settled-reach/wiki/star-systems/GJ-107A/index.md

Tình Yên

GJ 107A | F-type | east_reach

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System Profile

Star	F7V · 36.3 ly
Bodies	0 habitable · 2 inhabited
Gates	1 aperture · dead_end
Settlement	wave_3
Industries	fusion_fuel, metallic_ore, lattice_grade_material, hospitality, financial_services, legal_services
Exports	lattice_grade_material, financial_services
Imports	processed_food, electronics, consumer_goods, medical_goods, refined_metals, heavy_equipment
Population	—

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Tình Yên means "peaceful," and the name is slightly ironic in the way that settlers' names often are — the world itself is not gentle. GJ 107A's primary is an F7V star, warmer than the Sun, and the world settled here sits far enough out in its system that the surface temperature is cool but not frigid, the light slightly blue-white, the ultraviolet loading manageable with modest shielding. What the world has, in extraordinary abundance, is caves.

The cave systems of Tình Yên cover roughly a third of the accessible landmass and descend to depths that have not been fully mapped after three hundred years of habitation. The origin is tectonic: the world is geologically old and its crust is heavily fractured, with a particular limestone-analog stratum that dissolved into vast networks of passages over hundreds of millions of years of mildly acidic groundwater movement. The caves are dry in their upper reaches and humid at depth, and in the humid depths — accessible from the early settlement period, once lighting and breathing equipment improved — something unexpected was living.

The bioluminescent ecology of Tình Yên's deep caves is the system's defining feature. The organisms responsible for the light are primarily a family of slow-growing fungi, not animals — though several cave-adapted invertebrates incorporate the same biochemistry and produce their own light, possibly through symbiosis that predates the settlement by geological time. The fungi grow in colonies on cave walls and ceilings, producing a steady blue-green luminescence that has no apparent circadian rhythm. In the largest cavern systems, travelers have reported walking for hours through what felt like permanent twilight generated entirely by living things.

The Vietnamese-heritage founding community arrived from a corridor segment with existing cave-agriculture traditions — hydroponic and substrate growing in tunnel systems adapted from transit infrastructure — and recognized immediately that the deep cave ecology was both a resource and something that needed careful management. Three hundred years later, the careful management is still ongoing. The Tình Yên cave-cultivation system is a layered use model: upper caves for commercial substrate farming, transition caves for research and monitored harvesting, deep caves under strict ecological reserve rules that have their own enforcement apparatus.

The commercial product is specialty fungi. Tình Yên cultivated varieties — selected over centuries from wild cave strains and adapted for productivity without losing the biochemistry that makes them worth eating — export through Seongho (GJ 660A) to the broader east reach and, for the premium varieties, to inward corridor markets where they are sold under the Suối Tối label (meaning "dark spring," a reference to the cave water sources). The label is recognized across roughly four corridor systems in each direction.

A secondary industry has developed around scientific tourism and research access. The ecological reserve system requires that visitors to the transition and deep caves be accompanied by licensed guides, and the guiding profession has become a respected occupation with its own certification requirements and a waiting list for positions.

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Supply Dependency

Tình Yên is a dead-end system with one aperture connecting to Seongho (GJ 660A), which is both its sole transit link and its primary trade partner. Manufactured goods, technical equipment, and a significant portion of protein foods that the cave cultivation system cannot supply route through Seongho. The fungi export generates sufficient income to maintain a positive trade balance in most years, though the system is sensitive to price fluctuation in the specialty food markets inward.

The single aperture creates a structural vulnerability that Tình Yên's governing council has discussed at length and never resolved, because the resolution — building up sufficient local manufacturing capacity to reduce import dependency — requires capital investment that the fungi export income generates only slowly.

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Faction Notes

The Cave Cultivation Cooperative represents the farming families and operations working the upper and transition cave zones. It is the economic center of the system and the most influential voice in the council's commercial policy. The Cooperative sets the harvest standards that all members must meet, and its certification of Suối Tối product is the mark that commands premium pricing in export markets.

