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Question about Jedha: Length of Day and Year?
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Sutehp
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PostPosted: Thu Jul 20, 2017 9:34 pm    Post subject: Question about Jedha: Length of Day and Year? Reply with quote

So I'm trying to find out Jedha's Length of Day in standard hours and the Length of Year in either local days or standard days. I've been trying to find anything about this in the Rogue One novelization, the Rogue One Visual Guide and Wookieepedia and came up with zip, except for a throwaway line by Cassian in the novelization about sunset being only a few hours away and how he doesn't want to be out in the open in Jedha City after dark because there's a curfew imposed by the Imperials.

According to my research, a year on a moon is measured by its orbit around its planet, rather than being measured by the time it takes the planet it orbits to complete a revolution around its sun. IOW, our Moon has a day length of one month (about 27.5 Earth days) as that is the time it takes for one day and one night to pass on the Moon (or alternatively, the time it takes for the sun to rise and set and return to the same place in the lunar sky when you began observing the sun). But because the Moon is tidally locked, the same face of the Moon is always facing the earth, so the time to complete an orbit around the Earth is also 27.5 days...which results in the lunar day being the same time as a lunar year!

Yeah, the Moon is screwy. We really like the Moon!

Anyway, I'm wondering if anyone has managed to come up with Jedha's length of day and year because I need those stats for the Womp Rat Press Rogue One fanbook I'm editing. If no official stats for those exist, then we've got a problem because I'd rather not make something up.

EDIT: As a satellite, Jedha could have a local day lasting dozens of hours.

Furthermore, does anyone know the name of the Jedha system's sun? If it's either NaJedha (the same name as the planet Jedha orbits) or Jedha (the same name as the moon Jedha), that's gonna be problematic when I need to distinguish which stellar body is orbiting which. "Jedha orbits NaJedha but NaJedha orbits NaJedha." See if you can tell which "NaJedha" is the star and which is the planet from that statement once your head stops spinning. Shocked Razz

EDIT 2: It turns out that under the Star Wars convention at least, a moon's year is indeed going to be equivalent to its parent planet's year revolving around the star, rather than the time it takes to complete a revolution around its parent planet. Thus, according to D6 stats, Yavin 4's year is equivalent to 4,818 standard days, which is 13.09 Coruscanti years, each made up of 368 standard days. Of course, when Galaxy Guide 2: Yavin and Bespin was written, everyone assumed that a standard year was the same as an Earth year (365 days), which is why Yavin 4's year in that book was listed as 13.2 standard years, not 13.09 years.
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Whill
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PostPosted: Fri Jul 21, 2017 5:10 am    Post subject: Re: Question about Jedha: Length of Day and Year? Reply with quote

Sutehp wrote:
According to my research, a year on a moon is measured by its orbit around its planet, rather than being measured by the time it takes the planet it orbits to complete a revolution around its sun. IOW, our Moon has a day length of one month (about 27.5 Earth days) as that is the time it takes for one day and one night to pass on the Moon (or alternatively, the time it takes for the sun to rise and set and return to the same place in the lunar sky when you began observing the sun). But because the Moon is tidally locked, the same face of the Moon is always facing the earth, so the time to complete an orbit around the Earth is also 27.5 days...which results in the lunar day being the same time as a lunar year!

Yes, you are correct about one technical definition of a year being the time it takes a body to orbit its primary. But Jedha is a habitable moon not much smaller than Earth, obviously with similar gravity and thus ability to hold a nitrogen-oxygen atmosphere supporting Earthlike life. For all intents and purposes in the film, Jedha is a planet and its primary is effectively just backdrop. That planet capsule data should not measure the technical definition of year for the moon with respect to its planet because that doesn't mean anything to most gamers. The convention of other planetary capsules seems to be that a moon's "year" is the time it takes the planet-moon system as a whole to orbit its star, so IOW, the moon's year is virtually identical to the planet's year. It does not seem that Jedha would be tide-locked so its own rotation should still determine its length of day (it gets most of its light from the system's star not the planet it orbits).

