “You see that dark opening in [the Milky Way] near the Swan? There is a still more remarkable one south of the equator, called the Coal Sack, as a sort of nickname that has a farcical force from its very inadequacy.”
But where in the Swan did Swithin see it?
Garrett P. Serviss told us clearly in his 1888
Astronomy with an Opera-Glass: “Between the stars α, γ, ε,” he explained, “is the strange dark gap in the galaxy called the Coal-Sack, a sort of hole in the starry heavens.” Richard Hinckley Allen confirmed this position in his 1899
Star-Names and Their Meanings; he then went on to formally call this “almost vacant space” the “Northern Coal-sack.”
Alas, Serviss muddied the waters a little in his 1910 book,
Round the Year with the Stars, when he said, “Around and above the head of the cross there are dark spaces, which are specially impressive when the eyes are partly averted from them.”
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