The Ecological Reserve Authority enforces the deep cave access rules and manages the research permit system. Its staff are partly salaried by the council and partly funded by research access fees. The Authority's relationship with the Cooperative is formally cooperative and practically tense, since the Cooperative periodically proposes expansion of the transition zone boundary downward, and the Authority periodically refuses.

The Guides' Circle is the professional association of licensed deep-cave guides. Small in number — under two hundred working guides — but culturally significant. The Circle controls its own certification process and has successfully resisted every attempt by the council and the Authority to transfer that control to a government body.

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Silence Topic

The deep cave mapping effort has been ongoing for three hundred years but is not complete, and the Reserve Authority's internal records contain survey data from a mapping team that entered the deepest accessible cavern network twelve years ago and reported finding a passage section where the bioluminescent ecology was absent — not dead, but simply not present — over a stretch of approximately two kilometers, replaced by bare rock and a faint chemical odor that none of the team could identify. The survey was filed internally, the anomaly was noted, and no follow-up survey has been assigned. The Reserve Authority's director at the time ordered the passage sealed pending further study. It is still sealed.

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Narrative Hook

A research permit application from a university team at Seongho requests access to the sealed passage section, citing new biochemical analysis suggesting the absent-ecology zone may be connected to a unique mineral deposit, and the Reserve Authority's current director discovers that the original sealing order was never logged in the public permit registry — only in an internal file that should have been archived years ago.

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Calibration Note

The READ-ONLY System Profile classifies GJ 107A as F7V, making F-type the correct header designation; the briefing listed M-type and the stub had K-type, both inconsistent with the catalog data. An F7V star is warmer than the Sun with higher UV output, which is reflected in the description of the world as a cool distant body rather than a close-orbiting habitable. Dead_end with 1 aperture and wave_3 settlement produces a community that is genuinely isolated and has had three centuries to develop its own distinct culture and ecological relationship, which the cave cultivation system represents.

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Celestial Bodies

Orbit	ID	Name	Type	Inhabited	Pop	Mass	Gravity	Year (d)	Day (h)	Atmo	Biome	Hydro	Economy	Settlement	Industrial
1	GJ107Ab	—	planet	no	—	terrestrial	0.34g	28	19.2	none	barren	—	—	—	—
2	GJ107Ac	—	planet	no	—	terrestrial	0.62g	105	28.6	none	barren	—	—	—	—
3	GJ107Ad	—	planet	no	—	terrestrial	0.78g	320	33.4	thin	hot_arid	—	—	—	—
4	GJ107Ae	Tình Yên	planet	yes	180K	terrestrial	0.92g	620	27.4	standard	temperate	liquid_water	agricultural	dispersed	specialty_agriculture
5	GJ107A-belt	—	asteroid_belt	no	—	—	—	—	—	—	—	—	—	—	—
6	GJ107Af	—	gas_giant	no	—	—	—	2400	11.4	gas_giant	—	—	—	—	—
↳ 6.1	GJ107Af-m1	—	moon	no	—	dwarf	0.09g	6	148.8	—	frozen	—	—	—	—
7	GJ107Ag	—	planet	no	—	terrestrial	0.44g	5800	36.2	trace	frozen	ice	—	—	—
8	GJ107Ah	—	planet	no	—	terrestrial	0.32g	13000	44.8	trace	frozen	ice	—	—	—
9	GJ107Ai	—	planet	no	—	dwarf	0.11g	28000	26.4	none	frozen	ice	—	—	—
10	GJ107Aj	—	planet	no	—	dwarf	0.10g	52000	22.8	none	frozen	ice	—	—	—
11	GJ107A-oort	—	oort_cloud	no	—	—	—	—	—	—	—	—	—	—	—

Stations & Facilities

ID	Name	Type	Orbits	Population	Economy	Governance	Docking	Gate	Districts
GJ107A-oort-S1	Tình Yên Horizon	horizon	GJ107A-oort	420	transit	—	major	yes	1

Topology

• Hop Distance from Gateway: 7
• Adjacent Systems: GJ 660A