DavidACaruso wrote:Re: APOD, March 16, 2009
Why call Deimos a moon? We usually think of moons as something spherical, and probably relatively significant in size. Common sense (which may be incorrect) tells us Deimos is an asteroid caught in Mars orbit. Following the logic of categorizing Deimos as a moon, then perhaps categorize even the smallest rocks that fit in your hand that orbit a planet as "moons". Deimos even looks like your stereotypical asteroid.
You may call them natural satellites if you prefer.
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Satellite, n. [F., fr. L.
Stelles, -itis, an attendant.]
1. An attendant attached to a prince or other powerful person; hence, an obsequious dependent.
2. (Astron.) A secondary planet which revolves about another planet; as, the moon is a satellite of the earth.
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"My little love apprencisses, my dears, the
estelles, van Nessies" - Finnegans Wake page
365.28
.....................................................
"Stella" (Esther) Johnson (March 18, 1681 – January 28, 1728) was the English friend of Jonathan Swift. A curious collection of her witticisms was published by Swift under the titles of "Bon Mots de Stella" as an appendix to some editions of Gulliver's Travels.
.....................................................
"Vanessa" (Esther) Vanhomrigh(c. 1688 – 2 June 1723), an Irish woman of Dutch descent, was a longterm lover and correspondent of Jonathan Swift. Swift's letters to her were published after her death. She was fictionalized as "Vanessa" in Swift's poem Cadenus and Vanessa (1713).
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http://en.wikipedia.org/wiki/Natural_satellite wrote:
<<A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. The first known natural satellite was the Moon (luna in Latin). Until the discovery of the Galilean satellites in 1610, however, there was no opportunity for referring to such objects as a class. Galileo chose to refer to his discoveries as Planetæ ("planets"), but later discoverers chose other terms to distinguish them from the objects they orbited.
Christiaan Huygens, the discoverer of Titan, was the first to use the term moon for such objects, calling Titan Luna Saturni or Luna Saturnia – "Saturn's moon" or "The Saturnian moon", because it stood in the same relation to Saturn as the Moon did to the Earth.
As additional moons of Saturn were discovered, however, this term was abandoned. Giovanni Domenico Cassini sometimes referred to his discoveries as planètes in French, but more often as satellites, using a term derived from the Latin satelles, meaning "guard", "attendant", or "companion", because the satellites accompanied their primary planet in their journey through the heavens.
The term satellite thus became the normal one for referring to an object orbiting a planet, as it avoided the ambiguity of "moon". In 1957, however, the launching of the artificial object Sputnik created a need for new terminology. The terms man-made satellite or artificial moon were very quickly abandoned in favor of the simpler satellite, and as a consequence, the term has come to be linked primarily with artificial objects flown in space – including, sometimes, even those which are not in orbit around a planet.
As a consequence of this shift in meaning, the term moon, which had continued to be used in a generic sense in works of popular science and in fiction, has regained respectability and is now used interchangeably with satellite, even in scientific articles. When it is necessary to avoid both the ambiguity of confusion with the Earth's moon on the one hand, and artificial satellites on the other, the term natural satellite (using "natural" in a sense opposed to "artificial") is used.
There is no established lower limit on what should be considered a moon. Every body with an identified orbit, some as small as a kilometer across, has been identified as a moon, though objects a tenth that size within Saturn's rings, which have not been directly observed, have been called moonlets. Small asteroid moons, such as Dactyl, have also been called moonlets.
The upper limit is also vague. When the masses of two orbiting bodies are similar enough that one cannot be said to orbit the other, they are described as a double body rather than primary and satellite. Asteroids such as 90 Antiope are considered double asteroids, but they have not forced a clear definition as to what constitutes a moon. Some authors consider the Pluto-Charon system to be a double (dwarf) planet. The most common dividing line on what is considered a moon rests upon whether the barycentre is below the surface of the larger body, though this is somewhat arbitrary, as it relies on distance as well as relative mass.
As of September 2008, 335 bodies are formally classified as moons. They include 167 orbiting six of the eight planets, 6 orbiting three of the five dwarf planets, 104 asteroid moons, and 58 satellites of Trans-Neptunian objects, some of which will likely turn out to be dwarf planets. Some 150 additional small bodies were observed within Saturn's ring system, but they were not tracked long enough to establish orbits. Other stars and their planets are likely to have natural satellites as well, although none have been observed.>>
[quote="DavidACaruso"]Re: APOD, March 16, 2009
Why call Deimos a moon? We usually think of moons as something spherical, and probably relatively significant in size. Common sense (which may be incorrect) tells us Deimos is an asteroid caught in Mars orbit. Following the logic of categorizing Deimos as a moon, then perhaps categorize even the smallest rocks that fit in your hand that orbit a planet as "moons". Deimos even looks like your stereotypical asteroid.[/quote]
You may call them natural satellites if you prefer.
