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A look at how things are named and numbered in the universe.

See also the Planetary Classification List.

The Galaxy

The four directions in the galaxy are Coreward, Rimward, Spinward and Trailing.

Coreward is towards the core of the galaxy, and is generally 'up' on galactic map.

Rimward is towards the rim of the galaxy, and is generally 'down' on galactic maps.

Spinward is in the direction of galactic spin, and is generally to the 'left' on galactic maps.

Trailing is opposite the direction of galactic spin, and is generally to the 'right' on galactic maps.


Each Sector may have its own local name, and the method used to select a name is undefined. The local name may be Foo Rift or Spinward Cluster. There is no methodology to how such names are defined.

However, each sector has two official designations - one being its coordinate, and the other being a default name based on its position in the galaxy.

One sector is defined as 'Sector 1', and always has coordinates 0,0.


Each sector has an X and Y coordinate. Positive Y is in the direction of Rimward, i.e. down on galactic maps. The higher the Y coordinate, the further from galactic centre the sector is. Conversely, negative Y is in the direction of the galactic core, so is up on maps.

Positive X is Trailing (to the right), and negative X is Spinward (to the left) on maps.


The 0,0 sector is named 'Sector 1'. All other sectors also have a number, and this is counted by spiralling out away from 'Sector 1', going to (0,-1) 'Sector 2', then (1,1) for 'Sector 3' and so on. The diagram below shows the starting pattern.

25 10 11 12 13
24 9 2 3 14
23 8 1 4 15
22 7 6 5 16
21 20 19 18 17

Sectors further away from the Core will have higher numbers.


Stars are named for the system they are in. If there is a single star in the system, then it is simply “Name”. If there are multiple stars, then each star is given a suffix in order of mass based on Greek letters.

The most massive star is “Name Alpha”, the second star “Name Beta”, the third “Name Gamma” etc.


Planets are named for the system they are in, with a Roman numeral suffix in order of distance from their star. e.g.:

  • Name I
  • Name II
  • Name Alpha III

In the third example above, the planet is the 3rd planet from the first star in a multi-star system.


Moons are named after the planet, with a lower case letter suffix starting at 'a' and in order of distance from the planet. So Earth's Moon is Sol III/a.


Rings encircle a planet. They use an arabic numeral prefixed with 'r'. So Sol V/r1 would be the first ring of Jupiter.


Belts are a special case, and use their own counting scheme. A belt is named with a capital letter starting with A, and counting upwards.

Significant objects (normally asteroids) within a belt may be given their own designation. They are counted from innermost to outermost, using lower case Roman Numerals after a slash. e.g. A/i, A/ii, A/iii for three objects within Belt A.

Internally, these are treated as moons, though the term 'planetoid' is normally used.

nomenclature.txt · Last modified: 2018/10/23 19:04 by sam