Something I never see addressed in Star Wars is that all these near-Earth-sized moons orbit gas giants and thus could have orbits that cast them into shadow of their primary for standard hours to standard years worth of time, technically long planetary eclipses blocking the sun to the entire moon regardless of its rotation. These big freezes would not be conducive to habitability so it is unlikely these moons capable of supporting Earthlike biospheres would ever experience that, which would mean to give a moon planet-like cycles an orbital inclination such that it is never in the shadow of its primary, which would already have to be very large planets to have moons that size. However, even for a gas giant orbit with 0 eccentricity, the orbits of its moons could greatly vary their distances from the system's sun making a "winter" much worse than axial tilt with respect to its sun would. Unless the moon's orbit around its planet would be inclined such that it is nearly perpendicular to the ecliptic.

Of course these gas giants with habitable moons would most likely have to be in the system's Goldilock zone, so they would be totally unlike our star system. Probably more realistic than habitable gas giant moons would be terrestrial double-planet systems orbiting a star (and one or both of the planets are habitable).

Anyway, sorry Sutehp. I haven't come across anything which defines the length of Jedha's day, the length of NaJedha's year, or their star's name. As opposed to making it up, you could just remove those fields from the form (effectively leaving them blank).
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Sutehp
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PostPosted: Fri Jul 21, 2017 4:17 pm    Post subject: Reply with quote

Good lord, I can't believe I totally forgot about the Goldilocks Zone and how gas giants don't tend to be inside it unless (maybe) they're orbiting a star that's a supergiant or something. Yeah, that changes everything.

I'm sure Lucas never thought of that when he created Vavin and Yavin 4 for ANH or the writers of R1 when they created Jedha. At least they were nice enough to keep the Death Star proportionally small when seen next to Jedha, however. (It's only recently that I noticed how the Death Star's superlaser blast in ANH makes Alderaan look like the size of a small moon roughly the same size as the Death Star, rather than a near-Earth-sized planet with a diameter of 12,500km (Earth's diameter is 12,724km).)

And yeah, Whill, you're right: deleting those stats is always an option, one that I'm going to have to bring to Oliver Queen and co. since we may not have a choice in the matter. It feels like a cheat to have to delete those stats entirely, but I like the option of inserting "Duration unknown" or somesuch for the Length of Day and Length of Year even less. In fact, when Oliver Queen gave me the original draft of Jedha's stats, he had included the headers themselves but left them blank. I inserted "XX" into my draft while I hunted for the answers, but as we now know, there aren't any answers to be found. I guess Disney overlooked such minutiae as this when they were making Rogue One. Not that I blame them; it's hardly a relevant detail towards the overall movie.

Back to the drawing board....
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Whill
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PostPosted: Sat Jul 22, 2017 4:25 am    Post subject: Reply with quote

Sutehp wrote:
I'm sure Lucas never thought of that when he created Vavin and Yavin 4 for ANH or the writers of R1 when they created Jedha.

No, Lucas didn't care about that. His thought process was probably "So some gas giant moons in our solar system are as big as terrestrial planets, so what if they were habitable to humans?..." and just went with it, applying gobs and gobs of handwavium. We're talking about the guy wrote that "binary" was a language of load lifters and moisture vaporators, "human-cyborg relations" is a part of C-3PO's job title, and Han Solo made the Kessel Run in less than 12 "parsecs" just because they sounded sci-fi-ish, not because they made sense. Disney Star Wars is mostly just following suit by applying the established "verisimilitudes" of Star Wars.

Sutehp wrote:
At least they were nice enough to keep the Death Star proportionally small when seen next to Jedha, however. (It's only recently that I noticed how the Death Star's superlaser blast in ANH makes Alderaan look like the size of a small moon roughly the same size as the Death Star, rather than a near-Earth-sized planet with a diameter of 12,500km (Earth's diameter is 12,724km).)

Well the movie doesn't show the Death Star and Alderaan in the same shot. The Death Star fires, and then they cut to the shot showing Alderaan and the blast comes from close to the camera and shoots at Alderaan further back. There's really no frame of reference for how far back Alderaan is from the Death Star. (No beautiful shots like we get with the Death Star over Jedha.) ANH established by dialogue that the Death Star is the size of a small moon.
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