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Is there any scientific name for "The Moon", Earth's satellite, when talking about it apart from, but in context of, other moons? Google simply states that

Earth's only natural satellite is simply called the moon because people didn't know other moons existed until Galileo Galilei discovered four moons orbiting Jupiter in 1610. Other moons in our solar system are given names so they won't be confused with each other.

It seems sort of dumb to just call the moon "The Moon" because we never had a classification for what it is/was. I'm guessing it has some sort of astronomical name. The main difference between The Sun and The Earth and their English naming conventions is that we don't call other planets "Earths" and other stars "Suns", at least not in a scientific sense; we tend to use it informally rather.

So, does The Moon have an agreed upon international astronomical name, such as Luna or something like that? And while we're at it, there must also be a name for "The Sun" (It might be Sol) and our solar system?

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    $\begingroup$ It should be noted that, while popular in science fiction, "Luna" and "Sol" are never used in scientific or engineering literature. $\endgroup$ – pericynthion Jan 7 '15 at 20:17
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    $\begingroup$ It's just the other way round: The real, scientific name for the Moon is "Moon", and we just called every else moon-like space thing a "moon". If the Moon was named Bob, we would call natural satellites of other planets just bob: "Mars has two bobs: Phobos and Daimos." $\endgroup$ – Nova Jan 8 '15 at 3:41
  • $\begingroup$ While 'Sol' isn't used scientifically, 'sol' is. Earth is Moon's sol. For that antenna that orbits the ISS, the ISS is the sol. $\endgroup$ – SF. Nov 14 '15 at 9:57
  • $\begingroup$ @SF. Really? So what is gravitationally often called the primary can be replaced with the sol? I never read that before. Do I maybe misinterpret you, is it a historical use? And OT, what antenna is orbiting the ISS? $\endgroup$ – LocalFluff Nov 14 '15 at 11:00
  • $\begingroup$ @LocalFluff: I think there are some technical differences between "the primary" and "the sol", but I just semi-commonly heard it used in this context, I don't have a solid source. As for the antenna (antenna cover actually), ask TidalWave. :) astronomy.stackexchange.com/questions/856/do-moons-have-moons third comment under the question. $\endgroup$ – SF. Nov 14 '15 at 12:01
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It has many names, depends on who you ask. In English, one name for our moon is simply the Moon. Notice the article the and the capitalization making it a proper noun. This is similar in convention as the Galaxy for our own galaxy that is otherwise also known as the Milky Way. But the word galaxy actually already implies something related to milk in Greek anyway (galakt / γάλακτ = milk), so some linguistic purist frown upon the use the Milky Way galaxy as redundant.

Another name for our moon could be Luna by the ancient Roman deity that is, according to ancient beliefs, embodiment of the Moon. Roman / Latin names for celestial bodies (and sometimes their adjectives) are frequently used. In fact, we all know e.g. the planets Mars, Neptune, Venus,... by their Latin names for a god of war, god of fresh waters and the sea, and goddess of love, respectively, and less frequently use their Greek equivalents Ares, Poseidon, and Aphrodite.

And the Moon / Luna is known by many other names in other cultures. For example, in Greek mythology, it would be Selene, goddess of the Moon, or rarer, Cynthia or even Artemis, both the names of the Greek goddess of the hunt, forests and hills, the Moon, and archery. Obviously, this implies another name for the Moon - Diana, the Roman goddess of the hunt, the moon and birthing. And, say, Chinese equivalent would be Chang'e, their mythological goddess of the Moon (relevant to space exploration since the China National Space Administration chose this name for their lunar exploration program, and you might have heard of some of the Chang'e lunar orbiters and landers, e.g. the Chang'e 3 that delivered a small rover named Yutu, in English Jade rabbit, to the Moon). The list could go on, as evidenced for example by this Wikipedia's list of lunar deities.

So, when it comes to terminology and naming conventions (nomenclature), you should never neglect to mention what language, culture and use you're interested in. I know you did, I'm just trying to additionally emphasize that it makes a difference. But, to cut the long story short and answer your question more directly:

Does The Moon have an agreed upon international astronomical name?

Yes. The Moon. And this is the English language naming convention recommended by the International Astronomical Union (IAU):

The IAU formally recommends that the initial letters of the names of individual astronomical objects should be printed as capitals; e.g., Earth, Sun, Moon, etc. "The Earth's equator" and "Earth is a planet in the Solar System" are examples of correct spelling according to these rules.


