A Canonical Size for the Star Wars Galaxy?

[Moff Tarquin]

While I was getting my copy of TFA:ICS, I found something interesting in the TFA Visual Dictionary: a map of the Star Wars galaxy. Since these materials are Disney-canonical, this might allow us to calculate the size of the Star Wars galaxy.

This map is the same as the one in the book:



Tatooine and Geonosis - which are less than a parsec away from one another - are clearly labeled on the map. Find the distance between them, find the size of the Galaxy Far Far Away.

Just by dumping it into Microsoft Paint, the center of Geonosis looks to be at (577,771), and the center of Tatooine looks to be at (580,765). According to the Pythagorean theorem, that means that they are some 6.7 pixels apart. The galaxy in its entirety looks to be about 850-860 pixels wide. Which, at 6.7 pixels to the parsec, is between 126 and 129 parsecs - or between 411 and 421 light years.

Seems a little small for a spiral galaxy to me, but it looks like it's canon now.

[Mike DiCenso]

I'm not sure if there is enough separation between Geonosis and Tatooine to determine such a thing seeing how much their respective stars overlap each other. Also interesting is that Bespin and Hoth appear to be in the same star system now, or at least the two systems are close enough to look like they are the same, which neatly solves that old dilemma.
-Mike

[Moff Tarquin]

I really wish they showed where Alderaan used to be. It'd be nice to know.

[359]

It is also a shame they do not list Toydaria and Ryloth, as that could also be used to get a general estimate on the galaxy's scale using TCW: "Supply Lines."

Then again, Endor and Sullust are described as being "hundreds of light-years" apart in the novelization for Return of the Jedi. But that would put the galaxy at ≈4,000 ly in diameter using 1000 ly for the trip. If we push the use of "hundreds" out to something like 'fifteen-hundred' light years approaching a limit of 2,000 ly, which is reasonable verbal usage of the words, we get a galaxy that is ≈8,000 ly in diameter. However, from TCW: "Supply Lines" we get that the galaxy can not reasonably be that small in order to fit with that episode as seen here.

So we can say with certainty that the galaxy is not large, and is of small and modest size, but we can not pinpoint exactly how large it is. I would guess it would be in the 20,000 ly - 30,000 ly range.

[Mike DiCenso]

Can we even assume they would be traveling in a straight line in "Supply Lines"? After all, a GFFA of 8,000 ly would have a circumference of around 25,132 ly, so making a 6,000 ly run in such a galaxy isn't too far fetched.
-Mike

[359]

I think we can assume close enough to straight lines, much like our modern highway network. Especially since they were discussing the relative range of one location to another. It would make no sense to go all the way around the galaxy to get somewhere.

And it's not just that the run is that long, that's the shortest it could possibly be. The planet Toydaria is 2,000 parsecs closer to Ryloth than the nearest fleet. That means the distance to the nearest fleet is greater than 2,000 parsecs. So since Ryloth is in the outer rim it would make sense that the nearest Republic fleet be more in the direction of the core because that is where the Republic is based, presumably with the fleet needing to hold its position for some reason or another. From this we can determine that the radius of the galaxy must be significantly greater than 6,000 ly. At its smallest, there must exist a point on on the outer rim that is 6,000 ly further out than the edge of the inner rim.

[Moff Tarquin]

Modest doesn't necessarily mean "small." It just means "not particularly large."


As a point of fact, spiral galaxies range from 1e9 solar masses to 1e12 solar masses, with typical ones being 1e11 solar masses. Dimensions range from a diameter of 5 kiloparsecs to a diameter of 100 kiloparsecs.

With a bit of analysis, we can get a regression going.

5 kpc, 1e9 solar masses

100 kpc, 1e12 solar masses.

Take the logs of everything:

log(5), 9

2, 12

The slope of this line is: 3/(2 - log(5))

if y = log(galaxy mass in solar masses), and x = log(galaxy diameter in kiloparsecs),

y = (3/(2 - log(5)))x + b

Plug numbers in and solve for b:

12 = (3/(2 - log(5)))(2) + b
12 = (6/(2 - log(5))) + b
b = 12 - (6/(2 - log(5)))

So:

y = (3/(2 - log(5)))x + 12 - (6/(2 - log(5)))

When y = 11, x = 1.566323.

