Star System UX-20 is a star system charted by Kitsurugi Uesu during his departure from Central Yamatai. The First Expeditionary Fleet colonized UX-20 I in YE 30.

UX-20 has a dim red star and a lonely, chilly, plant-less planet about twice the size of Earth. There is a Frontier Starport here. In YE 36, the starport became part of the PAINT public transportation system and has a Tenba that regularly visits and provides passenger flights to Shinjuku Starport on Hanako's World.

The Yamatai Star Empire placed a global communications network of Emrys Satellites into orbit of the system's terrestrial world in YE 36.

In YE 41, this star system was conquered by forces from the Interstellar Kingdom Of Kuvexia during the Kuvexian Invasion of YE 41.

• Type M5 V Red Dwarf
• Radius 3.04 x 10⁵ km (0.44 x sol)
• Mass 7.78 x 10²⁹ kg (0.39 x sol)
• Temperature 2600 K
• Luminosity 1.55 x 10²⁵ W (0.04 x sol)

• Type Terrestrial World
• Orbital Radius 2.69 x 10⁷ km (0.18 AU)
• Period 1.06 x 10³ hours (0.12 earth years)
• Physics Large iron/silicate
• Hydrosphere 47 % water, 13 % ice
• Atmosphere Standard breathable
• Biosphere Microbes, fungi

• Type Large iron/silicate
• Radius 7927.31 km (1.24 x earth)
• Surface Area 7.90 x 10⁸ km²
• Land Area 4.26 x 10⁸ km² (2.86 x earth)
• Mass 1.19 x 10²⁵ kg (1.99 x earth)
• Density 5.71 g/cm³ (1.03 x earth)
• Composition 42.8% iron, 28.8% oxygen, 14.8% silicon, 10.6% magnesium, 3.0% other metals, trace other elements

• Gravity 12.59 m/s² (1.29 x earth)
• Escape Velocity 14.13 km/s

• Period 35.44 hours
• Axis Tilt 67.82 °
• Hydrosphere
• Water 47 %
• Ice 13 %

• Type Standard breathable
• Pressure 106.43 kPa (1.05 x earth)
• Composition 73.7% argon, 26.3% oxygen, trace other gases

• Type Cool
• Min Temp 245 K (-27 °C)
• Avg Temp 293 K (19 °C)
• Max Temp 360 K (87 °C)

• Chemistry: Carbon
• Lifeforms: Microbes, fungi