Fringian Variant System Description

The Fringian Variant System Description is a means of describing a star system.

Introduction

Fringian Variant System Descriptions are described using a layout and structure pioneered by the University of Tal Varisa and accepted as a standard across the Distant Fringe region.

Stars

Stars are named and described. Their characteristics are measured using Sol, Terra's primary star, as the mean.

Secondary stars and brown dwarfs are generally noted as Subsystems, depending on their orbital position. Each has its orbital and physical characteristics defined, and details of any stellar system that it retains are provided.

Orbital Positions

Worlds orbiting stars within the Distant Fringe region broadly fall within orbital positions predicted by the Titius–Bode law, and are usually referred to as having near-Bodean orbits. Distances are measured in Astronomical Units (AU): one AU is equivalent to the distance between Terra and Sol, or 149.6 million km.

Orbital positions are denoted by a bracketed roman numberal. Each orbital position defines a set distance from the star (a span) measured in AU, as defined on the table below:

Orbital Position	Span	Mean Distance	Sol System Equivalent
(I)	0.01 AU to 0.3 AU	0.2 AU	Empty Orbit
(II)	0.3 AU to 0.55 AU	0.4 AU	Mercury
(III)	0.55 AU to 0.85 AU	0.7 AU	Venus (orbiting within Sol's H– orbital position)
(IV)	0.85 AU to 1.3 AU	1.0 AU	Terra (orbiting within Sol's habitable zone)
(V)	1.3 AU to 2.2 AU	1.6 AU	Mars (orbiting within Sol's H+ orbital position)
(VI)	2.2 AU to 4.0 AU	2.8 AU.	Planetoid belt
(VII)	4.0 AU to 7.6 AU.	5.2 AU	Jupiter
(VIII)	7.6 AU to 14.8 AU	10.0 AU	Saturn
(IX)	14.8 AU to 29.2 AU	19.6 AU	Uranus
(X)	29.2 AU to 58.2 AU	38.8 AU	Neptune, Kuyper Belt
(XI)	58.2 AU to 116 AU	77.6 AU
(XII)	116 AU to 231 AU	154 AU
(XIII)	231 AU to 460 AU	308 AU
(XIV)	460 AU to 920 AU	615 AU
(XV)	920 AU to 1850 AU	1230 AU
(XVI)	1850 AU to 3700 AU	2460 AU
(XVII)	3700 AU to 7400 AU	4915 AU	Sol's Oort Cloud
(XVIII)	7400 AU to 15000 AU	9850 AU	Outer edge of Sol's Oort Cloud

Orbital Zones

Habitable Zone

The habitable zone of a system is the orbital position around the star where the energy from that star falling on a hypothetical Terra-like world would produce moderate temperatures and allow liquid water to exist. These conditions are the most likely to allow life, both native or introduced, to survive without artificial assistance. Smaller, less energetic stars may not have a habitable zone. Not all worlds that orbit within a habitable zone are habitable, or even hospitable.

Inner System

The region within a system located starward of the habitable zone, and generally too hot to allow liquid water, breathable atmospheres or advanced forms of life. Smaller, less energetic stars may not have an inner system.

• The orbital position directly starward of the habitable zone is defined as the H– zone and may contain hospitable (though generally marginal) worlds. Temperate ocean-covered worlds are also more likely within the H– position, largely to do with the way that such worlds cycle stellar energy.

Outer System

The region within a system lying spaceward of the habitable zone, and generally too cold to allow liquid water, breathable atmospheres or advanced forms of life. Local conditions and circumstances may dramatically affect this, however. The mechanics of star system formation mean that gas giants are more likely to occur within the outer system. Smaller, less energetic stars may only have an outer system.

• The orbital position directly spaceward of the habitable zone is defined as the H+ zone and may contain hospitable (though generally marginal) worlds.

Empty Orbits

Some systems may not have worlds filling every available near-bodean orbital position. In such cases, these are defined as empty orbits and are noted as such. An example of this occurs in the Sol system, with orbital position (I) (lying 0.2 AU from the star, inside of Mercury's orbit) being defined as empty.

Stellar Effects

Large Stars

Some stars are large enough to encompass inner orbital positions, rendering those orbital positions unavailable. In such circumstances the orbital position within which the star's corona lies is noted.

Companion Stars

The presence of one or more companion stars orbiting the primary may render certain orbital positions available. This is noted in the system description.

Gas Giants

Gas giant worlds most commonly form within the habitable zone and the outer system and are most commonly found in those regions. Occasionally, celestial mechanics and gravitational forces (perhaps generated by the passing of a wandering star) may cause gas giant worlds to migrate inward through the star system. Some, rather than burning up in the star's photosphere, instead settle into a stable orbital position close to the star, typically within 0.3 AU (orbital position (I), 45 million km).

• Hot close gas giants are relatively young in terms of stellar evolution. The energy streaming off of the star gradually strips away their atmospheres, typically reducing them to a dense near-vacuum core remnant within a billion years.
• Inner gas giants may have cleared planetary orbits of existing planetary bodies, their gravitational influence may have shattered worlds and created planetoid belts, or they may have shed their moons during their transit, which in turn may have settled into stable orbits around the star and become worlds in their own right.

Notes

This system of describing star systems, while broadly used within the Distant Fringe, is not utilised elsewhere.

References & Contributors / Sources

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This list of sources was used by the Traveller Wiki Editorial Team and individual contributors to compose this article. Copyrighted material is used under license from Far Future Enterprises or by permission of the author. The page history lists all of the contributions.

• Author & Contributor: Lord (Marquis) and Master Scout Emeritus Adie Alegoric Stewart of the IISS
• Author & Contributor: Lord (Marquis) and Master of Sophontology Maksim-Smelchak of the Ministry of Science