"Cygnus X-1" is a two-part composition by Canadian progressive rock band Rush. The first part, "Book I: The Voyage", is the last song on the A Farewell to Kings album and the second part, "Book II: Hemispheres", is the first song on the following album Hemispheres. Book I clocks in at ten minutes and twenty-five seconds (10:25), and Book II is eighteen minutes and eight seconds (18:08).