We may no longer believe in the Roman god Pluto, known affectionately as Hades to the Greeks, but the cold world named after him still has so much of an effect on us today.

Now don’t get me wrong. This is February 18th, Pluto Day, not International Save Pluto Day which falls on February 4th. Today we celebrate everything Pluto--but first, a short biography.

Pluto, also called 134340 Pluto, is the second largest dwarf planet in the solar system. It is one fifth the mass of the Earth and also considerably smaller than natural satellites of larger planets, namely moons such as Ganymede, Titan, Callisto, Io, Europa, Triton and our own Moon. It has three moons of its own: Charon, discovered in 1978, Nix and Hydra, both discovered in 2005.
In the same year, the exploration project New Horizons was launched, and it is projected to reach Pluto in 2015, but the latest images have already been sent back to Earth for analysis as recently as last year.

From 1930-2006, it was counted as the ninth planet, and demoted to the status of dwarf planet after a definition of planet was formally decided upon.

Let us then trace the impact of this small icy rock on our culture, through the all too short 76 years it held its highest title.

Pluto, a small world covered with ice, methane, frozen nitrogen and carbon monoxide, was discovered by accident in 1930 by Clyde W. Tombaugh. He had been observing pictures of distant objects beyond Neptune on the insistence of earlier astronomers such as Lowell and noticed an object moving across the sky. This was later credited to a discrepancy in predictions, but it was enough for a deeper investigation. The new planet’s discovery was confirmed by photographs dating back almost 15 years earlier.

But the discovery was not the talk of the town. A name was needed for the new planet. On the historic day of March 24, 1930, there were three contenders, Minerva [the Roman name for Athena], Cronus [the Greek god of Time, known to the Romans as Saturn] and Pluto, which had been suggested by 11 year old schoolgirl Venetia Burney.

It comes as no surprise to us that Pluto had a landslide victory.

The effect on society was near instantaneous. A new Disney character, Mickey Mouse’s pet dog, introduced in 1930, was named Pluto in honour of the planet. Short stories were written, television series made use of the new planet to fuel the success of their stories, the music industry rode upon the boom and most recently, Pluto has been featured in several video games.

A more [or perhaps less] exciting development was the addition of Pluto to the astrological calendar. It was secret source of renewal, or influence on rise and fall of power and corruption, and it coincided with the beginning of the Great Depression, the rise of fascism and Stalinism. When traced back through previous cycles, it was possibly aligned perfectly at the start of the First World War.

The crowning glory came in 1941 when a new element created by Glen T. Seaborg was called plutonium.

In the 1970s, forty years later, the space probes Pioneer 1 and 2 were shown inscribed with the Solar System and Pluto as the ninth planet, with information about it such that alien civilizations would be well informed if they encountered the probes in the future.

Similarly, this information was also carried on Voyager 1 and 2.

But this came to a crunch in 2006 when the International Astronomical Union [IAU] defined the term planet for the first time in history. They concluded with three parameters:
1. The object must be in orbit around the Sun.
2. The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
3. It must have cleared the neighbourhood around its orbit, meaning it must not share its orbit with asteroids.

Pluto failed to fulfill the third condition.

The IAU then classified it in the newly created dwarf planet category.

Since the little planet had been firmly entrenched in popular culture for the best part of a century, there was uproar at the decision. The New Horizons Project declared "the definition stinks, for technical reasons". They have, in fact, backed up their claim, stating that by the new definition, Earth, Mars, Jupiter and Neptune would have to be reclassified, since all of them fail to meet the third condition.

Through it all, there are still mixed feelings about the whole affair. Members of the state assembly in California jokingly denounced the IAU for "scientific heresy". The State of New Mexico declared March 13 as Pluto Planet Day and refused to acknowledge Pluto’s fall from grace. Aesop Rock released the song “Bring Back Pluto” in 2007 on their album None Shall Pass.

Unfortunately for Plutoists worldwide, science is self correcting, even when strong emotion was involved, and after 76 years, had stumbled upon the “right” answer.

Still, in final honour of the planet, the word of the year for 2006 was the neologism “to pluto” means to “demote or devalue someone or something”, the source of this being the Pluto’s plight.

So, the small tiny world at the edge of the solar system continues to haunt our imagination. From the secret communications base described in Douglas Adams’s The Hitchhiker’s Guide to the Galaxy to a real icy planet that the New Horizons Exploration Project has determined, Pluto will remain a source of inspiration and wonder for the years to come.

Let us celebrate this little planet. Happy Pluto Day everybody!