| 释义 |
‖ nebula|ˈnɛbjʊlə|
Pl. nebulæ |-iː|.
[L. nebula mist, vapour, related to Gr. νεϕέλη, OHG. nebul (G. nebel).]
1. a. A film upon, or covering, the eye; spec. a clouded speck or spot on the cornea causing defective vision.
1661Lovell Hist. Anim. & Min. Isagoge b 5 The Raie hath a long and rough taile, the eye is covered with a nebula. 1719Quincy Phys. Dict. (1722), Nebula..is figuratively applied to Appearances..in the human Body, as to Films upon the Eyes. 1836–9Todd's Cycl. Anat. II. 177/2 Slight opacities, or nebulæ, as they are called, if confined to the conjunctival covering of the cornea. 1844H. Stephens Bk. Farm II. 229 Farm-horses..being liable to accidents, the effects of inflammation,—nebulæ, or specks,—do sometimes occur. 1895Swanzy Diseases Eye (ed. 5) 150 The opacity..is called a nebula.
b. A cloudy or flocculent appearance.
1805S. Weston Werneria 70 Quartz is distinguishable from glass by the nebulæ, or appearance of clouds in its transparency. 1846Day tr. Simon's Anim. Chem. II. 184 When the temperature is sufficiently elevated, the coagulation begins to occur in the form of small white nebulæ.
2. fig. A misty or obscure affair. rare—1.
a1734North Exam. ii. iv. §147 (1740) 310 He, that could pass over the Items of the Grand Plot without Notice, will not amuse the Reader with these Nebulæ.
3. Astron. An indistinct cloud-like cluster of distant stars, or a luminous patch of supposed gaseous or stellar matter lying beyond the limits of the solar system. In mod. use the term is applied to (a) a cloud of gas or dust situated within the interstellar space of a galaxy (usu. our own) and appearing as either a bright or a dark cloud (according to whether or not there are stars present to make it luminous); (b) a galaxy (usu. one other than our own).
1727–38Chambers Cycl. s.v. Stars, Nebulous stars, being such as only appear faintly, in clusters, in the form of little lucid nebulæ or clouds. 1781Gentl. Mag. LI. 526 This..nebula was discovered March 23, 1779. 1802Herschel in Phil. Trans. XCII. 499 A stellar nebula..may be a real cluster of stars. Ibid. 523 It is of a middle species, between the planetary nebulæ and nebulous stars. 1841Brewster Mart. Sci. ii. 31 Upon directing his telescope to nebulæ and clusters of stars. 1873Dawson Earth & Man i. 8 The spectroscope has.. shown that some nebulæ are actually gaseous. 1924H. Dingle Mod. Astrophysics xvi. 302 A dark nebula is really dark, and not merely too faint for its light to be seen on account of its great distance from us. 1930R. H. Baker Astron. xi. 465 Frequently a ‘nebula’ turned out to be a star-cluster, thereby encouraging the opinion, in former times, that all nebulae are really clusters of stars. Ibid., Modern investigations have shown that nebulae, as distinguished from ordinary star-clusters, fall into two classes having entirely different characteristics, namely, the galactic nebulae and the extra-galactic nebulae. 1963B. & J. Lovell Discovering Universe ix. 114 The Milky Way system is typical of many extra-galactic spiral nebulae, and very much akin to M31 in Andromeda. 1968P. Moore Sky at Night II. xxxii. 232 With other nebulæ, there are no convenient stars—and so the nebulæ cannot be seen directly, but betray themselves because they blot out the light of the stars beyond... Mention should also be made of the nebulæ which shine by pure reflection. Such is the nebula in the Pleiades. Ibid. 235 The old term of ‘spiral nebula’ has become obsolete, to be replaced by ‘spiral galaxy’; a proper nebula is gaseous, and belongs to the Galaxy in which we live. 1971D. W. Sciama Mod. Cosmol. iii. 39 In this way he [sc. E. P. Hubble] obtained a distance of 800,000 light-years for the Andromeda nebula, and similar values for other spiral nebulae. Now that these nebulae are well established as stellar systems outside our own, we shall henceforth call them galaxies. 1974F. W. Cole Fund. Astron. xiii. 358/1 The Orion nebula is 1600 LY distant and about 30 LY in diameter. In our galaxy, other emission nebulae of the same type are about the same size. Vastly larger emission nebulae are known outside our galaxy; an excellent example is in M33, a spiral galaxy in Triangulum.
b. transf. and fig.
1817J. Adams Wks. (1856) X. 245 Hutchinson and all his nebula of stars and satellites. 1856Miss Mulock J. Halifax xii, The world of existence to him seemed to have lazily melted down into a mere nebula. 1880Disraeli Endym. xxix, The present was too hard for him, and his future was only a chaotic nebula.
c. attrib., as nebula hypothesis, nebula line, nebula photography, etc. Also in pl. as nebulæ spectrum.
1877Nature XVI. 401/2 The brightest line of the nebulæ spectrum. Ibid. 414/1 If we accept the bright line..to be veritably the chief nebula line. a1891Anthony's Photogr. Bull. IV. 363 His primary object was to use it for nebula photography. 1892A. Taylor in Photogr. Ann. II. 116 The central nucleus..demanded by Laplace's nebula hypothesis.
4. Fog, mist.
1894W. C. Ley Cloudland 33 The spherules of water which constitute nebula vary greatly in diameter. Ibid. 35 Nebula must not..be regarded as in all cases a very local phenomenon. |