The Perseus-Orion Gap

About fifteen hundred light years rimwards of Sol is the gap between the Orion–Cygnus Arm (in which Sol is located) and the larger Persus Arm. Whilst not entirely devoid of stars and stellar bodies, the density of viable systems drops significantly, with older stars being more prominent, with few planetary bodies or areas of interest to encourage colonisation. The FourDrive is more than capable of traversing this gap, and exploration missions have crossed it on a number of occasions, but the increase in travel time and the lack of 'stop-over' systems to keep journey times to a minimum have meant that it remains a significant safety and psychological barrier to human expansion in that direction, much like the gap between the Orion Arm and the Carina-Sagittarius Arm in the Coreward direction.

Geography

Away from the relatively high stellar density of the galaxies spiral arms, interarm gaps are not entirely empty, but the distance between stars, nebulae and other areas of interest grows substantially. Additionally, the age of the stars in these gaps is greater; far fewer energetic stars with complex planetary systems and opportunities for colonisation and exploitation. Instead the void is filled with old red giants, white dwarves, and neutron stars - interesting from an scientific perspective, but with little going for them in any other area.
A few settlements do exist within this area, typically from cultures seeking extreme isolation from the rest of humanity, but unless they remain quiet, they become attractive annexation targets for both the Federation of Xah and the Northup Alliance. The total number of colonised systems is unknown, but probably fewer than a thousand, and suspected to be in in the low hundreds, with a total population of only a few billion, spread across an area a couple of hundred of lightyears across.

History

The existence of the Gap has been known about since the early days of galactic mapping, when it was was first realised that the Milky Way galaxy was in a barred spiral shape. When exploration vessels first reached it, there was some trepidation about jumping that distance through FourSpace, as the time taken for the calculations would be substantial. Longer jumps had been done in the past, but they were risky, and the time taken for a FourDrive jump increases exponentially above 1000 light years; a 1000 light year jump should take only a few hours, assuming the topology in Fourspace is favourable, whereas a jump of 2000 light years takes at least nine days. The more time spent in Fourspace increases the dangers of being lost, so most ship captains prefer a series of smaller jumps, despite the increase in energy costs.
The first transit of the Gap is not recorded, and probably occured at some point in the Great Expansion with the records lost since then. These days, only a dozen attempts are made each year, almost all of them scientific surveys, with the occasional brave souls seeking a new home in the blackness of deep space.

Milky Way Arms

The Gap is between the Perseus arm and the Orion-Cygnus Spur, rimward of Sol

Alternative Name(s)

The Gap, The Rimward Void

Type

Expanse

Included Locations

• Ghosmer