In astronomy, an **apsis**, plural *apsides* (IPA: /apsɪdɪːz/) is the point of greatest or least distance of the elliptical orbit of an astronomical object from its center of attraction, which is generally the center of mass of the system. Image File history File links Orbit. ...
Image File history File links Orbit. ...
The elements of an orbit are the parameters needed to specify that orbit uniquely, given a model of two ideal masses obeying the Newtonian laws of motion and the inverse-square law of gravitational attraction. ...
A giant Hubble mosaic of the Crab Nebula, a supernova remnant. ...
For information on how to read IPA transcriptions of English words see here. ...
In astrodynamics or celestial mechanics a elliptic orbit is an orbit with the eccentricity greater than 0 and less than 1. ...
See also Lists of astronomical objects Category: ...
In physics, the center of mass of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it were concentrated. ...
The point of closest approach is called the **periapsis** or **pericentre** and the point of farthest excursion is the **apoapsis** (Greek από, *from*, which becomes απ before a vowel, and αφ before rough breathing), **apocentre** or **apapsis** (the latter term, although etymologically more correct, is much less used). A straight line drawn through the periapsis and apoapsis is the *line of apsides*. This is the major axis of the ellipse, the line through the longest part of the ellipse. The ellipse and some of its mathematical properties. ...
Related terms are used to identify the body being orbited. The most common are **perigae** and **apogae**, referring to orbits around the Earth, and **perihelion** and **aphelion**, referring to orbits around the Sun (Greek ‘ήλιος *hēlios* sun). ## Formular
There are formulae used to derive apsis and periapsis: In mathematics and in the sciences, a formula (plural: formulae, formulÃ¦ or formulas) is a concise way of expressing information symbolically (as in a mathematical or chemical formula), or a general relatx E=mcÂ² (see special relativity). ...
- Periapsis: maximum speed at minimum distance (periapsis distance)
- Apoapsis: minimum speed at maximum distance (apoapsis distance)
where one easily verifies (each the same for both points, like they are for the whole orbit, in accordance with Kepler's laws of planetary motion (conservation of angular momentum) and the conservation of energy) Johannes Keplers primary contributions to astronomy/astrophysics were his three laws of planetary motion. ...
This gyroscope remains upright while spinning due to its angular momentum. ...
where: Properties: The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae. ...
In astrodynamics, under standard assumptions any orbit must be of conic section shape. ...
In astrodynamics specific relative angular momentum () of orbiting body () relative to central body () is the relative angular momentum of per unit mass. ...
In astrodynamics the specific orbital energy (or vis-viva energy) of an orbiting body traveling through space under standard assumptions is the sum of its potential energy () and kinetic energy () per unit mass. ...
In astrodynamics, the standard gravitational parameter () of a celestial body is the product of the gravitational constant () and the mass : The units of the standard gravitational parameter are km3s-2 Small body orbiting a central body Under standard assumptions in astrodynamics we have: where: is the mass of the orbiting...
Note that for conversion from heights above the surface to distances, the radius of the central body has to be added, and conversely. The arithmetic mean of the two distances is the semi-major axis . The geometric mean of the two distances is the semi-minor axis . In mathematics and statistics, the arithmetic mean (or simply the mean) of a list of numbers is the sum of all the members of the list divided by the number of items in the list. ...
The geometric mean of a set of positive data is defined as the nth root of the product of all the members of the set, where n is the number of members. ...
In geometry, the semi-minor axis (also semiminor axis) applies to ellipses and hyperbolas. ...
The geometric mean of the two speeds is , the speed corresponding to a kinetic energy which, at any position of the orbit, added to the existing kinetic energy, would allow the orbiting body to escape (the square root of the sum of the squares of the two speeds is the local escape velocity).
## Terminology The words "pericentre" and "apocentre" are occasionally seen, although periapsis/apoapsis are preferred in technical usage. Various related terms are used for other celestial objects. The '-gee', '-helion' and '-astron' and '-galacticon' forms are frequently used in the astronomical literature, while the other listed forms are occasionally used, although '-saturnium' has very rarely been used in the last 50 years. The '-gee' form is commonly (although incorrectly) used as a generic 'closest approach to planet' term instead of specifically applying to the Earth. The term *peri/apomelasma* (from the Greek root) was used by Geoffrey A. Landis in 1998 before *peri/aponigricon* (from the Latin) appeared in the scientific literature in 2002. See lists of astronomical objects for a list of the various lists of astronomical objects in Wikipedia. ...
Geoffrey A. Landis emerged in the late 1980s as one of the foremost scientist-writers in the science fiction genre. ...
1998 (MCMXCVIII) was a common year starting on Thursday of the Gregorian calendar, and was designated the International Year of the Ocean. ...
For album titles with the same name, see 2002 (album). ...
