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perihelion Line breaks: peri|he¦lion
Pronunciation: /ˌpɛrɪˈhiːlɪən/

Definition of perihelion in English:

noun (plural perihelia ˌpɛrɪˈhiːlɪə)

The point in the orbit of a planet, asteroid, or comet at which it is closest to the sun: today Mercury is at perihelion The opposite of aphelion.
More example sentences
  • He calculated to within a month the return in 1759 of Halley's comet to its perihelion (closest point to the Sun).
  • For objects orbiting Earth, periapsis and apoapsis are known as perigee and apogee; for objects orbiting the Sun, these locations are known as perihelion and aphelion.
  • This affects the climate because the influx of solar energy to our planet would then vary between perihelion and aphelion by a larger proportion than at present.


Mid 17th century: alteration of modern Latin perihelium (by substitution of the Greek inflection -on), from Greek peri- 'around' + hēlios 'sun'.

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