The Planets dedication notwithstanding, Imogen Holst "would have been both amused and dismayed by the venture." On 24 August 2006, the International Astronomical Union (IAU) defined what it means to be a "planet" within the Solar System. This definition excluded Pluto as a planet and added it as a member of the new category of "dwarf planets", along with Eris and Ceres. Following the IAU decision, Kenyon D. Wilson composed a trombone quintet piece titled "Songs of Distant Earth". The title comes from Arthur C. Clarke's novel of the same name. The composition contains five movements, each named after one of the
Gustav Holst Guide": "The Planets" (recordings under Boult on HMV and Nixa, and another under Sir Malcolm Sargent on Decca); the "Perfect Fool" ballet music; the "St Paul's Suite"; and three short choral pieces. In the stereo LP and CD eras numerous recordings of "The Planets" were issued, performed by orchestras and conductors from round the world. By the early years of the 21st century most of the major and many of the minor orchestral and choral works had been issued on disc. The 2008 issue of "The Penguin Guide to Recorded Classical Music" contained seven pages of listings of Holst's works