C/2012 S1 (ISON) is a comet headed into the inner solar system for the first time. Coming from trillions of miles away to make a parabolic orbit around the Sun, accelerating to ~500,000mph, it could be the most spectacular in modern history. This song tributes it. It starts off with its dark, lonely, dusty origins, to the chaos of the Sun pulling it in and it raging into the inner solar system (represented by some chaotic American dubstep-styling), to the majestic beauty of the sight of it on Earth (with soaring strings and piano underpinned by the bassline from before but now moving in chords).
Slightly dubstep-inspired, named for the closest star to the supermassive black hole at the center of the galaxy (S2). The star is a young star and the fastest-moving massive object in the galaxy, and by metaphor, the song expresses the hubris and beauty of youth.