A post from Senator I copied from the T-shirts thread per Uli's request. In this thread we can discuss why Pluto is or isn't a planet. For me, it most definitely is.

Uli, a comment.

You said: "Pluto will always be a planet to me". I'm with you. From the day I was born some 67 years ago (back in the Stone Age), Pluto was a major planet with five known moons and maybe more. In my personal opinion, it always will be, regardless of who might think otherwise. Here is my argument for all to see;

Pluto has a 1,430 mile radius
Mercury has a 1,516 mile radius

There is only a very small difference of an 86 mile radius between the two and yet Mercury is considered a major planet. Why is Mercury considered a major planet and Pluto not? Simply because Mercury is between us and Sol and well within the boundary of the major planets.

Mars has a 2,106 mile radius or 590 miles bigger than Mercury, quite a bit larger. So why is Mercury considered a major planet and Pluto not. Again the answer is simply that Pluto has the misfortune of being the furthest out. Had Pluto been inside the ring of major planets, it too would have remained labeled a major planet. I consider this a very poor excuse for demotion.

A last thought: The word planet means "world that orbits a star". Pluto is a world that orbits Sol.

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rOZZ
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I too, agree that Pluto should be classified as a planet but the radius, in miles, of Pluto is 733 miles. The figures you quoted were the diameter of Pluto and the radius of Mercury.

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.

If you want to consider Pluto to be a planet, then it should be classified as an ICY PLANET along with the other icy planets that we have found and will find that are as big or bigger. This should fit in with the previous designations of:

Rocky planets (Inner)
Gas planets (Outer giants)
Icy planets (Far out dwarfs)

This shouldn't offend anyones' sensibilities and should ease the arguments.

As time and technology move on we will find more and more of the latter. We may even choose to consider members of the Oort cloud to be far out icy asteroids (potential comets)

Perhaps we will find that this pattern exists for other "solar systems"

Oh my word is this still rumbling on???

Some Pluto facts

Pluto (134340 Pluto) is the largest object in the Kuiper belt, the tenth-most-massive known body directly orbiting the Sun; and the second-most-massive known dwarf planet, after Eris. Like other Kuiper belt objects, Pluto is primarily made of rock and ice, and relatively small, about 1/6 the mass of the Moon and 1/3 its volume.

History

Discovered in 1930, Pluto was originally classified as the ninth planet from the Sun. Its status as a major planet fell into question following further study of it and the outer Solar System over the next 75 years. Starting in 1977 with the discovery of the minor planet Chiron, numerous icy objects similar to Pluto with eccentric orbits were found. The most notable of these is the scattered disc object Eris, discovered in 2005, which is 27% more massive than Pluto.

Classification change

The understanding that Pluto is only one of several large icy bodies in the outer Solar System prompted the International Astronomical Union (IAU) to formally define “planet” in 2006. This definition excluded Pluto and reclassified it as a member of the new "dwarf planet" category (and specifically as a plutoid).

Many disagree

Some Astronomers who oppose this decision hold that Pluto should have remained classified as a planet, and that other dwarf planets and even moons should be added to the list of planets along with Pluto.

Basic situation

Anyone over the age of 20 would have grown up being taught that Pluto was the 9th major planet, and astronomers also happily accepted that. However in the 75 years since its discovery science moved on, and more far away Solar System objects were found. In the light of this new evidence it then made sense to re-classify it as a dwarf planet instead of a major planet.

This thread is more a matter of emotion and personal wishes, than scientific fact. OK, so the general public prefer to call it a planet, the IAU and Astronmers choose to call it a dwarf planet, so what. It is still the same lump of whatever it is out there in the same place.

Fortunately, some people are persistent Chris:))

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rOZZ
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Sig line says it all...

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Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

If you want to consider Pluto to be a planet, then it should be classified as an ICY PLANET along with the other icy planets that we have found and will find that are as big or bigger. This should fit in with the previous designations of:

Rocky planets (Inner)
Gas planets (Outer giants)
Icy planets (Far out dwarfs)

This shouldn't offend anyones' sensibilities and should ease the arguments.

As time and technology move on we will find more and more of the latter. We may even choose to consider members of the Oort cloud to be far out icy asteroids (potential comets)

Perhaps we will find that this pattern exists for other "solar systems"

An Icy planet, but still... A Planet.

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rOZZ
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http://en.wikipedia.org/wiki/Kuiper_belt

I personally don't care one way or the other, but the Kuiper belt has over 1000 known objects, and as many as 100,000 total objects. Is size the only parameter that designates Pluto as a planet among 100,000 similar objects? What about Haumea and Makemake?

Steve

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Warning, addicted to SETI crunching!
Crunching as a member of GPU Users Group.
GPUUG Website

An Icy planet, but still... A Planet.

I am quite happy to agree that Pluto is a planet, a Dwarf planet.

An Icy planet, but still... A Planet.

I am quite happy to agree that Pluto is a planet, a Dwarf planet.

Still, it's a Planet.

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rOZZ
Music
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http://en.wikipedia.org/wiki/Kuiper_belt

I personally don't care one way or the other, but the Kuiper belt has over 1000 known objects, and as many as 100,000 total objects. Is size the only parameter that designates Pluto as a planet among 100,000 similar objects? What about Haumea and Makemake?

Steve

Huh, I've learned something new today, "plutinos" and orbital resonance. Interesting, thanks :)

And yes Pluto is a planet :)

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Member of the People Encouraging Niceness In Society club.

A vote for Godzilla, is a vote for cool explosions!

Put it cleanly: prove that Pluto is a solar body & it can be planet again...till then it's a planetoid that Sun collected so long ago! ;)

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non-profit org. Play4Life in Zagreb, Croatia, EU

Pluto is a Planet. Simple:)

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rOZZ
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Put it cleanly: prove that Pluto is a solar body & it can be planet again...till then it's a planetoid that Sun collected so long ago! ;)

I don't understand your question. No one that I know of has argued that Pluto wasn't part of the gaseous cloud that formed into the solar system. It has been here from the beginning of the solar system 4.5 billion years ago. Pluto is what it is regardless of what we call it. By many people's definition it is a planet. By the definition of a small but influential group of astronomers it is what they call a planetoid. When does a pebble become a rock?

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.

If I remember, the plane of Pluto' s orbit is inclined with respect to the orbital plane of the other planets, which derives from a disk. Also, its eccentricity is greater with respect to the other planets.This makes people think that Pluto is a captured asteroid.
Two spacecrafts are now approaching Pluto and Ceres, the biggest known asteroid, discovered by Father Giuseppe Piazzi, a Jesuit astronomer, in 1801. The first is Dawn, approaching Ceres, which should go in orbit around it. The New Horizon spacecraft should reach Pluto on July 14 2015. Maybe we should wait for its analysis of the Pluto environment before deciding about its rank in the Solar System.
Tullio

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Maybe we should wait for its analysis of the Pluto environment before deciding about its rank in the Solar System.

Good point :-)

Pluto could just as easily been smacked during the initial building of the solar system and knocked out of the orbital plane shared by the rest of the planets. Uranus rotates in a retrograde direction and is tipped on it's side. Is it a captured body?

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Bob DeWoody

My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events.

Is it a captured body?

No they are called husbands :-)))

Is it a captured body?

No they are called husbands :-)))

Oi You!

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rOZZ
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Venus is also retrograde, according to Fred Hoyle.
Tullio

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