10^1.566323 = 36.8403 kiloparsecs.

So really, all we can say about the Star Wars galaxy is that it's 37 kiloparsecs or less in diameter. That's almost exactly 120,000 light years. 120,000 light years is an average sized galaxy. Whether "modest" is consistent with "average" in context is debatable, but "modest" certainly doesn't mean "particularly small."

If I had to guess, I'd say that the Star Wars galaxy is "below average," but that's more than consistent with a diameter of, say, 22 kiloparsecs, or 73,000 light years.

At any rate, trying to compress the Star Wars galaxy beyond 16,000 light years without canon evidence is completely unjustified. If we can't get a size from the Disney-canon map, we really have no reason to think that the Galaxy Far Far Away is any different in size from our own.

[359]

Indeed modest does not necessitate that the galaxy be small, it is the relative distance and positions of Sullust and Endor that does, which is a canon example. However on the other hand we have another canon example that requires it to be substantially larger with the relative positions of Toydaria, Ryloth, and the Republic. Thus a middle ground between average and tiny at around 30,000 ly.

[Mike DiCenso]

I think we can assume close enough to straight lines, much like our modern highway network. Especially since they were discussing the relative range of one location to another. It would make no sense to go all the way around the galaxy to get somewhere.

And it's not just that the run is that long, that's the shortest it could possibly be. The planet Toydaria is 2,000 parsecs closer to Ryloth than the nearest fleet. That means the distance to the nearest fleet is greater than 2,000 parsecs. So since Ryloth is in the outer rim it would make sense that the nearest Republic fleet be more in the direction of the core because that is where the Republic is based, presumably with the fleet needing to hold its position for some reason or another. From this we can determine that the radius of the galaxy must be significantly greater than 6,000 ly. At its smallest, there must exist a point on on the outer rim that is 6,000 ly further out than the edge of the inner rim.

Depends all on where you're navigation to and from, now doesn't it? Right now, can think of just several, if the route has to take Western Reaches to the Expansion Region first, then high tail it coreward. And in all of this, isn't it interesting that we see so many habitable worlds so deep inside the galactic core? Conversely, we can have a route from the Outer Rim, across the Core and to the other side of the galaxy (near Dantooine) that would make the whole thing no more than 25 k lys. We just don't have enough information.

SPOILERS!
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Anyone seen any good screencaps yet of the Skywalker Map seen at the end TFA that BB-88 and R2-D2 put together? That's probably flat out one of the best galaxy maps seen to date, especially if it has some recognizable landmarks that'll show up in close up examination. Would be interesting to compare it to the Visual Dictionary map as well.
-MIke

[359]

Depends all on where you're navigation to and from, now doesn't it? Right now, can think of just several, if the route has to take Western Reaches to the Expansion Region first, then high tail it coreward. And in all of this, isn't it interesting that we see so many habitable worlds so deep inside the galactic core? Conversely, we can have a route from the Outer Rim, across the Core and to the other side of the galaxy (near Dantooine) that would make the whole thing no more than 25 k lys. We just don't have enough information.

Indeed we do not have enough information to be exact, but we do have enough to create a reasonable minimum. We know that Toydaria is closer than the nearest republic fleet. We also know that the Republic dominates the inner rim and that Ryloth is in the outer rim. Presumably there exists a republic fleet within the inner rim, in fact there should be a great many. and there should be some outside it as well. But anyway, let's say that's the closest fleet, unlikely but provides a lower limit on the galactic size, then there exists a point within the outer rim that is 6,000 ly radially distant from the edge of the inner rim. So given the comparison of the major axis of the outer rim to the minor axis of the inner rim that should yield a galaxy with a radius of absolute minimum 7,000 ly.

