| 释义 |
ˈprotoplanet Astr.
[f. proto- + planet n.1]
A large diffuse body of matter in a solar or stellar orbit, postulated as a preliminary stage in the evolution of a planet.
1949Astrophysical Jrnl. CIX. 309 A simple model is therefore considered first, consisting of two spherical masses (‘protoplanets’) in near contact, located inside the gaseous disk surrounding the sun. 1952H. C. Urey Planets i. 13 First, a spherical or irregular cloud must rapidly collapse to a flat disk... Second, the disk of gas would break up into a Kolmogoroff spectrum of turbulent eddies... Finally a system of protoplanets, one for each of the planets, would be left at the appropriate distance from the sun. 1971I. G. Gass et al. Understanding Earth ix. 135/2 This conclusion suggests..that a considerable degree of fractionation had already taken place in the protoplanet before it condensed into a solid body. 1974Sci. Amer. Mar. 57/3 The second compositional class would have consisted of protoplanets formed just after the metallic iron-nickel alloy condensed out of the solar nebula.
Hence protoˈplanetary a., of, pertaining to, or being a protoplanet.
1962Lancet 13 Jan. 89/1 Meteorites are generally assumed to have originated by the disruption of protoplanetary bodies in the region now occupied by the asteroids. 1977Nature 13 Oct. 584/1 When the cloud collapses and a new hot star is created in its centre, the flattened protoplanetary disk formed from the remnants of the cloud continues to be cold. |