The series is named after Spica, a binary star system in the constellation Virgo and one of the brightest stars in the nighttime sky. It appears as one star because of the relatively low center-to-center distance between the two component stars, estimated at an average of 11 million miles (17.7 million km). Astronomical observations also suggest that there may be additional stars in the Spica system. In the story, Asumi mentions Spica's distance to Earth as 350 light-years. This figure is also cited by the Japan Aerospace Exploration Agency; however, other sources indicate a distance of approximately 260 light-years.