## Apsis |

The term **apsis** (**apsides** * apse*.

The major axes of the individual ellipses around the barycenter, respectively the contributions to the major axis of the orbital ellipses are inverse proportional to the masses of the bodies, i.e., a bigger mass implies a smaller axis/contribution. Only when one mass is sufficiently larger than the other, the individual ellipse of the smaller body around the barycenter comprises the individual ellipse of the larger body as shown in the second figure. For remarkable asymmetry, the barycenter of the two bodies may lie well within the bigger body, e.g., the Earth–Moon barycenter is about 75% of the way from Earth's center to its surface. If the smaller mass is negligible compared to the larger, then the orbital parameters are independent of the smaller mass (e.g. for satellites).

- For general orbits, the terms
**periapsis**and**apoapsis**(or**apapsis**) are used.**Pericenter**and**apocenter**are equivalent alternatives, referring explicitly to the respective points on the orbits, whereas periapsis and apoapsis may also refer to the smallest and largest distances of the orbiter and its host. - For a body orbiting the
Sun , the point of least distance is the**perihelion**(n /), and the point of greatest distance is the**aphelion**(n /).^{[2]} - The terms become
**periastron**and**apastron**when discussing orbits around other stars. - For any satellite of
Earth , including theMoon , the point of least distance is the**perigee**(iː /) and greatest distance the**apogee**, fromAncient Greek Γῆ (*Gē*), "land" or "earth". - For objects in
lunar orbit , the point of least distance is sometimes called the**pericynthion**(n /) and the greatest distance the**apocynthion**(n /).**Perilune**and**apolune**are also used.^{[3]}

In

- mathematical formulae
- terminology
- perihelion and aphelion
- see also
- references
- external links

These

- Pericenter
- Maximum speed, , at minimum (pericenter) distance, .
- Apocenter
- Minimum speed, , at maximum (apocenter) distance, .

While, in accordance with

where:

*a*is thesemi-major axis :*μ*is thestandard gravitational parameter *e*is theeccentricity , defined as

Note that for conversion from heights above the surface to distances between an orbit and its primary, the radius of the central body has to be added, and conversely.

The *a*. The *b*.

The geometric mean of the two limiting speeds is

which is the speed of a body in a circular orbit whose radius is .

Other Languages

Afrikaans: Apside

Alemannisch: Apsis (Astronomie)

العربية: قبا

asturianu: Ápside

বাংলা: অপদূরবিন্দু

беларуская: Апацэнтр і перыцэнтр

беларуская (тарашкевіца): Пэрыцэнтар і апацэнтар

भोजपुरी: एप्सिस

български: Апсида (астрономия)

català: Àpside

čeština: Apsida (astronomie)

dansk: Apsis (astronomi)

Deutsch: Apsis (Astronomie)

eesti: Apsiid (astronoomia)

español: Ápside

Esperanto: Apsido

euskara: Apside

فارسی: اوج و حضیض

français: Apside

galego: Apse

한국어: 장축단

հայերեն: Ապոկենտրոն և պերիկենտրոն

हिन्दी: मन्द

hrvatski: Apsida (astronomija)

Ido: Apsido (astronomio)

Bahasa Indonesia: Apsis

íslenska: Nándarstaða og firðstaða

italiano: Apside

עברית: אפסיד

ქართული: აპოცენტრი და პერიცენტრი

қазақша: Апоцентр және перицентр

Latina: Apsis

latviešu: Apsīda

lietuvių: Apsidė (astronomija)

magyar: Apszispont

македонски: Апсида (астрономија)

മലയാളം: അപസൗരം

मराठी: उपनाभी बिंदू

Bahasa Melayu: Apsis

Nederlands: Apofocus en perifocus

日本語: 近点・遠点

norsk: Apsis (astronomi)

norsk nynorsk: Apsis i astronomi

Plattdüütsch: Apsis (Astronomie)

polski: Apsyda (astronomia)

português: Apside

română: Apsidă

русский: Апоцентр и перицентр

Scots: Apsis

සිංහල: දුරාන්තිකය

Simple English: Apsis

slovenčina: Apsida (astronómia)

slovenščina: Apsidna točka

српски / srpski: Apsida (astronomija)

srpskohrvatski / српскохрватски: Apsida (astronomija)

suomi: Apsidi (tähtitiede)

svenska: Apsis

தமிழ்: சுற்றுப்பாதை வீச்சு

ไทย: จุดปลายระยะทางวงโคจร

Türkçe: Apsis

тыва дыл: Апогей

українська: Апсиди

Tiếng Việt: Củng điểm quỹ đạo

中文: 拱點