Astr. Pl. aphelia. [Græcized form of mod.L. aphēlium, f. Gr. ἀφ’ = ἀπό off, from + ἤλιος sun; formed, by Kepler, after the apogæum, ἀπόγαιον, of the Ptolemaic astronomy (see Prodr. dissert. cosmographicarum, 1596, and Epitome astronom. Copernic. 1618). Aphelium was also the earlier form in Eng.; cf. PARHELION, Gr. παρήλιον. Fr. has aphélie, like apogée.]
1. That point of a planet’s or comet’s orbit at which it is farthest from the sun.
1656. trans. Hobbes’s Elem. Philos. (1839), 443. The apogæum of the sun or the aphelium of the earth ought to be about the 28th degree of Cancer.
1676. Halley, in Rigaud, Corr. Sci. Men, I. 237. The Aphelion, Eccentricities, and Proportions of the Orbs of the Primary Planets.
1794. Sullivan, View Nat., II. 410. Of these distances, the least of all is called the perihelium, and the greatest the aphelium.
1837. Whewell, Hist. Induct. Sc. (1857), II. 131. The aphelia of Mercury, Venus, the Earth, and Mars, slightly progress.
1880. Wallace, Isl. Life, viii. 132. The effect is intensified by winter being there in aphelion.
2. fig.
1845. H. Rogers, Ess., I. iii. 137. The dark aphelion of the eccentric orbit in which the church of Christ had wandered.
1858. Gen. P. Thompson, Audi Alt., II. lxxvi. 29. France, which is just now in what astronomers call the aphelion or furthest point of political cold.
