Apside — Wikipedia

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THE apsides (female name) are the two extreme points of the orbit of a celestial body, for which the distance to the attractive body (more exactly, in the center of mass of the two bodies) ^{[ a ]}East :

either minimal (lower apside, periapside or peripse);
either maximum (upper apside, apoapside or apoapse).

The word is more rarely used in the singular to designate one or the other of the two points.

The straight line connecting the periapsy and the apoapside of a given orbit is the line of apsids or Apsidial line . It is the main axis of the ellipse, that is to say the straight line which joins the two points furthest from its center.

In the case of a star and the main objects of the solar system, a specialized-related term can be used as indicated in the table below. The name of these smaller and greater removal points depend on the central body; They are formed by taking the Greek root of the name of this body ^{[ first ]}, which is generally the name of a god.

However, only the Périhelie and Aphélie, perigée and apogeée, periastre and apoaster couples are commonly used.

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corps central	Greek root	périapside	apoapside
Galaxy	Galaxy (< galakt- ” milk “, cf. Milky Way)	Périgalacticon	Apogalacticon
Black hole	Masasma (” black spot “)	Outdated	Daddy
Star	Astḗr (” star “)	Peiastre	Apoastre
Sun	hḗlios (” sun “)	Berihélie	Aphélie ^{[ b ]}
Mercury	Hermès (Commerce God)	Periheal	Apherme ^{[ b ]}
Venus	Cythera (Venus/Aphrodite birthplace)	Peric	Apocysers
Earth	gaia (dialectal form of bo ” earth “)	Perigee	Apogee
Moon	Sel (” moon “)	Perisèle	Aposaler
Mars	Ares (God of warlike fury)	Periana	Apoar
Jupiter	Zeus (king of the gods)	Perizen	Apple
Saturn	Cronos (King of Titans, father of the previous one)	Péron	Apocrone
Uranus	Ouranos (Heaven, father of the previous one)	Periourane	Apourane
Neptune	Poseidon (God of the sea)	Accreamer	Apoposeide
Pluton	Hades (master of hell)	Perihade	Aphade ^{[ b ]}

Terms PRILUIGIA or apolune (for the natural satellite of a moon), pear or apojove (For a Jupiter satellite) are to be avoided.

We sometimes also see the terms péricynthe or apocynthe In the case of an artificial satellite of the moon.

Table of Contents

Relative positions of the planets of the solar system [ modifier | Modifier and code ]

The two images below show the relative position of périapsides (a host) a apoapsides (in red) planets of the solar system, in our time .
The one on the left for the most interior planets, and the one on the right for the most external planets.

Position relative des périapsides (a host) a apoapsides (in red) of the most interior planets of the solar system.

Position relative des périapsides (a host) a apoapsides (in red) of the most outdoor planets of the solar system.

The following formulas make it possible to calculate the distance of each of the apsides in the center of mass, and the speed in these points:

	périapside	apoapside
distance	${displaystyle r_{mathrm {per} }=(1-e)a!,}$	${displaystyle r_{mathrm {ap} }=(1+e)a!,}$
speed	${displaystyle v_ {matrm {per}} = {sqrt {tfrac {(1+e) mu} {(1-e) a}}}}$	${Displaystyle v_ {matrm {ap}} = {sqrt {tfrac {(1-e) mu} {(1+e) a}}}}$

According to the laws of Kepler on the movement of the planets (conservation of the angular moment) and the principles of the conservation of energy, the following quantities are constant for a given orbit:

with :

${displaystyle a!,}$
${displaystyle mu !,}$
${displaystyle e!,}$

Please note: to convert the distance measured from the surfaces of objects in distance measured from the centers of gravity, you must add the radius of orbit objects; and reciprocally.

The arithmetic average of the two extreme distances is the length of the half-line

{displaystyle a!,}

$a!,$ of the orbital ellipse.
The geometric average of these same two distances is the length of the half axis

{displaystyle b!,}

$b!,$ of the elle orbital elle.

The geometric average of the two limit speeds

{displaystyle {sqrt {-2epsilon }}}

${sqrt {-2epsilon }}$ , is the speed corresponding to a kinetic energy which, to any position on the orbit, added to current kinetic energy, would allow the orbit object to escape from the attraction. The square root of the product of the two speeds is therefore the local value of the release speed.

Notes [ modifier | Modifier and code ]

↑ The center of mass (in practice the attractive body when it is much more massive than the body considered) is located at one of the two households of the orbit.
↑ ^{A B and C}Note: In terms Aphélie , apherme And aphade , the ph appears following the regular apocope of the prefix apo- before vowel, even if this vowel is sucked up (that is to say, graphically, preceded by a h ). That the p and the h belong to different morphemes does not change the pronunciation of the digger ph : word short-lived (< ep(i)-hēmeros ) is another example. That these terms are of modern training does not change anything to their purely Greek character either: as a French borrowed of Greek words existing in power, the pronunciation of the ph is the same as in any other Greek word borrowed in French. We therefore pronounce: [AFELI], [AFɛʁm] and [Afad]. Pronunciation [AP-] is hypercorrection.

References [ modifier | Modifier and code ]

external links [ modifier | Modifier and code ]

[1] The center of mass (in practice the attractive body when it is much more massive than the body considered) is located at one of the two households of the orbit.

[ap-h-3] {A B and C}Note: In terms Aphélie , apherme And aphade , the ph appears following the regular apocope of the prefix apo- before vowel, even if this vowel is sucked up (that is to say, graphically, preceded by a h ). That the p and the h belong to different morphemes does not change the pronunciation of the digger ph : word short-lived (< ep(i)-hēmeros ) is another example. That these terms are of modern training does not change anything to their purely Greek character either: as a French borrowed of Greek words existing in power, the pronunciation of the ph is the same as in any other Greek word borrowed in French. We therefore pronounce: [AFELI], [AFɛʁm] and [Afad]. Pronunciation [AP-] is hypercorrection.

Apside — Wikipedia

Relative positions of the planets of the solar system [ modifier | Modifier and code ]

Notes [ modifier | Modifier and code ]

References [ modifier | Modifier and code ]

Related articles [ modifier | Modifier and code ]

external links [ modifier | Modifier and code ]

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