Gagarin Station is the largest deep space station built by humanity, a Bernal Sphere design with a 500-meter-diameter habitable area. It was constructed beyond Pluto, nearly 80 Astronomical Units (12 billion kilometers) from Sol. Moving crew and material to this location bankrupted most of the backers.
Gagarin was placed at the inner edge of the heliopause -- the point at which the solar wind can no longer push back the interstellar medium. It was built to test a number of faster-than-light drive principles that theoretically could only occur in interstellar space. The station was nicknamed "Jump Zero," as it was intended to be the jumping-off point for humanity's expansion into the galaxy. Shortly after the station was completed, the Prothean ruins were discovered on Mars, rendering the entire effort moot.
After struggling to make a profit for a decade, Gagarin was sold to the Systems Alliance in 2159 for a fraction of its construction costs. The Alliance refurbished it as a research and training center for the recently discovered biotic phenomenon.
In 2169, the Biotic Acclimation and Training program was shut down and Gagarin became a general research facility. Its remote location and intentional isolation from the extranet makes it popular for dangerous research, particularly in the field of artificial intelligence. Humanity's first stable AI, the Alliance-sponsored "Eliza," achieved sapience at Gagarin in 2172.
Today, Gagarin Station has a permanent population of approximately 9000. A plan has been proposed to move it to the gravitationally stable barycenter point between Pluto and the Charon Relay, allowing it to serve as a gateway facility between the Sol and Arcturus systems. The high cost of safely moving its mass has delayed this indefinitely.