The point in the orbit of a planet, asteroid, or comet at which it is closest to the sun.The opposite of aphelion
- ‘The radius vector is shortest when the planet is at perihelion and longest at aphelion.’
- ‘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 problem involved the advance of the perihelion of the planet Mercury.’
- ‘He calculated to within a month the return in 1759 of Halley's comet to its perihelion (closest point to the Sun).’
Mid 17th century: alteration of modern Latin perihelium (by substitution of the Greek inflection -on), from Greek peri- ‘around’ + hēlios ‘sun’.
We take a look at several popular, though confusing, punctuation marks.