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[uh-fee-lee-uh n, uh-feel-yuh n, ap-hee-lee-uh n] /əˈfi li ən, əˈfil yən, æpˈhi li ən/
noun, plural aphelia
[uh-fee-lee-uh, uh-feel-yuh, ap-hee-lee-uh] /əˈfi li ə, əˈfil yə, æpˈhi li ə/ (Show IPA)
Astronomy. the point in the orbit of a planet or a comet at which it is farthest from the sun.
Compare perihelion.
Origin of aphelion
1650-60; Hellenized form of New Latin aphēlium < Greek *aphḗlion (diástēma) off-sun (distance), neuter of *aphḗlios (adj.), equivalent to ap- ap-2 + hḗli(os) sun + -os adj. suffix. See apogee
Related forms
aphelian, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for aphelion
Historical Examples
  • The planet consequently receives nearly three times as much light and heat in perihelion as in aphelion.

    The Asteroids Daniel Kirkwood
  • In the orbit of a planet, means the line joining its aphelion and perihelion.

    The Sailor's Word-Book William Henry Smyth
  • The imaginary line joining the aphelion and perihelion points in the orbit of a planet.

    The Sailor's Word-Book William Henry Smyth
  • The motion of Newton's comet at aphelion may be equally slight.

  • It may, perhaps, be far advanced in its aphelion,—but when to return?

  • After the fourth go round he was fully five diameters out at aphelion.

    The Pirates of Ersatz Murray Leinster
  • At present the earth is about three millions of miles nearer the sun in perihelion than in aphelion.

    The Prehistoric World E. A. Allen
  • It will not return before the 38th century, and will only reach its aphelion about the year 2800.

    Comets and Meteors Daniel Kirkwood
  • At the perihelion the planet is urged from the sun and at the aphelion towards the sun.

  • It seems probable, then, that in all northern lands glaciation would commence when autumn occurred in aphelion.

    Island Life Alfred Russel Wallace
British Dictionary definitions for aphelion


/æpˈhiːlɪən; əˈfiː-/
noun (pl) -lia (-lɪə)
the point in its orbit when a planet or comet is at its greatest distance from the sun Compare perihelion
Derived Forms
aphelian, adjective
Word Origin
C17: from New Latin aphēlium (with pseudo-Greek ending -ion) from ap- + Greek hēlios sun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for aphelion

"point farthest from the sun" (of a celestial body's orbit), 1670s, a Grecianized form of Modern Latin aphelium, altered by Johannes Kepler based on Greek apo heliou "away from the sun," from apo "away from" (see apo-) + heliou, genitive of helios "sun" (see sol). The whole was formed on the model of Ptolemaic apogaeum (see apogee) to reflect the new helio-centric model of the universe.

Online Etymology Dictionary, © 2010 Douglas Harper
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aphelion in Science

The point at which an orbiting body, such as a planet or comet, is farthest away from the Sun. Compare apogee, perihelion.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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