different between perigee vs aphelion

English

Etymology

From French périgée via Latin perigeum, perigaeum, ultimately from Ancient Greek ???? (perí, “near”) + ?? (gê, “Earth”).

Pronunciation

• (UK) IPA^(key): /?p???d?i?/
• (US) IPA^(key): /?p???d?i/

Noun

perigee (plural perigees)

1. (astronomy) The point, in an orbit about the Earth, that is closest to the Earth: the periapsis of an Earth orbiter.
2. (astronomy, more generally) The point, in an orbit about any planet, that is closest to the planet: the periapsis of any satellite.
   • 1995, John H. Rogers, The Giant Planet Jupiter, Cambridge University Press, ?ISBN, page 335:

     Conjunctions of I and II [Io and Europa] occur when they are near perigee and apogee respectively; conjunctions of II and III [Europa and Ganymede] occur when II [Europa] is near perigee.

   • 2002, Serge Brunier, Solar System Voyage, Cambridge University Press, ?ISBN, page 36:

     The resolution of the images obtained by this American probe [Messenger] will depend on its altitude [above Mercury] at any one time: about ten meters at perigee (200km altitude), but only one 1 km at apogee (15000km).

   • 2010, Ruth Walker and Mary M. Shaffrey et al., Exploring Space: The High Frontier, Jones & Bartlett Learning, ?ISBN, page 129:

     [Nereid’s] apogee—farthest point from Neptune—is five times the distance of its perigee—its closest point.

3. (possibly archaic outside astrology) The point, in any trajectory of an object in space, where it is closest to the Earth.

Antonyms

• apogee

Hyponyms

• proxigee

Derived terms

• perigee moon

Related terms

• see periapsis

Translations

See also

• periapsis, periastron, perihelion

English

Etymology

Greek form of Latin aphelium, from Ancient Greek ??? (apó, “from”) + ????? (h?lios, “sun”) (modelled after apogaeum). Compare perihelion.

Pronunciation

• IPA^(key): /??fi?l??n/, /æp?hi?l??n/

Noun

aphelion (plural aphelia or (deprecated) aphelions)

1. (astronomy) The point in the elliptical orbit of a planet, comet, etc., where it is farthest from the Sun.

Antonyms

• perihelion

Related terms

• see apoapsis

Translations

Anagrams

• Ophelian