perihelion

Definition

The point in the elliptical orbit of a comet, planet, etc., where it is nearest to the Sun.

Etymology

PIE word *sóh₂wl̥ From perihelium (“perihelion”) (obsolete) + -ion (suffix used for other names of apsides). Perihelium is borrowed from Late Latin perihelium, from Ancient Greek περι- (peri-, “around; surrounding”), ultimately from Proto-Indo-European *per- (“before, in front; first”)) + ἥλιος (hḗlios, “sun”) (ultimately from Proto-Indo-European *sóh₂wl̥ (“sun”)), which was modelled after perigeum (“point in an orbit about the Earth that is closest to the Earth, perigee”).

Example Sentences

• "The æquation of the Earth encreaſeth from her Aphelion, until ſhe come to the point where it's greateſt, and from thence it again decreaſeth till ſhe come to her Perihelion, or oppoſite Auge: in like manner it increaſeth from her Perihelion to the point where it's greateſt, and afterwards decreaſeth till ſhe come againe to the Auge or Aphelion, [...]"
• "They [the best astronomers of this age] all agree that the Planets turn in ſo many Ellipſes, of which the Sun is the focus; the reaſon of it is, that they are obſerved to be in ſome points called Perihelia, nearer to the Sun, and, in the oppoſite points call'd Aphelia, farther from it; which could not be, if they mov'd in a perfect circle."
• "[I]f Comets were obſerv'd to have to Atmoſphere after their return from the Regions beyond Saturn, before they arrived at their Perihelia again, then indeed this reaſoning were unavoidable; but ſeeing the contrary is evident from Aſtronomical Obſervations, it cannot affect his [William Whiston's] Hypotheſis."