Body | Closest approach | Farthest approach | Galaxy | Perigalacticon | Apogalacticon | Star | Periastron | Apastron | Black hole | Perimelasma/Perinigricon | Apomelasma/Aponigricon | Sun | Perihelion | Aphelion^{[1]} | Mercury | Perihermion | Apohermion | Venus | Pericytherion/Pericytherean/Perikrition | Apocytherion/Apocytherean/Apokrition | Earth | Perigae | Apogae | Moon | Periselene/Pericynthion/Perilune | Aposelene/Apocynthion/Apolune | Mars | Periareion | Apoareion | Jupiter | Perizene/Perijove | Apozene/Apojove | Saturn | Perikrone/Perisaturnium | Apokrone/Aposaturnium | Uranus | Periuranion | Apouranion | Neptune | Periposeidion | Apoposedion | Pluto | Perihadion | Apohadion | Since "peri" and "apo" are Greek, it is considered by some purists^{[2]} more correct to use the Greek form for the body, giving forms such as '-zene' for Jupiter and '-krone' for Saturn. The daunting prospect of having to maintain a different word for every orbitable body in the solar system (and beyond) is the main reason why the generic '-apsis' has become the almost universal norm. NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 17,000 parsecs in diameter and approximately 20 million parsecs distant. ...
This article is about the astronomical object. ...
A black hole is an object predicted by general relativity,[1] with a gravitational field so powerful that even electromagnetic radiation (such as light) cannot escape its pull. ...
The Sun is the star at the center of the Solar System. ...
Note: This article contains special characters. ...
Adjectives: Venusian or (rarely) Cytherean Atmosphere Surface pressure: 9. ...
Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ...
Apparent magnitude: up to -12. ...
Note: This article contains special characters. ...
Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ...
Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ...
Adjectives: Uranian Atmosphere Surface pressure: 120 kPa (at the cloud level) Composition: 83% Hydrogen 15% Helium 1. ...
Note: This article contains special characters. ...
Adjectives: Plutonian Atmosphere Surface pressure: 0. ...
- In the Moon's case, in practice all three forms are used, albeit very infrequently. The '-cynthion' form is, according to some, reserved for artificial bodies, whilst others reserve '-lune' for an object launched
*from* the Moon and '-cynthion' for an object launched from elsewhere. The '-cynthion' form was the version used in the Apollo Project, following a NASA decision in 1964. - For Venus, the form '-cytherion' is derived from the commonly used adjective 'cytherean'; the alternate form '-krition' (from Kritias, an older name for Aphrodite) has also been suggested.
- For Jupiter, the '-jove' form is occasionally used by astronomers whilst the '-zene' form is never used, like the other pure Greek forms ('-areion' (Mars), '-hermion' (Mercury), '-krone' (Saturn), '-uranion' (Uranus), '-poseidion' (Neptune) and '-hadion' (Pluto)).
Description Role: Earth and Lunar Orbit Crew: 3; CDR, CM pilot, LM pilot Dimensions Height: 36. ...
The Birth of Venus, (detail) by Sandro Botticelli, 1485 Aphrodite (Greek: á¼ˆÏ†ÏÎ¿Î´Î¯Ï„Î·, pronounced in English as and in Ancient Greek as ) was the Greek goddess of love, lust, beauty, and sexuality. ...
## Earth's perihelion and aphelion The Earth is closest to the Sun in early January and furthest in early July. The relation between perihelion, aphelion and the Earth's seasons changes over a 25,765 year cycle. This precession of the equinoxes contributes to periodic climate change, Precession of the equinoxes refers to the precession of the Earths axis of rotation. ...
It has been suggested that Global warming in popular culture be merged into this article or section. ...
The day and hour of these events for the next few years are:[1] Year | Perihelion | Aphelion | 2007 | Jan 3 20 Z | July 7 00Z | 2008 | Jan 3 00Z | July 4 08Z | 2009 | Jan 4 15Z | July 4 02Z | 2010 | Jan 3 00Z | July 6 11Z | 2011 | Jan 3 19Z | July 4 15Z | 2012 | Jan 5 00Z | July 5 03Z | 2013 | Jan 2 05Z | July 5 15Z | 2014 | Jan 4 12Z | July 4 00Z | 2015 | Jan 4 07Z | July 6 19Z | 2016 | Jan 2 23Z | July 4 16Z | UTC redirects here. ...
## See also The eccentric anomaly is the angle between the direction of periapsis and the current position of an object on its orbit, projected onto the ellipses circumscribing circle perpendicularly to the major axis, measured at the centre of the ellipse. ...
Two bodies with similar mass orbiting around a common barycenter with elliptic orbits. ...
Perigee is the point at which an object in orbit around the Earth makes its closest approach to the Earth. ...
## Notes and references **^** Properly pronounced 'affelion' because the Greek is αφήλιον, although the hypercorrection 'ap-helion' is commonly heard. **^** Apsis. *Glossary of Terms*. National Solar Observatory (February 21, 2005). Retrieved on 2006-09-30. Hypercorrection comprises two linguistic phenomena: elaborate, prescriptively based correction of common usage, often introduced in an attempt to avoid vulgarity or informality, that results in wording commonly considered clumsier than the usual, colloquial usage. ...
For the Manfred Mann album, see 2006 (album). ...
September 30 is the 273rd day of the year (274th in leap years) in the Gregorian calendar. ...
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