MAKE PLUTO A PLANET AGAIN! (CHANGE IAU DEFINITION OF A PLANET.)

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The demotion of Pluto from 'planet' to 'dwarf planet' status was devastating for people around the world, especially school children who seemed to have a personal connection with Pluto as their favourite planet.

It doesn't make sense to call Pluto anything other than a planet, given that it has a diameter of almost 2,400 km and it actually has five moons that orbit around it.

Let's convince the International Astronomical Union (IAU) to redefine the term 'planet' so that once again, Pluto can be called a planet!

Here is the official request to the IAU: Please change your definition of a planet from the current definition:

A planet is a celestial body which:

1. is in orbit around the Sun,
2. has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
3. has "cleared the neighborhood" around its orbit.

To this new definition:

A planet is a celestial body which:

1. is in orbit around a star,
2. has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
3. has "cleared the neighborhood" around its orbit OR has a diameter that is greater than 1/2 that of Earth (6,371 km) OR has a diameter that is greater than 1/6 that of Earth (2,124 km) and has at least two moons orbiting it.

1. The recommended change in section 1 from "Sun" to "star" reflects the fact that thousands of planets have recently been discovered orbiting around other stars, not just our Sun.

2. No change is required to section 2.

3. More flexibility is required in section 3.

Part A requiring a "clearing of its neighbourhood" should remain as it is, but we should add two additional conditions that could be met in lieu of "clearing its neighbourhood."

Part B stipulates that we should call any object that has at least half the diameter of Earth a planet. The reason for this is the fact that we are currently searching for planets in the Kuiper Belt and the Oort Cloud, but, by definition, even if we were to find a planet there that was ten times the size of Earth, we would not be able to call it a planet because it has not "cleared its neighbourhood." Based on the current IAU definition, we would have to call it a dwarf planet which does not make any sense at all.

Part C is the addition of the "Pluto Clause." Pluto is quite different from all of the other dwarf planets because of its large size and the fact that it has five moons orbiting around it. Pluto clearly meets this new definition of a planet since it has a diameter greater than 1/6 that of Earth and it has at least two moons.

Mr. Benvenuti, we respectfully request that you forward this request to the appropriate decision makers at the International Astronomical Union and that you accept this new definition of a planet.

Tom Vassos



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