When was the Sun renamed to Sol in the Star Trek universe and why? We've been using "The Sun" name for centuries and I can't find any reasonable reason for renaming it to "Sol" or anything else.

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    It is common in science fiction to name our sun sol (and by the way the earth "terra"). Sun is a general term - for suns. Before space travel "sun" is pretty unambigous. But with space travel not. So it makes sense to give it a name and to use the word sun as a generic term.
    – Hothie
    Jun 10, 2015 at 11:52
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    About as long as Earth has been Terra, I'd imagine. Jun 10, 2015 at 14:13
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    The use of Sol apparently was first noted in 1450, apparently based off roman latin.. earthsky.org/space/what-is-the-suns-name here's a cool link :-) Jun 10, 2015 at 14:41
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    @Hothie Yep. See the Science Fiction Citations site for the history of the usage of the terms Luna, Sol, Sol III, Tellus, and Terra in science fiction.
    – user14111
    Jun 10, 2015 at 18:13
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    See also scifi.stackexchange.com/q/152699/4918 "Where did using “Luna” as the future name for the moon come from?" and scifi.stackexchange.com/q/116820/4918 "What is the origin of the word “terrans” when referring to humanoids and other earth-related things?"
    – b_jonas
    Feb 16, 2017 at 11:12

6 Answers 6


Sol is the name of our Star, the Sun is a big star.

If you ask a room full of aliens what they think of the sun, you will get a different answer from each one, depending on the star that their home planet orbits.

If you ask them about Sol, you are asking specifically about the star that the Earth orbits, which you can also refer to as Sol III to get inline with most designations they give to planets that are encountered.

  • 51
    The sun is not a particularly big star.
    – OrangeDog
    Jun 10, 2015 at 12:45
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    @OrangeDog: bigger than average, although what the average is depends of course where you choose to draw the line how small something can be and is still a star. Jun 10, 2015 at 12:49
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    @DrRDizzle is right, this answer is wrong. Our solar system is named Solar System, our sun is named the Sun and our moon is named the Moon. They're written as proper nouns to make a clarification. "Sol" surely is used widely for our Solar System, but it's not the official name the IAU has set. Reference: curious.astro.cornell.edu/our-solar-system/159-our-solar-system/…
    – Trollwut
    Jun 10, 2015 at 13:15
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    The Sun is in the 90th percentile of luminosity or so. Hardly average. There are much brighter stars, but they're rare. Just do a count of stars in a nearby star catalog (out to 25 parsecs). Also, en.wikipedia.org/wiki/Stellar_classification Jun 13, 2015 at 16:32
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    This is because the Latin word for the same thing is likely less ambiguous than the English one to those aliens? Jun 13, 2015 at 19:19

First of all, using "Sol" is basically like saying "Sun" - it's the Roman name for the Sun god and for the sun itself.

Secondly, it's a common name for our sun (and by association, our solar system), not only in Star Trek but in science fiction in general. Asimov used it as far back as the original Foundation in 1951, Heinlein used it in 1939's Misfit (thanks to Ross Presser for that catch), and it's been used by dozens of other works of fiction, before or since.

Based on that, I wouldn't be surprised if you won't find any in-universe explanations, for the same reason you won't find an in-universe explanation for why they call starships, starships: it's an established-enough science fiction term that doesn't need specific in-universe explanation.

The reason for its use over the English sun (much like earth) is that sun a universal, singular word that carries the assumption that there is just the one Sun. So the English usage for sun is both "The star in the center of a solar system" and "This particular star, the one our planet revolves around, in the uncharted backwaters of the unfashionable end of the western spiral arm of the Galaxy". To prevent this ambiguity and allow English-speaking colonists in other solar systems to use sun for their sun, the Latin Sol is used for this sun.

If more science fiction novels were written in Latin, I'm guessing a different word would have been used. :)

