periapsis

English

In a 2-body system in which the objects each follow an elliptical orbit around the system's centre of mass, the apsides are: the farthest point, or apoapsis, and the point of closest approach, or periapsis.

Etymology

peri- + apsis.

Noun

periapsis (plural periapsides or periapsises or periapses)

  1. (astronomy, astrophysics) The point of a body's (elliptical) orbit in a 2-body gravitational system such that the distance between the two bodies (measured from their respective centres of mass) is at its minimum.
    • 1983, Richard O. Fimmel, Laurence Colin, Eric Burgess, Pioneer Venus, NASA SP-461, page 109,
      Figure 5-19. Sun-Venus-Orbiter geometry illustrates how the periapsis moves around the planet during the Venusian sidereal year to sample day and night hemispheres. Because the planet rotates in a retrograde direction, it takes more than one Venusian sidereal year for periapsis to move over all longitudes of the planet (as explained in text).
    • 2001, D. A. Vallado, Fundamentals of Astrodynamics and Applications, Springer, page 325:
      We don't always want to burn near periapsis. Suppose we want to change the height at periapsis. The most efficient place to change the radius of periapsis is at apoapsis. Consider applying at some other point in the orbit. In this case both periapsis and apoapsis will change. If we apply the tangentially at apoapsis, all of the will go into changing periapsis, and vice versa.
    • 2004, R. S. Saunders, et al., Mars Odyssey Mission, C. T. Russell (editor), 2001 Mars Odyssey, Kluwer Academic Publishers, page 34,
      The main aerobraking phase began once the point of the spacecraft's periapsis had been lowered to within 110 km above the Martian surface.
  2. The minimum distance between the two bodies in such a system.

Usage notes

  • In the case of some particular celestial bodies, specialized terms are used. See Related terms, below, for examples.

Synonyms

Antonyms

Hypernyms

Derived terms

  • argument of periapsis
  • longitude of periapsis

Translations

Further reading

Finnish

Etymology

Internationalism (see English periapsis).

Pronunciation

  • IPA(key): /ˈperiɑpsis/, [ˈpe̞riˌɑ̝ps̠is̠]
  • Rhymes: -ɑpsis
  • Syllabification(key): pe‧ri‧ap‧sis

Noun

periapsis

  1. (astronomy) periapsis

Declension

Inflection of periapsis (Kotus type 39/vastaus, no gradation)
nominative periapsis periapsikset
genitive periapsiksen periapsisten
periapsiksien
partitive periapsista periapsiksia
illative periapsikseen periapsiksiin
singular plural
nominative periapsis periapsikset
accusative nom. periapsis periapsikset
gen. periapsiksen
genitive periapsiksen periapsisten
periapsiksien
partitive periapsista periapsiksia
inessive periapsiksessa periapsiksissa
elative periapsiksesta periapsiksista
illative periapsikseen periapsiksiin
adessive periapsiksella periapsiksilla
ablative periapsikselta periapsiksilta
allative periapsikselle periapsiksille
essive periapsiksena periapsiksina
translative periapsikseksi periapsiksiksi
abessive periapsiksetta periapsiksitta
instructive periapsiksin
comitative See the possessive forms below.
Possessive forms of periapsis (Kotus type 39/vastaus, no gradation)
first-person singular possessor
singular plural
nominative periapsikseni periapsikseni
accusative nom. periapsikseni periapsikseni
gen. periapsikseni
genitive periapsikseni periapsisteni
periapsiksieni
partitive periapsistani periapsiksiani
inessive periapsiksessani periapsiksissani
elative periapsiksestani periapsiksistani
illative periapsikseeni periapsiksiini
adessive periapsiksellani periapsiksillani
ablative periapsikseltani periapsiksiltani
allative periapsikselleni periapsiksilleni
essive periapsiksenani periapsiksinani
translative periapsiksekseni periapsiksikseni
abessive periapsiksettani periapsiksittani
instructive
comitative periapsiksineni
second-person singular possessor
singular plural
nominative periapsiksesi periapsiksesi
accusative nom. periapsiksesi periapsiksesi
gen. periapsiksesi
genitive periapsiksesi periapsistesi
periapsiksiesi
partitive periapsistasi periapsiksiasi
inessive periapsiksessasi periapsiksissasi
elative periapsiksestasi periapsiksistasi
illative periapsikseesi periapsiksiisi
adessive periapsiksellasi periapsiksillasi
ablative periapsikseltasi periapsiksiltasi
allative periapsiksellesi periapsiksillesi
essive periapsiksenasi periapsiksinasi
translative periapsikseksesi periapsiksiksesi
abessive periapsiksettasi periapsiksittasi
instructive
comitative periapsiksinesi
first-person plural possessor
singular plural
nominative periapsiksemme periapsiksemme
accusative nom. periapsiksemme periapsiksemme
gen. periapsiksemme
genitive periapsiksemme periapsistemme
periapsiksiemme
partitive periapsistamme periapsiksiamme
inessive periapsiksessamme periapsiksissamme
elative periapsiksestamme periapsiksistamme
illative periapsikseemme periapsiksiimme
adessive periapsiksellamme periapsiksillamme
ablative periapsikseltamme periapsiksiltamme
allative periapsiksellemme periapsiksillemme
essive periapsiksenamme periapsiksinamme
translative periapsikseksemme periapsiksiksemme
abessive periapsiksettamme periapsiksittamme
instructive
comitative periapsiksinemme
second-person plural possessor
singular plural
nominative periapsiksenne periapsiksenne
accusative nom. periapsiksenne periapsiksenne
gen. periapsiksenne
genitive periapsiksenne periapsistenne
periapsiksienne
partitive periapsistanne periapsiksianne
inessive periapsiksessanne periapsiksissanne
elative periapsiksestanne periapsiksistanne
illative periapsikseenne periapsiksiinne
adessive periapsiksellanne periapsiksillanne
ablative periapsikseltanne periapsiksiltanne
allative periapsiksellenne periapsiksillenne
essive periapsiksenanne periapsiksinanne
translative periapsikseksenne periapsiksiksenne
abessive periapsiksettanne periapsiksittanne
instructive
comitative periapsiksinenne
third-person possessor
singular plural
nominative periapsiksensa periapsiksensa
accusative nom. periapsiksensa periapsiksensa
gen. periapsiksensa
genitive periapsiksensa periapsistensa
periapsiksiensa
partitive periapsistaan
periapsistansa
periapsiksiaan
periapsiksiansa
inessive periapsiksessaan
periapsiksessansa
periapsiksissaan
periapsiksissansa
elative periapsiksestaan
periapsiksestansa
periapsiksistaan
periapsiksistansa
illative periapsikseensa periapsiksiinsa
adessive periapsiksellaan
periapsiksellansa
periapsiksillaan
periapsiksillansa
ablative periapsikseltaan
periapsikseltansa
periapsiksiltaan
periapsiksiltansa
allative periapsikselleen
periapsiksellensa
periapsiksilleen
periapsiksillensa
essive periapsiksenaan
periapsiksenansa
periapsiksinaan
periapsiksinansa
translative periapsiksekseen
periapsikseksensa
periapsiksikseen
periapsiksiksensa
abessive periapsiksettaan
periapsiksettansa
periapsiksittaan
periapsiksittansa
instructive
comitative periapsiksineen
periapsiksinensa
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