Between 1979 and 1989 Jupiter, Saturn, Uranus and Neptune were aligned in such a way that the space probe Voyager 2 was able to visit each one in turn. Pluto, at that time the ninth planet in our solar system, missed out on this interstellar rendezvous.
In 1929 the young American astronomer Clyde Tombaugh was given the task of systematically imaging the night sky in the direction of Uranus and Neptune. Astronomers conjectured that an unknown planet was influencing the orbit of Uranus. Tombaugh had to compare pairs of photographs to see if any objects had shifted position. On 18 February 1930, he found a moving object and, following scientific corroboration, the news was made public on 13 March 1930.
The planet was named Pluto after the god of the underworld. The name was suggested by Venetia Burney, an eleven-year-old schoolgirl living in Oxford, England, who was interested in classical mythology and whose grandfather proposed the name to colleagues at the Lowell Observatory in Arizona.
In 2008, Pluto was demoted to the status of a “dwarf planet” – a spherical celestial body revolving about the sun, similar to a planet but not large enough to gravitationally clear its orbital path of most or all other celestial bodies. Pluto has one moon named Charon and four satellite bodies: Styx, Nix, Kerberos, and Hydra. Even though the surface of Pluto is a frigid minus 230C, geophysical models suggest there could be a warm ocean concealed beneath that produces a wispy nitrogen-rich atmosphere, depending on where Pluto is in its orbit around the Sun.
The English composer Gustav Holst might have included Pluto in his orchestral suite “The Planets”, except that it was completed in 1918. Pluto was discovered four years before Holst’s death, but the composer had no interest in extending a work which, despite its enduring popularity, he had long ago set aside. So, until recently “The Planets” kept its original seven movements:
Mars, the Bringer of War
Venus, the Bringer of Peace
Mercury, the Winged Messenger
Jupiter, the Bringer of Jollity
Saturn, the Bringer of Old Age
Uranus, the Magician
Neptune, the Mystic
Eventually, the Hallé Orchestra commissioned the English composer Colin Matthews to write a movement dedicated to Pluto. Matthews based it on solar wind, the plasma stream regularly released by the Sun. Named “Pluto, the Renewer” and posthumously dedicated to Holst’s daughter Imogen, it was first performed in Manchester, England, on 11 May 2000.
Pluto cannot be seen with the naked eye, but it has been photographed by the Hubble Space Telescope and the New Horizons probe, which is doing a flyby on 14 July 2015. New Horizons (carrying a compact disc with the names of 434, 738 people – including the writer of this blog) is expected to send data across 3.6 million miles to waiting scientists whose interest has shifted from Martians to the newcomer on the block. Pluto is back in the planetary limelight and revenge is sweet!