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
- ‘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.’
- ‘The radius vector is shortest when the planet is at perihelion and longest at aphelion.’
- ‘The problem involved the advance of the perihelion of the planet Mercury.’
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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