| 释义 |
Roche, n.4 Astron.|rəʊʃ|
The name of Edouard Albert Roche (1820–83), French mathematician, used attrib. and in the possessive to denote concepts arising out of his work, as Roche('s) limit, (a) the closest distance to which a self-gravitating body (strictly a fluid body: see quot. 1900) can approach a more massive body without being pulled apart by the gravitational field of the latter body; (b) the smallest continuous equipotential surface (having the form of two lobes meeting at a point) which can exist around both members of a system of two gravitating bodies, spec. a binary star system; Roche lobe, either of the two volumes of space (meeting at a point) that are bounded by Roche's limit (b) in a binary system; Roche zone, the region of space within Roche's limit (sense (a)).
1889G. H. Darwin in Harper's Mag. June 73/1 The distance of..2·44 of a planet's radius I call Roche's limit for that planet. 1900Astrophysical Jrnl. XI. 122 In the derivation of Roche's limit the assumption was made that the satellite was a perfectly homogeneous incompressible fluid, and that its rotation and revolution were performed in the same period. 1930R. H. Baker Astron. v. 212 All parts of Saturn's rings lie within Roche's limit. 1959Z. Kopal Close Binary Syst. iii. 133 Such configurations represent the largest closed equipotentials capable of containing the whole mass of the respective components, and will hereafter be referred to as their Roche limits. 1969Times 10 July 12/8 If the moon had ever come within a critical distance of earth, known as the Roche limit, the tidal forces raised by the earth would have disrupted it. 1972W. Strohmeier Variable Stars vii. 182 Expansion of the components in close binaries towards their Roche limits, in a time scale of 106 years, can also give rise to an exchange between the rotational and orbital momenta. 1974Sci. Amer. Feb. 53/1 Only a body with more than gravitational cohesion can withstand the tidal effects within Roche's limit.
[1960Astrophysical Jrnl. CXXXII. 149 (caption) The radii of the Roche-limit lobes for a mass ratio of unity.] 1969Ibid. CLVIII. 571 Morton concluded that on such a time scale the contact component would be stable, shrinking within the Roche lobe after initial mass loss. 1975Sci. Amer. Mar. 30/3 In the evolution of a typical binary, as soon as one of the components expands to a volume larger than that of its Roche lobe the matter outside the lobe will begin to flow toward the companion star.
1971I. G. Gass et al. Understanding Earth vii. 112/2 What would happen if the Moon were to enter the Roche zone? 1978New Scientist 23 Nov. 607/2 One or more former moons of Uranus spiralled into the planet's Roche zone where they broke up because of tidal forces, producing the parent fragments of the rings. |