Pluto is NOT a Planet!

The search for a planet extremely far away began in 1905. Percival Lowell imagined "Planet X", which was a planet situated in the outer rim of our solar system. Technology in the day was not nearly as good as our current technology, so finding Pluto was not too likely. Lowell died before his "Planet X" was discovered. Pluto was discovered by Clyde Tombaugh in 1930. It was classified as our solar systems ninth planet until a few weeks ago. Pluto's orbit is extremely eccentric; that is, it's not even close to perfectly circular. Since Pluto's orbit is extremely irregular, its surface composition turns from gas to solid as it moves closer or further away from the sun. The surface of Pluto is mainly made up of methane, nitrogen, and carbon monoxide. It is about 1/5^th the size of the earth and it orbits within the Kuiper belt. This belt is the area past Neptune's orbit, and it is home to many small orbiting objects. Pluto is too far away to photograph its surface with today's technology, but its colour is light brown with tinges of yellow. The average temperature of Pluto is around 44 Kelvins, because it is so far away from the sun. Pluto currently has three moons; Charon, Nix, and Hydra. Charon is approximately half the size and mass of Pluto. The other two moons (Nix and Hydra) are about 40 km in diameter. It was proposed that Pluto, and Charon (Pluto's largest moon) were once moons of Neptune, that were knocked out of orbit when Neptune assumed Triton as a moon.

Trans-Neptunian Objects

A TNO is any object in the solar system that orbits past Neptune, in the Kuiper belt. At one point in Pluto's orbit, it is actually closer to the sun than Neptune. Even with this slight intrusion into Neptunes neighbourhood, Pluto can still be called a TNO because it has an

average orbit that is further away than Neptune's. Pluto was closer to the Sun than Neptune between 1979 and 1999.

Comparison Objects

In 2002 and in 2004, Quaoar and Sedna were discovered. Both objects were smaller than Pluto, but they both orbited in the Kuiper belt, and many of the same characteristics that Pluto had. July 29^th, 2005 was the beginning of the end of Pluto's jaunt as a planet; a TNO called Eris was discovered. Eris was slightly larger than Pluto and had a similar surface composition. The group that discovered it, as well as the media first labelled Eris as the 10^th planet. As you can see from this figure above supplied by Wikipedia.org, Pluto is similar to many other TNO's currently not classified as planets. In our system of planets, Pluto is the runt of the litter. It is significantly smaller than all of its brothers, and it's more like a moon than a planet. The International Astronomical Union is the authority for the naming of any object in space, and it is part of the International Council for Science. The IAU had to come up with a redefinition of a planet or else our solar system could end up having hundreds of them.

Why Pluto Should be a Planet

Everyone before the decision date of August 24^th, 2006 grew up knowing that there are 9 planets in our solar system, and Pluto was the 9^th. Every textbook written, taught us that there are

only nine planets; no more or no less. To bring our solar system down to only having 8 planets would be disastrous; all models of our system would have to be remade. Additionally, re-classifying Pluto after so many years being called a planet would not give the IAU a good reputation for sticking to their decisions.

Why Pluto Should not be a Planet

If Pluto were to be kept as a planet, hundreds of other objects in the Kuiper belt would have to be classified as planets as well. Therefore, instead of our solar system having 9, or 10 planets; we could have hundreds. Using the old criteria for classification of planets would actually enable us to call some large asteroids - planets. It is very likely that as technology improves, we will find more and more large objects like Pluto in the Kuiper belt. We will constantly have to add to our existing solar system model, and eventually planet numbers would get to be ridiculous.

IAU Options

The International Astronomical Union had many options to solve the dilemma they faced. The possibilities included: Keeping Pluto classified as a planet and make it the only exception; keeping all other objects similar to Pluto out of planetary status, Keeping Pluto classified as a planet

and include any object similar to it in the planet status, Demote Pluto to some other status - other than a planet; and include other similar objects within that same classification, or Demote Pluto from planetary status and make sure no other objects that will be discovered in the Kuiper belt can be classified as a planet.

IAU Decision

Three conditions to be a planet were created as of August 26th, 2006: The object must be in orbit around the sun, the object must be massive enough to bring itself to be a sphere, and the object must have "cleared the neighbourhood" around its orbit. Under these new conditions, Pluto no longer has planetary status. Since there was such a hullabaloo about loosing Pluto as a planet, the IAU came up with a category to put it in. Pluto is now a "dwarf planet", which has its own set of criteria. To be classified as a Dwarf planet you must: be in orbit around the Sun, have sufficient mass to be a nearly round shape, have not cleared the neighbourhood, and is not a satellite (orbiting another object).

Where Information Came from:

- http://www.space.com/scienceastronomy/050215_pluto_anniv.html

- http://en.wikipedia.org/wiki/Image:EightTNOs.png

- http://www.aerospaceweb.org/question/astronomy/q0270.shtml

- http://en.wikipedia.org/wiki/Pluto

- http://en.wikipedia.org/wiki/Image:TheKuiperBelt_Orbits_Pluto_Polar.svg

- http://nssdc.gsfc.nasa.gov/planetary/factsheet/plutofact.html

- http://www.gps.caltech.edu/~mbrown/eightplanets/