LV-426

'LV-426', also known as 'Acheron', is the name of the fictitious moon (frequently but erroneously referred to as a planet) where the Alien was first encountered by humans in the movie ''Alien'' (1979) of the Alien Series. Some materials related to the franchise refer to it as "LB-426".
LV-426 is a moon in orbit around a gas giant in the Zeta II Reticuli system, which lies beyond the "Outer Rim." LV-426 has .86 Earth gravity and is geologically active, judging from its surface composition (igneous rock, "lava base") and steam vents on its surface. Prior to terraforming, the atmosphere consisted mostly of nitrogen and methane, giving it a strong resemblance to that of Saturn's moon, Titan. The moon was cold enough that carbon dioxide froze putting its temperature somewhere between -182° and -57° C (-296° and -70° F). That is, between the melting points of methane and carbon dioxide. The source materials differ widely on the diameter of this world: figures of 1,200 m, 1,200 km and 12,201 km are given in different sources. Out of these, 12,201 km (from the '') is the only one that is possible given the surface gravity.
In the year 2122, the commercial starship ''Nostromo'', on a return trip to Earth, intercepts an extraterrestrial transmission originating from the moon's surface. The transmission is found to be an acoustical beacon repeating at twelve-second intervals, emanating from a derelict alien spacecraft (the Derelict).
During the 57 years that elapse between the end of ''Alien'' and the events of ''Aliens'', the Weyland-Yutani Corporation are responsible for establishing a colony on LV-426. They make the world habitable with the aid of an enormous, fusion-powered atmosphere processor and established a terraforming colony called "Hadley's Hope."
The colony is destroyed when the atmosphere processor suffers critical damage during military operations, causing a catastrophic explosion which destroys the colony. It is commonly believed by fans that the blast also destroyed the alien derelict, although mathematical and physical considerations cast this belief into serious doubt: apart from the fact that the android Bishop was jokingly guessing at the size of the explosion being "the size of Nebraska" (whereas the actual nuclear fireball seemed considerably smaller), it can be implied from the general direction, in which the colony's Operations Manager Simpson sent the Jorden family on orders from Carter Burke, that the derelict was shielded by the ''Ilium mountain range''. In addition, the Jordens had been driving for already a few days, when they found the derelict. Implying moderate vehicle speed and driving hours, the derelict was in all probability further away from ''Hadley's Hope'' than 350 km (half "the size of Nebraska"), i.e. out of blast range.
According to the computer game ''Aliens versus Predator'', the derelict ship survived the explosion and the Company established a new colony, atmosphere processor, and research facility dedicated to studying the derelict ship and its contents. All were destroyed ten years later during a second alien infestation, when an unnamed Marine disabled the atmosphere processor's cooling systems, causing another explosion.