Yes, hyperspace does not travel in exactly straight routes, but we have yet to see any that take "the scenic route" as it were. In fact we have seen several paths that zig-zag a bit, but are going within 10° of the overall direction. Additionally this forces that the Republic not have a fleet in effectively a whole 1/3 of the galaxy. A third that, no doubt, contains Republic worlds as Ryloth itself is a Republic world. Furthermore, it being a Republic world would suggest that it is not on the very outer reaches of the galaxy as was calculated above, since clearly Kamino is considered to be even more distant at "beyond the outer rim" yet still within the galaxy. And evenfurthermore (yes I know that's not a word) 6,000 ly is the minimum distance the fleet is to Ryloth because it assumes Ryloth and Toydaria are adjacent or near adjacent systems. Otherwise the distance would be some sum of 6,000 ly + sin(angle offset of Toydaria) * (distance to Toydaria). Hence my guess at a 30 kly diameter galaxy as a compromise between this clearly far larger size and the too small size calculated by Sullust –> Endor.

[Mike DiCenso]

Well, the two systems can't necessarily adjacent to one another, just that one is 2,000 parsecs closer than the nearest fleet. As far as zig-zagging goes, we have seen in "Shadow of Malevolence", the Malevolance had to actually go 15 parsecs out of her way to go around the Kaliida Nebula to get to the Republic's Kaliida Shoals Medical Center to attack and destroy it. So direct routes straight to a destination are not always guaranteed. But I find it curious that Toydaria is not listed on this map. It would really help pin a lot down, if it was.
-Mike

[359]

They can be adjacent, it's just highly unlikely. Because all we know is that the distance is 2,000 parsecs less than it is to the fleet. So if the systems were separated by say 10 parsecs then the fleet would be 2,010 parsecs away given Toydaria is 2,000 parsecs closer at 10 parsecs. More reasonably, since we are talking about fuel limitations, it should be quite some distance away to make that a reasonable need for a stop, making the total distance to the fleet 2,000 + d parsecs; where d is the distance between the two systems.

Indeed the Malevolence did need to circumvent a nebula, but that is hardly the same thing as taking a trip around a nebula. And as I said, it's not going to double the path length, or anything near that.

[Praeothmin]

The "modest-sized" discussion?
Again?

While "modest" does not mean "small", it cannot be big either, and 120 kly across is a friggin big spiral galaxy...
I agree with 359, 20 kly to 30 kly seems to fit most numbers given in scripts, movies/series and books...

[Mr. Oragahn]

Tatooine and Geonosis - which are less than a parsec away from one another - are clearly labeled on the map. Find the distance between them, find the size of the Galaxy Far Far Away.

Just by dumping it into Microsoft Paint, the center of Geonosis looks to be at (577,771), and the center of Tatooine looks to be at (580,765). According to the Pythagorean theorem, that means that they are some 6.7 pixels apart. The galaxy in its entirety looks to be about 850-860 pixels wide. Which, at 6.7 pixels to the parsec, is between 126 and 129 parsecs - or between 411 and 421 light years.

Seems a little small for a spiral galaxy to me, but it looks like it's canon now.

I don't think it's to be taken too literally. It's a general representation of things. Two stars nearly overlaping means they're very close to each other, but not from the same system.
Tatooine has two suns but they're not represented on this map either.

[Mr. Oragahn]

I'm not sure if there is enough separation between Geonosis and Tatooine to determine such a thing seeing how much their respective stars overlap each other. Also interesting is that Bespin and Hoth appear to be in the same star system now, or at least the two systems are close enough to look like they are the same, which neatly solves that old dilemma.
-Mike

Bespin belonged to the Anoat system.
If on the map, two systems located less than one parsec from each other get shown as two separate compounds, then clearly both Hoth (which was mentioned as its own system iirc) and Anoat must be even closer. Both Hoth and Bespin's respective luminosities indicated that they were not far from their respective stars (we see Bespin's as the Millennium Falcon approaches the Cloud City). Those two systems must be locked in some odd pattern. Very close to each other, either both orbiting around a barycenter or perhaps one orbiting the other.
This reminds me of the strange arrangement of planet distribution for the reimagined Battlestar Galactica and its Twelve Colonies star systems: they were distinctive systems but somewhat very close to each other.

It may be a satisfactory solution to that old problem of transit duration. There won't be any mention of auxiliary hyperdrive anymore; all the distance was crossed by the MF at sublight speed, which would still require a lot of time but give enough to Luke for his training to look more believable than the equivalent of some Jedi speed dating.