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.
| 1949 Astrophysical 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. 1952 H. 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. 1971 I. 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. 1974 Sci. 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.
| 1962 Lancet 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. 1977 Nature 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. |