aphelion

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English[edit]

Etymology[edit]

PIE word
*h₂epó
PIE word
*sóh₂wl̥
A diagram showing Earth at its aphelion (position 1) and perihelion (position 2) in its orbit around the Sun (3).

A Greek form of New Latin aphēlium (whence English aphelium, now displaced), from Ancient Greek ἀπο- (apo-, prefix meaning ‘away, from, off’) + ἥλῐος (hḗlios, the sun) (ultimately from Proto-Indo-European *sóh₂wl̥ (the sun)) + -ον (-on, suffix forming some nouns), modelled after New Latin apogaeum (apogee).[1]

The plural form aphelia is from aphelion + -a (plural form of the suffix -on).

Pronunciation[edit]

Noun[edit]

aphelion (plural aphelia or (deprecated) aphelions)

  1. (astronomy, also figuratively) The point in the elliptical orbit of a comet, planet, or other astronomical object, where it is farthest from the Sun.
    Antonym: perihelion
    • 1837, William Whewell, “The Inductive Epoch of Newton—Discovery of the Universal Gravitation of Matter, according to the Law of the Inverse Square of the Distance”, in History of the Inductive Sciences, from the Earliest to the Present Times. [], volume II, London: John W[illiam] Parker, []; Cambridge, Cambridgeshire: J. and J. J. Deighton, →OCLC, book VII (History of Physical Astronomy), page 170:
      [I]t follows from the theory of gravity, that the aphelia of Mercury, Venus, the Earth, and Mars, slightly progress.

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Translations[edit]

References[edit]

  1. ^ aphelion, n.”, in OED Online Paid subscription required, Oxford, Oxfordshire: Oxford University Press, December 2021; “aphelion, n.”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.

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