Mapping political boundaries in the Milky Way galaxy

Question

Background

The Salutary Suzerain Eashmeelthfluischaotchaulpcreurmmoelshchurbshrulth (we call him The Great Eel, now kneel!) has declared that in His Greatest Beneficence, He shall divide the Galaxy such that His vassal protectorates shall be blessed with the feeling of independence. Declaring that His Sanctitude shall last no less than one million years, His Eternal Asphyxiation¹ commands a map of the Milky Way galaxy that shall define and denote said boundaries for the necessary period of time.

Question

How can I define a map of the Milky Way galaxy that divides it roughly into thirds using the center of the galaxy as the primary reference point like a pie chart such that as the galaxy and surrounding universe chug along for one million years the map continues to be relevant?

Conditions

1. If it simplifies things, deal with the map in two physical dimensions. Assume that extrapolating the answer into the third physical dimension won't be beyond the abilities of The Great Eel's astromancers.

2. Everything's in motion and so a trivial answer would be to ditch the pie chart and use concentric rings, each ring having roughly the same number of stars (or, if one happens to know them, habitable planets). But trivial is boring and royalty isn't necessarily known for being the brightest bulbs in the room (don't let that get back to the Eel's ears!). So, knowing that stars close to the center generally orbit the center very quickly and those at the rim tend to orbit very slowly... The Great Eel nonetheless wishes a meaningful Triadic Cartograph.

3. Just to make things interesting, The Great Eel insists that His planet never falls into the domain of one of his vavasours. So the goal is to figure something out that keeps all the stars that initially exist in a simple three-piece pie chart of the galaxy (looking down from the "top," whatever that really means) in a contiguous grouping one million years later.

4. Planets too near Sagittarius A (the Milky Way's central black hole) experience a host of problems that make both this calculation and their utilization difficult if not impossible. I'm happy to exclude everything within 10 light years of the center. (Although another question might ask, just how close to the center of the galaxy can one get for (a) habitability and (b) mining purposes before it's no longer useful to do so?)

Final note

It is my assumption that all "star maps" defining political boundaries in any galaxy will suffer dissolution over time. Even declaring a star system "mine" will be a difficult claim to protect depending on the galactic orbit of that star compared to all the other stars that are "mine." Said another way, it may not be possible to declare a contiguous galactic empire over long periods of time in any ways other than concentric rings or as a single galaxy-wide empire. This question is testing that theory. Therefore, so long as the answer is documented or justified (hence the hard-science tag), "it can't be done" is a justifiable answer.

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_{¹ As in "his glory shall leave you breathless" vs "he who shall take your breath away," although depending on the circumstance there may not be much of a difference.}

Answer 1

This is impossible, if I've understood your conditions correctly.

There are several reasons for this:

1. Stars move as they orbit the Galaxy's center of mass. You're already aware of this, as you (correctly) note that using a static pie chart will result in stars drifting into different sectors over time.
2. Stars in different orbits move with different angular velocities. This means you can't even have a pie chart that rotates along with the Galaxy. Stars nearer the Galactic core will, over time, get ahead of their sector; whereas stars closer to the rim of the Galaxy will lag behind.
3. Not all stars orbit the Galactic core in the same direction. Some go backward. Others have inclined orbits that don't keep them within the Galactic plane.
4. Stars' orbits are not circular. This means even your "concentric rings" idea won't work, as stars near the boundaries between the rings will drift in and out as they orbit. (Most stars' orbits are roughly elliptical, but they're not Keplerian orbits with one focus at the Galactic core- rather, the Galactic core is at the center of the ellipse, and the stars move in and out two times each orbit. This happens because, unlike with planets orbiting a star, the Galaxy's mass is not all concentrated in its core. The Galaxy's mass is distributed much more evenly across its volume.)

You could define your map's boundaries to move along with the average bulk motion of the stars near the boundary, which would result in the boundaries twisting around the Galactic core over time. But this would not be able to account for individual stars with slightly different velocities than their neighbors (which could cause them to drift over the boundaries over time), and wouldn't work for stars on heavily inclined or retrograde orbits at all.

