Fringian Variant System Description

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

Description / Specifications[edit]

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[edit]

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 Chart[edit]



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, a vacuum inner world
(III) 0.55 AU to 0.85 AU 0.7 AU Venus, a corrosive atmosphere inferno world (orbiting within Sol's H– orbital position)
(IV) 0.85 AU to 1.3 AU 1.0 AU Terra, a standard atmosphere garden world (orbiting within Sol's habitable zone)
(V) 1.3 AU to 2.2 AU 1.6 AU Mars, a very thin atmosphere hospitable world, (orbiting within Sol's H+ orbital position)
(VI) 2.2 AU to 4.0 AU 2.8 AU. a sparse stony planetoid belt
(VII) 4.0 AU to 7.6 AU. 5.2 AU Jupiter, a large gas giant
(VIII) 7.6 AU to 14.8 AU 10.0 AU Saturn, a ringed large gas giant
(IX) 14.8 AU to 29.2 AU 19.6 AU Uranus, a small gas giant
(X) 29.2 AU to 58.2 AU 38.8 AU Shared Orbit: (X-I) Neptune, a small ice giant, and (X-II) the Kuyper Belt (including Pluto), a sparse icy planetoid 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[edit]

Habitable Zone[edit]

The habitable zone (the H zone) is the orbital position around a 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[edit]

The region within a system located starward of the habitable zone. It is 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. It represents the innner region of the habitable zone and marks the limit of where worlds broadly similar to Terra are likely to occur. It may contain hospitable (though generally marginal) worlds.

Outer System[edit]

The region within a system lying spaceward of the habitable zone. It is 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. It represents the outer fringe of the habitable zone and marks the limit of where worlds broadly similar to Terra are likely to occur. It may contain hospitable (though generally marginal) worlds.

Water Worlds[edit]

Ocean-covered worlds with temperate climates are more likely within the H– position, largely to do with the way that such worlds cycle stellar energy. Ocean-covered worlds occuring within the H and H+ zones are generally far colder than their orbital distance would suggest and often have extensive icecaps.

  • worlds lying in the outer system may have subsurface oceans of water or other fluids, entirely covered with a thick crust of ice but kept liquid by the immense pressure, tidal stresses, geothermal activity, radioactive substances or other processes. Examples of this include Europa and Ganymede, two of the moons of the gas giant Jupiter in the Sol system.

Empty Orbits[edit]

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.

Shared Orbits[edit]

Some systems may have multiple worlds sharing the same near-bodean orbital position. In such cases, an additional orbital position is denoted within the bracketed orbital position, separated by a hyphen. An example of this occurs in the Sol System, with both Neptune and the Kuyper Belt occupying orbital position (X).

  • orbital position (X) is considered to lie between 29.2 AU and 58.2 AU from Sol.
    • (X-I) Neptune, the inner element of the shared orbit, orbits Sol at 30.1 AU
    • (X-II) the Kuyper Belt, the outer element of the shared orbit, lies between 30 and 50 AU from Sol. Pluto, the belt's most well-known component, orbits Sol at a mean distance of 39.5 AU.

History & Background / Dossier[edit]

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.


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

Stellar Effects[edit]

Very Large Stars[edit]

Some stars are large enough to encompass inner orbital positions, rendering those orbital positions unavailable due to them being physically within the star. In such circumstances the orbital position at which the star's corona lies is defined and unavailable orbital positions are noted. The scorched metallic cores of dense worlds, remnants from an earlier stage of the system's evolution, may continue to orbit deep within the hot gaseous body of the star.

Companion Stars[edit]

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

Gas Giants[edit]

Gas Giant worlds most commonly form within the habitable zone and the outer system and are usually found in those regions.

Hot Gas Giants[edit]

Occasionally, celestial mechanics and gravitational forces (most probably due to the interactions of multiple large planetary bodies during the evolution of the system, or perhaps disruption 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 or being slung out of the system, instead settle into a stable orbital position close to the star.

  • 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 (a "cthonian world") within a billion or so years. The former atmosphere may exist as a sleet of ionised gases and more complex compounds, with a relatively high density compared to the normal interstellar medium, being carried back through the system on the stellar wind.
  • During their movement into the inner system, hot close gas giants may have cleared orbital positions of existing planetary bodies. Their gravitational influence may have shattered worlds and created planetoid belts, they may have shed their moons during their transit which in turn may have settled into stable orbits around the star and become independent planets in their own right, or they may have "towed" former outer worlds behind them.

Planetary Climate[edit]

The local climate is given a broad classification based on the mean surface temperature of the world

Climate Chart[edit]

Rating Code Temperature (°C) Water (at 1 bar pressure) Lifeforms
Frigid Fr less than -100°C Crystalline ice Cryomorph.
Very Cold Vc between -100°C and -40°C Frozen Hypercryophile.
Cold Co between -40°C and 0°C Frozen, slush, liquid Cryophile. Lower limit of human habitability.
Temperate Tp between 0°C and 30°C Liquid, vapor Mesophile. Optimum human habitability.
A mean surface temperature of between 0°C and 15°C is a Temperate-Cool world.
A mean surface temperature of between 15°C and 20°C is a Temperate-Prime world.
A mean surface temperature of between 20°C and 30°C is a Temperate-Warm world.
Hot Ho between 30°C and 60°C Warm liquid, vapor Thermophile. Upper limit of human habitability.
Very Hot Vh between 60°C and 100°C Hot liquid, vapor, gaseous. Hyperthermophile
Inferno If more than 100°C Boiling liquid, gaseous. Thermomorph
  • Water will have varying properties (such as its boiling point) on worlds with different atmospheric pressures.

References & Contributors / Sources[edit]

This article was copied or excerpted from the following copyrighted sources and used under license from Far Future Enterprises or by permission of the author.