---------------------------------------------------------------
Satellite, n. [F., fr. L. [b]Stelles[/b], -itis, an attendant.]
1. An attendant attached to a prince or other powerful person; hence, an obsequious dependent.
2. (Astron.) A secondary planet which revolves about another planet; as, the moon is a satellite of the earth.
------------------------------------------------
"My little love apprencisses, my dears, the [b]estelles[/b], van Nessies" - Finnegans Wake page [b]365.28[/b]
.....................................................
[url=http://en.wikipedia.org/wiki/Esther_Johnson][b]"Stella" (Esther) Johnson[/b][/url] (March 18, 1681 – January 28, 1728) was the English friend of Jonathan Swift. A curious collection of her witticisms was published by Swift under the titles of "Bon Mots de Stella" as an appendix to some editions of Gulliver's Travels.
.....................................................
[url=http://en.wikipedia.org/wiki/Esther_Vanhomrigh][b]"Vanessa" (Esther) Vanhomrigh[/b][/url](c. 1688 – 2 June 1723), an Irish woman of Dutch descent, was a longterm lover and correspondent of Jonathan Swift. Swift's letters to her were published after her death. She was fictionalized as "Vanessa" in Swift's poem Cadenus and Vanessa (1713).
---------------------------------------------------------------
[quote=" http://en.wikipedia.org/wiki/Natural_satellite "]
<<A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. The first known natural satellite was the Moon (luna in Latin). Until the discovery of the Galilean satellites in 1610, however, there was no opportunity for referring to such objects as a class. Galileo chose to refer to his discoveries as Planetæ ("planets"), but later discoverers chose other terms to distinguish them from the objects they orbited.
Christiaan Huygens, the discoverer of Titan, was the first to use the term moon for such objects, calling Titan Luna Saturni or Luna Saturnia – "Saturn's moon" or "The Saturnian moon", because it stood in the same relation to Saturn as the Moon did to the Earth.
As additional moons of Saturn were discovered, however, this term was abandoned. Giovanni Domenico Cassini sometimes referred to his discoveries as planètes in French, but more often as satellites, using a term derived from the Latin satelles, meaning "guard", "attendant", or "companion", because the satellites accompanied their primary planet in their journey through the heavens.
The term satellite thus became the normal one for referring to an object orbiting a planet, as it avoided the ambiguity of "moon". In 1957, however, the launching of the artificial object Sputnik created a need for new terminology. The terms man-made satellite or artificial moon were very quickly abandoned in favor of the simpler satellite, and as a consequence, the term has come to be linked primarily with artificial objects flown in space – including, sometimes, even those which are not in orbit around a planet.
As a consequence of this shift in meaning, the term moon, which had continued to be used in a generic sense in works of popular science and in fiction, has regained respectability and is now used interchangeably with satellite, even in scientific articles. When it is necessary to avoid both the ambiguity of confusion with the Earth's moon on the one hand, and artificial satellites on the other, the term natural satellite (using "natural" in a sense opposed to "artificial") is used.
There is no established lower limit on what should be considered a moon. Every body with an identified orbit, some as small as a kilometer across, has been identified as a moon, though objects a tenth that size within Saturn's rings, which have not been directly observed, have been called moonlets. Small asteroid moons, such as Dactyl, have also been called moonlets.
The upper limit is also vague. When the masses of two orbiting bodies are similar enough that one cannot be said to orbit the other, they are described as a double body rather than primary and satellite. Asteroids such as 90 Antiope are considered double asteroids, but they have not forced a clear definition as to what constitutes a moon. Some authors consider the Pluto-Charon system to be a double (dwarf) planet. The most common dividing line on what is considered a moon rests upon whether the barycentre is below the surface of the larger body, though this is somewhat arbitrary, as it relies on distance as well as relative mass.
As of September 2008, 335 bodies are formally classified as moons. They include 167 orbiting six of the eight planets, 6 orbiting three of the five dwarf planets, 104 asteroid moons, and 58 satellites of Trans-Neptunian objects, some of which will likely turn out to be dwarf planets. Some 150 additional small bodies were observed within Saturn's ring system, but they were not tracked long enough to establish orbits. Other stars and their planets are likely to have natural satellites as well, although none have been observed.>>[/quote]