In Star Trek: Discovery S01E06 Lethe we see a scene in Vulcan. (We're assuming this is the Prime not the Kelvin timeline).

Vulcan is shown with moons - despite not having any.

Indeed - the following commentator writes:

Why was Vulcan shown with moons? Thought we worked that one out already?

Another observer opines:

Why did Vulcan have moons? It is WELL established that it has none (even fixed in Dir Ed of TMP).

My question is: Why was Vulcan shown with moons in Lethe?

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    Does "Because STD's production team doesn't care for the canon in the slightest?" count as an answer?
    – Theik
    Commented Oct 30, 2017 at 9:53
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    Moons come and go, see Praxis Commented Oct 30, 2017 at 10:21
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    @Theik I am never going to get past Because STDs. Thankfully now I am in a new relationship with the Orville and can practice safe viewing (i.e. free) in the privacy of my own home.
    – Peter M
    Commented Oct 30, 2017 at 11:37
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    That's no moon, it's a space station. Commented Oct 30, 2017 at 14:57
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    It seems like this has happened before (there is a TVTropes page named after it), in both cases it was claimed that what looked like a moon was actually a nearby planet, because artists have no sense of scale. Commented Oct 30, 2017 at 16:14

1 Answer 1


Let me begin by saying I haven't seen the new series so I can't speak to the general appearance of the "moons." That said, while Vulcan has no moon, there are a few comments and sources of questionable canonicity indicating that it has a "sister planet" visible in its skyline.

The Animated Series episode "Yesteryear" featured a large object visible in Vulcan's sky. When a preliminary sketch was presented to Gene Roddenberry, he wrote in block letters "NO MOON!," but the instructions were either missed or ignored.

enter image description here The Animated Series is as a rule non-canon according to Roddenberry, but he reportedly made an exception for this episode, given that Sarek later refers to its events in the TNG episode "Unification I."

SAREK: No. I never knew what Spock was doing. When he was a boy, he would disappear for days into the mountains. I asked him where he had gone, what he had done, he refused to tell me. I insisted that he tell me. He would not. I forbade him to go. He ignored me. I punished him. He endured it, silently. But always he returned to the mountains.

(Per Memory Alpha both Roddenberry and "many other production staffers" consider the episode canon, but that claim is sourced to two fanzines I don't have copies of. They're usually good about such things though, and I'll cite them throughout this answer.)

Confusing things further, Vulcan would later be shown with two things that sure as hell looked like moons in the theatrical version of The Motion Picture.

enter image description here

And then when Roddenberry wrote a novelization of the movie, it said that not only are there no other moons in Vulcan's system, there are no other planets! (Don't worry, the novelization isn't canon. I'm just including this to indicate how confused the issue was.)

The "moons" were removed from the 2001 DVD version of The Motion Picture, but there are conflicting statements about whether it was for canon reasons. Memory Alpha has two quotes from two people behind its removal.

VISUAL EFFECTS ARTIST DAVE MORTON: "Vulcan has no moon, and there were all these planets floating around it in the original release. These new Vulcan shots were done mainly to match better with the other films."

RESTORATION SUPERVISOR MICHAEL MATESSINO: "We eliminated things that you might not associate with a far-off monastic temple. We did not take our directions from a simple line of dialog. Vulcan in and of itself should be interesting without cluttering the sky. Besides, it was obvious that the sun was out in that scene. The change keeps things in the spirit of where we are going. It's not about what's up in the sky, it's about what's happening with Spock."

So now you have another headache about whether the updated DVD version ought to erase the canonicity of the original film (ask Star Wars fans whether in canon, Han shot first) and whether it should matter if the moons were erased for stylistic reasons and not to "correct" the scene.

But even before that scene, there were 20-odd years of confusion about what exactly the objects in Vulcan's sky was supposed to be. An explanation seized upon by fans was that Vulcan had a "sister planet" visible from space. Per Memory Alpha, there were two official reference books published in 1991 and 2002 that reported that information and named it "T'Khut" or "T'Kuht."

But are the reference books canon? Oh boy, I hope you're sitting down, because we just walked into another canon debate.

From Harry Lang, Senior Director of Viacom Consumer Products Interactive:

"Only the reference books (tech manual, encyclopedia, etc...) and two books by Jeri Taylor are considered canon outside the TV show and movies."

From longtime Star Trek producer Ronald D. Moore:

"We do use things like the Encyclopedia, the Chronology, the Technical Manual etc. for reference, but unless it was explicitly mentioned on screen, we won't feel bound by anything stated even in those books."

tl;dr Star Trek canon is a complete mess, and it MAY be the case that Vulcan has large objects in its skyline depending on who and what you believe determines "canon." I'll note that there other elements Star Trek: Discovery-- namely the holodeck-- that only make sense if you assume the Animated Series is canonical to some degree.

  • "given that Sarek later refers to its events in the TNG episode 'Unification I.'" - without making any statement on the intended canonicty of Yesteryear, this is a questionable claim: As cited, Sarek speaks about Spock repeatedly disappearing into the mountains without his knowledge. Yesteryear, on the other hand, has Spock endure some days in the mountains on his own as a part of a maturity test ritual. Commented Oct 30, 2017 at 22:37
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    "Vulcan would later be shown with two things that sure as hell looked like moons in the theatrical version of The Motion Picture." - although, strictly speaking, I think there is no hard evidence that the place we see is actually Vulcan rather than some other world used by Vulcans. Commented Oct 30, 2017 at 22:40
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    There's a way to resolve the conflicting claims: Vulcan itself could be a moon of a gas giant planet, with no other planets in the system.
    – Gaultheria
    Commented Oct 30, 2017 at 23:07
  • I know it's not canon, but does Spock's World mention this topic? Commented Oct 30, 2017 at 23:16
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    @MartinSchröder Per Memory Beta (basically Memory Alpha for noncanonical works), yes, T-Khut is mentioned in several novels, including Spock's World. Commented Oct 30, 2017 at 23:41

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