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    Note "our solar system", not "our sun's system" ;-) I wonder whether the English-speaking colonists should worry about that, and call them "stellar systems" or something to avoid earth-centrism. Jun 10, 2015 at 12:46
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    @SteveJessop What?! They don't refer to the sunar system where you are from? Weird. ;)
    – Lexible
    Jun 10, 2015 at 14:50
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    @SteveJessop There is only one solar system. It is ours.
    – corsiKa
    Jun 10, 2015 at 16:07
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    Good answer. I don't have any proof but I'd make an educated guess that you're right that "Sol" is one of the conventions that Star Trek inherited from print SF. (Many of the writers of TOS episodes came from the '60s SF community, not just the famous ones like Harlan Ellison.) The Latinate names for our sun, Earth, and moon are ubiquitous in SF by Golden Age writers, not just in Asimov--the first example that comes to my mind is Heinlein's The Moon Is A Harsh Mistress, which is written in the first person and almost exclusively uses the proper names "Sol," "Terra," and "Luna." Jun 10, 2015 at 16:38
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    @AvnerShahar-Kashtan: Heinlein used it in 1939 in "Misfit". The Navigator slipped a notebook out of his tunic. "Three hundred fifty-eight miles per second; course is right ascension fifteen hours, eight minutes, twenty-seven seconds, declination minus seven degrees, three minutes; solar distance one hundred and ninety-two million four hundred eighty thousand miles. Our radial position is twelve degrees above course, and almost dead on course in R.A. Do you want Sol's co-ordinates?" Jun 11, 2015 at 14:50

Risking the wrath that an out-of-universe answer will attract, the question is a bit flawed. Here's why:

If your argument is that the name "Sun" predates the word "Sol", you are mistaken. The Romans called the sun "Sol". So do many people even today.

  • Spanish: Sol

  • Portuguese: Sol

  • French: Soleil

  • Italian: Sole

  • Swedish: Sol

And so on. In addition to this, many sun gods are named Sol, or some variation thereof - the Romans called their sun god "Sol", and later "Sol Invictus"; Sol was also the name of sun gods in Norse and Germanic mythology, among others.

Even in English, we refer to the group of planets in which we live, and the star which they orbit, The Solar System. More loosely, any arrangement of a star orbited by planets is called a solar system (note the difference in capitalization- it is subtle but important).

"The Sun" (capitalized) refers to our star, while "the sun" can refer to any star orbited by planets. But no one, as far as I know, refers to other stars as Sol, or any variation thereof, aside from the aforementioned exception regarding "solar systems". We do name other stars, regardless of whether or not they are orbited by planets; sometimes we give it an actual name (Polaris, Betelgeuse, Sirius, etc); sometimes we give it a more technical title, usually a combination of letters and numbers; sometimes we use a name plus a number (e.g., Rigel 7).

However, this does not mean that Sol is the official name of our sun; nor is "the sun", although "The Sun" (capitalized) always refers to our star. In fact, our star has no proper name in English:

Bottom line: The International Astronomical Union hasn’t sanctioned an official name for our sun, and our sun doesn’t have a generally accepted and unique proper name in the English language. But, in history and in other languages, the sun does have proper names.

Some call it The Sun, some call it Sol, some used to call it Helios, or Ra, or any number of other names. It does, on the other hand, have an official symbol:

enter image description here

To get back to the specific issue of why the word Sol is used in Star Trek, the answer is fairly easy to see, in light of the above information: if you travel across the galaxy/universe on a regular basis, using the word "Sol" avoids potential confusion stemming from the fact that any star orbited by planets is a sun. I would assume that the folks in the Federation decided to call our sun "Sol" to distinguish it from every other star orbited by planets, of which there are billions in our galaxy alone.

It is easy to understand this reasoning if you imagine a situation where we referred to all planets as earths. How would anyone know which earth the captain was trying to get to if every planet was called earth?

The same concept is at work in our use of the word "moon" - we have named every moon in our solar system except our own moon. Just as we refer to our own sun as "The Sun" (capitalized) to avoid confusion, we refer to our moon as "The Moon" (capitalized) to avoid confusion. But every other moon in our solar system has a specific name - Europa, Titan, Minas, Io, etc. Again, our moon doesn't have a proper, official name, at least in English, but it does have an official symbol: a crescent, which can face either direction: ☾ or ☽

So, in short, chances are the people in Star Trek simply want to avoid confusion, so they decided to call our star "Sol", to differentiate it from every other sun.

  • For reference, here is chart of the official symbols for each of the major bodies of our solar system.
    – Wad Cheber
    Jun 11, 2015 at 1:43
  • "But no one, as far as I know, refers to other stars as Sol" Except the Spaniards, the Portuguese and the Swedes.
    – Taemyr
    Jun 11, 2015 at 8:30
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    In many SF works, our moon is unambiguously called "Luna".
    – Agent_L
    Jun 11, 2015 at 14:34
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    @Taemyr, while it is possible to refer to other stars as "sol" (no capitalization), we generally just call them stars ("stjärnor") in Swedish. Sol/sol almost always, and unambiguously, refers to the star in the center of our solar system.
    – imolit
    Jun 15, 2015 at 13:19
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    It's a Germanic language, far away from the borders of Rome at its heyday. So you are probably right. We do have a score of loanwords from Latin and French, but I think they were introduced during the Age of Enlightenment, mostly. Why Scandinavia says "sol", while it's "sun" in English (and Old Norse) and "Sonne" in German I cannot say.
    – imolit
    Jun 17, 2015 at 0:51

I suggest that the usage depends on the point of reference.

