Complex sentence: The radiation from the nuclear explosion leaves behind an identifiable signature that is discovered by a Cylon patrol one light-year away, one year after the destruction of the ship, and leads a Cylon invasion force to New Caprica.
Split into simpler sentences: The radiation from the nuclear explosion left behind an identifiable signature that was discovered by a Cylon patrol one light-year away. One year after the destruction of the ship, it led a Cylon invasion force to New Caprica.