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单词 the coal sack
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the Coal Sack
2. Astronomy. A dark nebula giving the appearance of a gap in the stars of the Milky Way; spec. (usually the Coal Sack) one near the Southern Cross (formerly also called Black Magellanic Cloud).
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1844 E. O. Kendall Uranography 184 The Magellanic Clouds, which are also called the Cap-clouds and the Coal-sacks, are three dark spots in the bright part of the Milky-way by the Southern Cross.
1847 J. F. W. Herschel Results Astron. Observ. iv. 384 That singular vacuity on the south following side of the cross, called the ‘Coal-sack’, a pear-shaped oval, whose greatest length is about 8°, and breadth 5°.
1870 R. A. Proctor Other Worlds than Ours xi. 264 In the southern Coal-sack there are minute telescopic stars.
1940 G. Gamow Birth & Death of Sun ix. 188 Two well-known dark holes in the Milky Way, named the ‘Coal Sacks’ by astronomically inclined seamen.
1993 D. Malin View of Universe v. 94 The Coalsack is also used..as an informal measure of the darkness and transparency of the night sky.
2007 S. R. Coe Nebulae x. 91 My most memorable observation of the Coal Sack is from the deck of the cruise ship Dawn Princess off the coast of South America, waiting for a solar eclipse.
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更新时间:2024/12/24 7:56:58