  1. When referring to the object as a star without reference to a planet, it's called "Sol".
  2. When referring to it from one of the orbiting planets, a star is also called the planet's "sun".

Evidence for #1: a star chart from the Wrath of Khan shows the name "Sol". Since star charts show a broad view of space, specific names are needed to disambiguate.

Evidence for #2: on the TNG episode Hide and Q, Riker makes note of the "dual suns" of Q's "fake" planet. It seems to me that it was clearer of him to say "dual suns" as opposed to "dual stars" because he was speaking as one viewing the stars from the planet.

It's possible that those from earth (or other planets in the Sol system) may refer to Sol as "the sun", purely out of tradition.


Historically, the Sun was once called Sol by a variety of non-scientific groups, mythologies and languages. This was good enough for NON-scientists. When scientists got involved, they decided the primacy of our SUN meant it didn't need a name. It was THE SUN, the only one we had. Just like our MOON is THE MOON, the only one we will ever have.

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.

This is the English language usage approved by the International Astronomical Union, the body in charge of naming celestial objects. It may seem odd that these important objects don't have names, but if you think about it, it just reinforces their importance. For example, the Moon is the Moon, not just any moon. It requires no other name, because it's the most important moon!

You may read or hear people using Luna for the Moon, or Terra or Gaia for the Earth, or Sol for the Sun, but in English-speaking countries, these are poetic terms, often seen in science fiction stories, but not used by astronomers in scientific writing. In some countries where Romance languages are spoken, these terms are the official names. (REF: Ask an Astronomer)

The reason it's called Sol in science fiction is because:

  • Science fiction extrapolates the idea there will be life on other planets.

  • That if said life is intelligent it will either name our star FOR us or expect us to grow up and name it ourselves.

  • In most science fiction, the word for our sun became its legendary name of Sol. Earth became Terra or Earth, and the Moon became Luna to designate it different from any other moon in any other star system.

  • This is a genre convention, nothing more. Star Trek took said genre convention and applied it to their writing.


  • Memory Alpha says the star in the solar system where Earth was found was classified as a type-G yellow dwarf star, Sol (also known as The Sun) was the primary for the Sol system. This system was located within a stellar cluster in Sector 001 (or Sol sector), a region of space in the Alpha Quadrant.

  • Given that aliens arriving in our star system would want to give our star a designation WE would prefer, it is likely that, even though the IAU would call our sun, The Sun, when we were the only game in town, once we had confirmation of other life in the Universe, and there were officially OTHER suns, we would have to give our sun a NAME.

What better name than the Latin word which has translated directly into half a dozen other languages as Sol?

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    "The only one we will ever have" UNLESS we find a black monolith on the moon which directs us to another one near Jupiter which eventually causes an endless number of other monoliths to appear within the Red Spot, quickly replacing Jupiter itself, and turning Jupiter into a second sun within our solar system, a la 2010: The Year We Make Contact.
    – Wad Cheber
    Jun 11, 2015 at 1:16
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    @WadCheber Was I the only one who was so disappointed when 2010 came and went without Jupiter turning into a new star? ;-)
    – user11521
    Jun 11, 2015 at 17:14
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    Because we would never use the words "sunar" or "moonar". We use "solar" and "lunar". The fact that there are dozens of moons in the solar system and yet only one of them is called "the moon" is about as unscientific as "if you can dodge a wrench you can dodge a ball".
    – corsiKa
    Jun 12, 2015 at 15:04
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    @WadCheber: I never watched either of the movies, but I read all 4 books a while back. Jun 13, 2015 at 11:18
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    @corsika I've seen multiple peer reviewed papers showing that if you can dodge a wrench you can dodge a ball is true for most instances of wrench and ball.
    – user16696
    Jun 15, 2015 at 4:09

Sol is Latin which means sun. Many languages like Spanish Sol means sun. It also seems more exotic to use it in the English language.

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