Additionally, if I may, what you posit in the penultimate paragraph of your question seems somewhat flawed. There is a distinction between a sun and the Sun in that while they both suggest a star that is a parent to planets, i.e. a planetary system and not merely a star, the former form is both frequently used (saying, e.g., "This planet has two suns because it orbits a binary star." would be perfectly acceptable, why not?) as well as both being distinct enough with the use of articles a or the, so they cannot be ambiguous with proper use.

If it helps make a difference, here's a quote from Curious About Astronomy post on What are the names of the earth, moon, sun, and solar system?:

The name of our planet is the Earth. The name of our moon is the Moon. The name of our solar system is the Solar System.

Notice that I capitalize them, because when used as names, they are proper nouns. This also helps us distinguish between the planet Earth and earth (meaning soil), between the Earth's Moon and moon (meaning the natural satellite of a planet), and between our Solar System and any other solar systems (since any system containing a star and a planet or a planet-forming disk can be called a solar system.)

The Wikipedia page you quote seems only partially correct and neglects to mention capitalization of proper nouns. Which is somewhat amusing considering its own page on proper nouns clearly stating:

In English and many other languages, proper names and words derived from them are associated with capitalization;

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    $\begingroup$ Well, that's less than satisfying. It makes sense, since we aren't traveling between planets and moons too frequently, nor are we living anywhere else. Perhaps in the future, those living on Mars may have a name for the Earth's moon that is a bit more specific. Very thorough though, thank you $\endgroup$ – Premier Bromanov Jan 7 '15 at 21:22
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    $\begingroup$ Interesting that "it orbits a binary star" and not "it orbits two binary stars" implying "star" to mean both a single star and a group of stars. I suppose it's a contraction of "a binary star system". $\endgroup$ – Schwern Jan 7 '15 at 23:25
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    $\begingroup$ @Schwern It is possible for a planet to orbit a single star of a binary star system. Say, it could be co-orbital with the second star, not ever really orbiting it, like for example Jupiter Trojans. I actually wrote it with "system" at first, but later decided it might be more interesting if I throw a curveball instead. Nicely caught! :) $\endgroup$ – TildalWave Jan 8 '15 at 1:31
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    $\begingroup$ @TildalWave: English of course is anything Humpty Dumpty says it is. Just for an example, the Cambridge dictionary online lists "France" but not "Luna", suggesting (a) it does consider some English proper nouns to be worth including; (b) it doesn't consider "Luna" to be one of them :-) Of course you're free to hold a different opinion from any given lexicographer since English dictionaries aren't prescriptive. $\endgroup$ – Steve Jessop Jan 8 '15 at 13:58
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    $\begingroup$ @TildalWave: yes, I'm not sure how dictionaries handle poetical/literary use of proper nouns. The same source doesn't list "Albion", but to say "Albion is not a name for England or Britain in English" certainly sounds false or close to it! I'd guess that Luna in English is more likely to mean the goddess than the lump of rock, but this particular dictionary just isn't willing to help us out as to what (if anything) it's commonly used to mean. $\endgroup$ – Steve Jessop Jan 8 '15 at 14:04
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Because the moon was so well known before international agreement on astronomical naming was a thing, different languages have different words for it. In English it's "the Moon"; in the Romance languages it's usually "Lune" or "Luna" from the Latin. The modern dominance of English and the historical dominance of Latin in scientific communities pretty much guarantees that either one is recognized, and there's no particular reason to force people to use one or the other.

Similar reasoning applies to "Sun" versus "Sol".

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  • $\begingroup$ Definitely I know no language that would use name of the Moon based on English. In Russian it is for instance, "Luna" (with the last syllable stressed), and the word for crescent and a month is "meseats" which is a distant cognate of "Moon" and "month". $\endgroup$ – Anixx Jan 10 '15 at 2:54
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In most languages, including English, before Galileo, Kepler and Newton, there was only one thing called Sun and just one thing called Moon. After Galileo and Kepler, for some time, there was only one thing called Solar System.

Then Galileo (and/or Simon Marius) discovered Jupiter's satellites. They are things related to Jupiter the same as The Moon is related to Earth. So, each one of them is like a Moon, but orbiting Jupiter instead of Earth.

