The point in the orbit of a planet, asteroid, or comet at which it is furthest from the sun.‘Mars is at aphelion’The opposite of perihelion
- ‘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.’
- ‘This is because at aphelion the planet is moving slowest, and consequently it is less likely to pass across the Sun during the critical window.’
- ‘There are small cyclic variations in those apparent sizes because the Earth-Moon distance changes as the latter moves between perigee and apogee, and the Earth-Sun separation alters as the former moves between perihelion and aphelion.’
- ‘Variations in the timing of perihelion and aphelion are caused by a ‘wobbling’ in the Earth's axis of rotation as it rotates around the Sun.’
- ‘Furthermore, any resonance with the Earth is illusory in that Mercury is not well placed for observations except during its brief greatest elongations near its aphelion.’
Mid 17th century alteration of modern Latin aphelium (by substitution of the Greek inflection -on), from Greek aph' hēlion ‘from the sun’.
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