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 mer". Holst began composing "The Planets" in 1914; the movements appeared not quite in their final sequence; "Mars" was the first to be written, followed by "Venus" and "Jupiter". "Saturn", "Uranus" and "Neptune" were all composed during 1915, and "Mercury" was completed in 1916. Each planet is represented with a distinct character; Dickinson observes that "no planet borrows colour from another". In "Mars", a persistent, uneven rhythmic cell consisting of five beats, combined with trumpet calls and harmonic dissonance provides battle music which Short asserts is unique in its expression of violence and sheer terror, "... Holst's intention being to