Planetary Profile: Duskara

Host Star

• Name: HD Xanthea (colloquial: “The Lion”)
• Spectral Type: M0–M1 main-sequence star (a red dwarf at the warm end of its class)
• Mass: ~0.55 Solar masses
• Luminosity: ~0.05–0.06 Solar luminosities
• Estimated Age: ~4–5 billion years
• Activity: Quiet for a red dwarf, but still prone to flares that feed Duskara's auroras and disrupt communications
• Habitable Zone: Close-in orbits, where planets are tidally locked

Orbital & Planetary Characteristics

• Planet Name: Duskara
• Orbital Distance: ~0.17 AU from HD Xanthea (varies slightly with eccentricity)
• Orbital Period: ~34.7 Earth days, one Cycle (synchronous rotation leads to tidal locking)
• Stellar Flux: Roughly twice what Earth receives from the Sun
• Rotation: Tidally locked (one hemisphere faces the star constantly)
• Axial Tilt: Minimal (≤ 1°), little to no seasonal variation

Physical Properties

• Diameter: ~1.00–1.05 × Earth’s diameter
• Mass: ~1.00–1.10 × Earth’s mass
• Surface Gravity: ~0.95–1.05 g (near Earth-normal)
• Escape Velocity: Similar to Earth’s (slightly higher or lower depending on precise mass/radius)

Day–Night Temperature Extremes

• Day Side:
  • Surface Temperatures: ~80–150°C, hottest around the substellar point
  • Intense stellar flux, extreme UV and particle radiation
  • Frequent dust storms in transition zone
  • Minimal or no standing water at the surface
• Night Side:
  • Surface Temperatures: ~−60 to −100°C, coldest around the antistellar point
  • Permanently dark or in deep twilight from scattered auroras
  • Glacial ice sheets, occasional geothermal vents or volcanic hotspots
  • Some pockets of life in subterranean areas warmed by geothermal heat

Twilight Belt

• Width: ~200–300 km band encircling the planet (about 40,000 km long)
• Settled Arc: About 6,000 km of the belt (Daŋa-Hai, the Living Edge), where night-side glaciers supply water; the remainder is unsettled
• Temperature Range: Generally −5°C to +40°C, depending on proximity to day or night side
• Atmospheric Dynamics:
  • Strong, persistent winds due to stark temperature gradient
  • Frequent superstorms where hot and cold air masses meet
• Habitable Zone: Nearly all surface settlements and farmland lie here; major cities form linear chains along temperate corridors

Atmosphere

• Composition (approx.):
  • ~76–78% Nitrogen (N₂)
  • ~20–22% Oxygen (O₂)
  • ~1–3% Argon / other inert gases
  • Trace amounts of CO₂, H₂O vapor, and exotic molecules
• Surface Pressure: ~0.9–1.1 bar (near sea-level Earth equivalent)
• Radiation & Weather:
  • Enhanced stellar radiation on the day side; partial protection via thick atmosphere
  • Robust wind circulation redistributing heat and moisture from day to twilight regions

Water & Geological Features

• Primary Water Reservoirs:
  • Subterranean aquifers, glacial deposits on the night side
  • Collection of atmospheric moisture in twilight and day-night transition storms
• Surface Water:
  • Rivers that run dayward across the belt and end in the salt flats of the Dayward Edge, and the freshwater Bahari in the rift of the heartland
  • Fed by glacier melt, storm runoff and geothermal springs; the flow rises and falls with glacier surges and storm phases
• Geology:
  • Tectonically active regions produce geothermal vents, crucial for night-side warmth
  • Abundant mineral deposits in dayward highlands, mined by robotic systems; the ores are plentiful, but only robots reach them, and the capacity to refine and work them is small

Why the Twilight Belt Is Habitable

• A dry world: Duskara has no oceans. With little water vapor in the air, the greenhouse effect stays weak, and the planet avoids the runaway heating that would sterilize a wetter world at this distance from its star.
• Water locked in the night: Nearly all of Duskara's water sits frozen on the night side, which is cold enough to hold it but not to freeze the air. Glaciers creep toward the Nightward Edge and melt there, feeding the rivers, aquifers, and storms of the belt. They reach the belt only along one arc of the ring, which is why the settled world is an arc and not a ring, and why night-side ice matters so much.
• Water passes through: The Living Edge has rivers and a lake, but little water that stays. The ground falls from the ice to the day side, so every river runs dayward and ends in the salt flats. The warm, dry wind takes water from every open surface, most of all in the dayward half of the belt. The melt comes in pulses with glacier surges and storm phases, and a full river can be low two Cycles later. Raw melt water carries dissolved carbon dioxide, rock flour and minerals, and it must be treated before people drink it. Water is least scarce in the Ice Land, where the glacier tongues are longest, and most scarce in the Dry Land, where no river runs. Water on Duskara is not rare; it is brief. A settlement catches it, uses it, cleans it and gives it back. This is what Duskarans mean when they call water scarce.
• Wind as heat engine: The thick atmosphere carries day-side heat across the terminator and returns cold air beneath it. This is why neither side reaches the extremes of bare rock: without air the point under the star would pass 150°C, and the night side would fall far below −100°C. The eternal wind and the storm walls are the visible face of that circulation, and they keep the belt between −5°C and +40°C.
• Magnetic shelter: A strong planetary magnetic field turns aside most of the star's flare radiation. What gets through lights the auroras.

Ecology & Life

• Native Flora & Fauna:
  • Adapted to low light, high winds, or subterranean niches
  • Some species show bioluminescence or specialized thermal regulation
  • Deep-cave ecosystems rely heavily on geothermal/chemosynthetic processes
• Human Settlements:
  • Concentrated in twilight belt, forming linear “wind-hardened” cities
  • Cave-dwelling communities near geothermal vents on night side
  • Careful agriculture (vertical farming, hydroponics) in stable twilight microclimates

Key World Constraints

• Tidal Locking → Eternal day side and perpetual night side
• Severe Wind Patterns → Massive storms at the day-night interface
• Water as a Flow → Much passes through, little stays; catching, cleaning and sharing water is the core work of every settlement
• Rich in Energy, Poor in Matter → Wind and geothermal power are plentiful; metal, parts and the capacity to make them are not
• The Awakening → Psychic gifts of unknown origin shape work, law and faith
• Geothermal Relief → Vital for warming settlements in night-side caverns