Probably the best you're going to get is for The Great Eel to issue a decree that goes something like this:

"All stars that are within this geometrical volume of the Galaxy as of the time this broadcast reaches them shall for the next million Earth-years be considered under the jurisdiction of District A, no matter where their orbits within the Galaxy take them. Likewise for the stars that this broadcast finds in this other geometrical region and District B, and for this third geometrical region and District C."

The "as of the time this broadcast reaches them" bit is important, especially if you don't have FTL communication. Otherwise it could be hard to tell exactly which region some outlying stars were in at the time His Eternal Asphyxiation made the decree.

I expect your citizens would eventually create a database listing every star in the Galaxy along with exactly which district has jurisdiction over it. This would be the only way to keep track of who owns which stars in the long term. This would also allow stars to swap to other districts if doing so is politically convenient, e.g. if a star happened to diffuse into an area surrounded by stars from a different district.

There would also need to be laws concerning what district can claim a newly-born star, since stars are being born all the time. But there are many different ways that could be handled.

• Galaxy rotation curve on WP.

• Galactic year on WP, with a spectacular animation of the evolution of the positions of a numerous bunch of stars during the last 225 million years, which is what it took the Sun to make one round trip around the galaxy center.

Answer 2

Two halves and a central zone!

His Holiness' planet forms an axis with the black hole, and it shall separate the galaxy into a left and a right halve. Anything closer to the black hole than a certain distance shall be known as the first state, anything ouside of it and left of the holy planet shall be the second, and anything outside of it and right shall be the third state. Since the line between the second and third state shifts with His Holiness' planet, some planets might shift ownership over a million years, but not too many, as the most difficult mappting problem was solved by putting the first state inside a specified radius of the black hole.

By defining only a distance to the black hole and a single axis, which can be observed and tracked somewhat easily, the shifting of worlds to other sectors over time can be not just tracked, but pre-calculated, and the different states can negotiate for a peaceful transition of any system that moves too fast or too slow and falls into a different region over time

Answer 3

Corridor Worlds

At the start, the galaxy is divided into three slices. But the slices have some holes in them, which are not controlled by anyone but the Great Eel. These holes are the Corridor Worlds.

Let's say we have three rulers and the Great Eel. Baron Greedyface, Duchess Poorhater and King Bigbully.

After some years, Greedyface sees that part of his domain is about to be cut off and surrounded due to orbiting stars. However, at this moment the Great Eel's superior intelligence and infallible plan make themselves known.

The Corridor Worlds align, and so too do the timings of their leases which say that after this amount of time they should fall into the hands of Greedyface. Now, there is a corridor of territory connecting Greedyface's domain together. This is the basis of Corridor Worlds.

As time goes on, more Corridor Worlds "activate" and end up creating a sort of tangle, with big blobs connected by thin lines. But they are connected. Anyone who wishes to pass through an inactive Corridor World shall be denied passage by order of the Great Eel, so that they are basically dead space until activation.

Crossroads Systems

After a while, Poorhater's domain looks like a starfish, with many branches and long lines of other people's territory sticking in. To move from one tip of a branch to another, you must either

a) pass through enemy space

b) go all the way down the arm to the center and up again

However, the all-knowing Great Eel, O hear His name and bow, has devised a clever solution. Here is where Crossroads Systems come in handy. These are star systems with multiple Corridor Worlds that will be handed to different rulers, allowing them to both pass through. Now you can just go directly from tip to tip and only use friendly spaceports.

Carrot Ports

Say Bigbully now wants to rebel and take over the empire. Luckily, the Great Eel in his infinite genius has foreseen this threat and prepared a clever defense. In the event that a vassal rebels, spaceports are promised to whoever defeats the rebellion.

This means that no one wants to rebel, but if it does happen they will be fine and will not lead to a massive power vacuum. It is just that their enemy will be in a good strategic position. This idea applies to certain worlds that are not given by default to anyone but hold strategic importance.

It also works for other things like when the Great Eel needs to raise funds, he can simply rent out one of these strategic ports for a set period, maintaning military control and only allowing whichever vassal paid him to pass through. The ports are like a carrot to control his vassals.

Conclusion

I will leave the placement and timings of these special worlds up to the Great Eel's astromancers. All hail the Great Eel, Master of Void and Star, Bearer of Omniscience, Divinely Mandated, O hear His name and bow.