System Specs:
- Stellar Mass: 0.83 Sol Masses
- Stellar Class: G
- Luminosity: N/A Sol
- Planets: 1
- Moons: ≥ 1
- Asteroid Belts: 0
- Asteroids: 0
- Objects: 1
Thorne would have been a binary system if brown dwarf Mnemosyne ignited into a star.
Mnemosyne’s moon Lethe lacks heavy metals, but contains rich amounts of resources for the Normandy SR-2’s needs. The brown dwarf itself has a Derelict Reaper in a precarious orbit.
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Planets Directory:
- Mnemosyne
- (Lethe)
- Derelict Reaper
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Mnemosyne:
- Orbital Distance: 0.81 AU
- Orbital Period: 0.8 Earth-years
- Keplerian Ratio: 0.83
- Radius: 72,541 km
- Day Length: 18.7 Earth-hours
- Atmospheric Pressure: N/A atm
- Surface Temp: 1,500 °C
- Surface Gravity: N/A g
- Mass: 37 Jupiter-masses
- Satellites: ≥ 1
Mnemosyne is a brown dwarf of approximately 37 Jupiter-masses. It is young enough that some nuclear fusion still occurs within its depths. It is luminous, and radiates more heat than it receives from the star Thorne, with an atmospheric temperature in excess of 1,800 degrees Kelvin (1,500 degrees Celsius).
Early probes of Thorne showed evidence of a minor gravitic anomaly in the northern hemisphere. This area of unexpectedly low mass did not move with the prevailing wind patterns. While an investigation was planned by the Besaral Institute of Planetary Science, the school ultimately sent an expedition to study the famed “deep anomalies” of the gas giant Ploba instead.
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Lethe:
- Orbital Distance: 2,323,500 km (from Mnemosyne)
- Orbital Period: 16.4 Earth-years
- Keplerian Ratio: N/A
- Radius: 5,663 km
- Day Length: 16.4 Earth-hours
- Atmospheric Pressure: 0.58 atm
- Surface Temp: 31 °C
- Surface Gravity: 0.59 g
- Mass: 0.462 Earth-Masses
Lethe is the largest moon of Mnemosyne, massive enough to retain its own thin atmosphere of methane and nitrogen, and heated by the brown dwarf to relatively moderate temperatures. While nearly the size of Earth, its overall density is low, suggesting a paucity of valuable heavy metals. It is tidally locked to Mnemosyne, one hemisphere always bathed in the brown dwarf’s heat and dim red light.
The moon experiences constant weak tectonic activity, driven by the tidal fluxes of Mnemosyne’s gravity rather than Lethe’s own internal heat. Several large, ancient volcanoes release wide-ranging flows of molten silicate.
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Derelict Reaper:
Orbiting Mnemosyne is a two-kilometer-long ship with the unmistakable profile of a Reaper. It is giving off power signatures in localized areas, but they are far weaker than a ship this size would indicate. The Reaper seems to maintain a mass effect field that has kept it from falling into the failed star, but massive holes have been blasted and melted into parts of the hull and remain unrepaired. The only logical conclusion is that the Reaper “died” or was at least reduced to minimal functioning a long time ago.
Mission
Main article: Reaper IFF
At some point, Cerberus discovered the Derelict Reaper and dispatched a research team led by a Dr. Chandana to study it. It is believed that 37 million years ago, an unknown spacefaring race fired a mass accelerator round of incredible speed and power at the Reaper, which hit and disabled it. The round continued moving, eventually impacting the planet Klendagon and creating the Great Rift Valley there. This Reaper’s death was likely the unknown race’s last act of defiance before their imposed extinction. Despite the massive damage the Reaper sustained, the mechanism responsible for indoctrination was still active. The Cerberus team unwittingly succumbed to the indoctrination and were converted into husks.
The Illusive Man sends Commander Shepard to the Reaper to investigate why Dr. Chandana’s team has ceased communication and to search for the Reaper’s Identify Friend/Foe tag, which would allow the Normandy to safely utilize the Omega 4 Relay. When Shepard’s squad boards the Reaper, the ship’s kinetic barriers engage, trapping them aboard. The barriers can only be disengaged by destroying the ship’s core, which will also disengage the mass effect field keeping the Reaper from falling into Mnemosyne’s gravity well. Fighting through the husks made from the Cerberus team, Shepard acquires the IFF and reaches the core. There, the squad encounters a lone geth, who is incapacitated by a wave of attacking husks. Shepard destroys the Reaper’s core and escapes with the inactive geth to the Normandy just before the Reaper is destroyed by Mnemosyne’s atmosphere.
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