Pluto is a planet which usually orbits further than the orbit of Neptune. It is very small – smaller than any of the ‘official’ planets and is currently classified as a “dwarf planet”. Pluto is even smaller than seven of the solar system’s moons (the Moon, Io, Europa, Ganymede, Callisto, Titan and Triton). American astronomer Pervical Lowell was the man who first got the hints of Pluto’s existence in 1905 from odd deviations he observed in the orbits of Neptune and Uranus, signifying that an additional world’s gravity was tugging at them from outside. He estimated its location in 1915, however died without finding it. Planet Pluto’s discovery came in 1930 from Clyde Tombaugh at the Lowell Observatory, derived from predictions by Lowell and other astronomers.

Pluto was the single planet to be named by a kid. Pluto was named by an 11-year-old girl, Venetia Burney of Oxford, England, who suggested to her grandfather that this new planet needed to be named after the Roman god of the underworld. Her grandfather then suggested the name on to Lowell Observatory. The name Pluto also tributes Percival Lowell, whose initials are the first two letters of Pluto.

Pluto is about two-thirds smaller than Earth’s moon. Since it is too small, many scientists don’t consider it a planet at all. In 1999, a group of scientists tried to re-classify Pluto as a comet. However, on August 24, 2006, Pluto’s status was officially altered from planet to dwarf planet.

Pluto has not yet been visited by a spacecraft. Hubble Space Telescope was able to resolve only the largest features on its surface for scientists to study. Very little is known about Pluto and its moons as it is so far away. A spacecraft known as New Horizons was launched in January 2006 and if all goes right way it should reach Pluto in 2015.

Pluto’s Moons

Pluto has 3 moons. In 1978, astronomers discovered Pluto had a very large moon which is almost half its size called Charon, which named for the mythological demon who ferried souls to the underworld in Greek mythology. The huge size of satellite Charon sometimes leads scientists to mention Pluto and Charon as a double dwarf planet or binary system. These two are just 12,200 miles away from each other. Charon takes 6.4 Earth days to orbit around Pluto and one Pluto rotation, or a Pluto day, also takes 6.4 Earth days. Due to this Charon hovers over the same spot on Pluto’s surface and the same side of Charon forever faces the Planet Pluto. This phenomenon is also known as tidal locking.

In 2005, scientists discovered two other small moons of Pluto, and called them Nix and Hydra. These are two to three times farther away from Pluto than Charon, and are considered to be just 31 to 62 miles wide.

Formation of Pluto

The theory behind the formation of Pluto and Charon assumes that a nascent Pluto was hit with a glancing blow by another Pluto-sized object. The majority of the combined matter became Pluto, whereas the rest spun off to develop into Charon.

Pluto’s Atmosphere

Pluto’s atmosphere comprises of a thin layer of nitrogen, methane and carbon monoxide gases. Pluto’s elongated orbit is expected to have a most important effect on its atmosphere. When Pluto is away from the Sun, its atmosphere should gradually freeze out and fall to the ground. When Pluto is nearer to the Sun, the temperature of Pluto’s solid surface raises, causing the ices to sublimate into gas. Scientists using the Submillimeter Array have discovered that Pluto’s temperature is roughly about 43 K (−230 °C). In October 2006, scientists declared the spectroscopic discovery of ethane on Pluto’s surface. This ethane is formed from the photolysis of frozen methane on Pluto’s surface and suspended in its atmosphere.

Pluto’s Orbit and Rotation

Pluto’s orbital period is 248 Earth years. Unlike rest of planets, Pluto revolves around the Sun in an orbit which is not circular but is an oval or egg shape. Due to this, Pluto will orbit within of Neptune’s orbit. At times because of this Pluto comes nearer to the Sun than Neptune. In addition, Pluto’s orbit does not lie flat in the same plane like the rest of the planets. Pluto’s orbit is tilted as a result it orbits above and below the other planets’ orbits in our Solar System.

Pluto is very small; and because of its small size it is very sensitive to immeasurably small details of the solar system. Therefore it is really difficult to forecast factors that will gradually disrupt its orbit.  Pluto’s orbit itself is stable, but its position on that orbit is not stable and hard to predict. Pluto’s orbit is kept stable and safe from planetary collision or scattering by several resonances and other dynamical effects.

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[Image - www.nasa.org]

Poor old Pluto, for billions of years it lay unnoticed, out there on it’s own, not bothering anyone, content to spin around by it’s lonesome. Then in 1930, the Lowell Observatory in Flagstaff, Arizona declared it as a planet. And so Pluto became Pluto, up until then happily anonymous; it was christened by an eleven year old Oxford schoolgirl, Venetia Burney, calling it Pluto, the Roman god of the underworld who was able to make himself invisible.

Pluto was now a famous planet, recognisable to school-children – but what a strange planet it was – it was tiny, only coming in at one hundredth the size of earth and is primarily constituted of nitrogen ice – so it is a great chunk of ice, floating out there on its own. Sitting on Pluto, our mighty sun would be simply just another small star amongst the may others. It’s orbit of the sun is equally bizarre, unlike every other planet, it does not orbit the sun like all the other planets – circularly but rather elliptically.

Horribly, towards the end of the twentieth century, this odd, little planet was considered perhaps to odd and debate raged as to whether it was a planet at all. The Kuiper belt was discovered in 1992 – similar to an asteroid belt but constituted by frozen ices such as methane, ammonia and water. In this Kuiper belt were discovered many objects similar to Pluto, and so if Pluto was allowed into the Planet Club, these others would too and that would never do. So on 24 August, 2006 the International Astronomical Union defined the term ’planet’ for the first time and surprise, surprise Pluto didn’t make the grade. So as soon as it was promoted to a planet it was demoted, fickle humans eh?

[image] – www.nasa.gov

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