Quickly, saying something like that "Io is like the Moon, but orbiting Jupiter", was reduced to the similar, but quite different "Io is one of Jupiter's moons". This means that the noun moon had its meaning changed. It used to denote solely to Earth's Moon before, and then it started to denote a satellite of a planet.

The same change of meaning happened to the noun sun also. And the same for solar system.

To disambiguate that in a pedantic manner, you should use the noun satellite or natural satellite instead of the noun moon to refer to unnamed, unspecified, generic or collective entities orbiting planets, including Earth's Moon itself, reserving the word Moon just to Earth's natural satellite. The same for star and Sun and for planetary system and Solar System. This also returns the terms Moon, Sun and Solar System to their original meanings.

However, even if you start to disambiguate the terms in a pedantic manner, returning to the original meaning, don't expect that other people would follow you. Calling Io, Europa and Titan as moons is easy and common, even if it is in truth a potentially confusing and possibly wrong name-bending and using the term satellites would be the correct.

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    $\begingroup$ Well in Ruussian calling satellites of Jupiter "moons" (using the same word as for the Moon) can only be poetic. The word used to describe these bodies is an analog of Enlish "satellite". $\endgroup$ – Anixx Jan 10 '15 at 2:56
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In English, the name of the Sun is Sun, and the name of the Moon is Moon.

Your question stems from using the word moons but not earths or suns. This is really a question of etymology, and to understand how we got to this point you have to put yourself in the perspective of the ancients.

To begin with, you point out that planet and star are generic names for the kinds of objects that the Earth and the Sun are. Not using Earth or Sun for the classes of objects is quite understandable, since there was nothing to indicate that the Earth and Sun were instances of these types. So a star (to use the word how it has eventually evolved in modern English) was something entirely different from the Sun and the Moon, and a planet was just a special kind of star: the word is derived from the Greek word meaning "wander", since these stars moved through the sky relative to the other stars.

The Sun and the Moon were not members of a class of objects; they were two objects with names, and if there was anything else like them out there, we didn't know about it. Their names express the role they played in human activity. Sun (along with its cognates throughout the Indo-European languages, including Sonne, zon, sol, soleil, etc.) is derived from a word meaning "shine". The Sun is that bright thing that shines, lighting up our world. Moon is derived from the same root as month, ultimately deriving from a word meaning "measure". The Moon was (and sometimes still is!) how people measured time, and a major unit of time is how long it takes for one cycle through its phases.


Nowadays we know that the Sun is the closest example of the stars we see. But we already had the word star, so we just kept using that.

Nowadays we know that there are other objects orbiting stars like Earth does. But we already had the word planet, so we just kept using that.

And now we've learned that other planets can have objects orbiting them like our Moon does us! But this is brand-new; no ancient had any idea about this moon-planet relationship. So with no other word to turn to, we just repurposed Moon as a common noun meaning "Moon-like object". (NB: this repurposing came at approximately the same time as extending the meaning of satellite to refer to these celestial bodies. But satellite has taken on a more general meaning.)

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    $\begingroup$ I thought it's either "the Sun" or "Sol" - but not "Sun". I don't see "Sun is rising." or "Point it at Sun." without an editor fixing it by adding "the". If you look at the Wikipedia article you have linked to, The first three paragraphs all begin with "The Sun...". Likewise "The Moon..." in the first three paragraphs of that article. Whereas in the article for Jupiter The first three paragraphs all begin with "Jupiter..." $\endgroup$ – uhoh May 20 '16 at 15:26
  • $\begingroup$ but not earths or suns Actually, we have been using these words for centuries $\endgroup$ – Jan Doggen Jun 17 '16 at 13:42
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Supplemental information (NASA sez):

I just happened to have run across this, and remembered your question. In a database that contains A LOT of moons (in the solar system), They have added "Luna" for potential disambiguation - just to be sure I think, since they have dropped the pronoun "The" here.

From JPL Horizons database web interface at http://ssd.jpl.nasa.gov/horizons.cgi:

enter image description here

enter image description here

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  • $\begingroup$ VERY interesting! I wonder if that is NASA approved terminology, or simply ease of use design choice $\endgroup$ – Premier Bromanov Jun 17 '16 at 15:14

protected by kim holder Nov 13 '15 at 19:00

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