Astrography

Astrography refers to the mapping of space and the topology of celestial objects that make up the universe. The Great War and the events related to it take place in a specific region referred to as Known Space. This is typically defined as the area which encompasses the Local Sector and the Tomastahl Sector.

While the true location of the Void is a matter of scientific (and theological) contention, it is usually considered to be external to Known Space.

Taxonomy
The universe can be observed as having a hierarchical structure. When regarding a galaxy as the highest level component of assembly, the constituent parts can be categorised in sets:

• Galaxies:

Gravitationally bound systems of stars and interstellar matter such as dust and gas.


 * • Arms:
 * While some galaxies are morphologically irregular, spiral galaxies like the Galaxy can be divided into arms; the structures which extend from the galactic core that are made up of billions of stars.


 * • Sectors:
 * Groups of star clusters. Only two sectors exist in Known Space, the Local Sector and the Tomastahl Sector. The boundaries of sectors are artificially defined because they are contingent on the near-insurmountable barriers which exist in travelling between them, not because of any astronomical distinction. The immense distances between sectors means that traversal between them is limited to the most resource-intensive, largest and most technologically advanced starships and as a result they are largely culturally and ecologically isolated from one another.


 * • Clusters:
 * A cluster is a group of systems. Contemporary space travel technology enables imperial navies to move between and patrol multiple systems and therefore many clusters are officially affiliated with specific races. Other clusters are officially neutral while others are the site of conflicts.
 * For a list of clusters in the Local Sector, see Local Sector Astrography.
 * For a list of clusters in the Tomastahl Sector, see Tomastahl Sector Astrography.


 * • Systems:
 * A system composes of a gravitationally-bound area of space caused by one or more stars and typically also refers to the astronomical bodies in the star or stars’ orbit.


 * • Astronomical Bodies:
 * An astronomical body is any contiguous entity which exists in the orbit of a star. Some astronomical bodies are naturally occurring, such as planets, moons, asteroids and comets. Other astronomical bodies can be defined as artificial, such as satellites and derelicts.

The Galaxy
One of tens of millions of galaxies, the Galaxy is a barred-spiral galaxy with a visible diameter of approximately 176,000 lightyears. It contains hundreds of billions of stars and countless planets arranged into spiral-shaped concentrations known as ‘arms’. At the centre of the Galaxy lies the galactic core, a supermassive black hole around which the rest of the galaxy orbits.

Conventionally, the name ‘the Galaxy’ is capitalised to indicate it is a proper noun and refers to this one in particular.

Local Arm
The Local Arm is the spiral arm of the Galaxy which contains the Local Sector and the Tomastahl Sector. The arm is 3,500 light-years wide and approximately 10,000 light-years long. Known Space encompasses only a fraction of the Local Arm with the territories outside the two sectors being largely inaccessible and unexplored by the denizens of Known Space. Travel outside of the Local Arm has not been developed by any race, leaving the rest of the Galaxy shrouded in mystery. What life exists beyond Known Space is indeterminable with the limitations of technology.

Local Sector
A sector in the Local Arm which is native to most of the races involved in the Great War.

See: Local Sector.

Tomastahl Sector
The nearest neighbouring sector to the Local Sector, into which the Great War has expanded.

See: Tomastahl Sector.