The Illinois legislature has way more sense than the International Astronomical Union has shown in two-and-a-half years. It's the IAU who have acted like idiots, with one tiny group forcing a nonsensical planet definition on everyone. The truth is there is NO scientific consensus that Pluto is not a planet. The criterion requiring that a planet "clear the neighborhood of its orbit" is not only controversial; it's so vague as to be meaningless.

Only four percent of the IAU even voted on this, and the vote was driven by internal politics. A small group, most of whom are not planetary scientists, wanted to arbitrarily limit the number of planets to only the largest bodies in the solar system. They held their vote on the last day of a two-week conference with no absentee voting allowed. Their decision was immediately opposed by hundreds of professional astronomers in a formal petition led by Dr. Alan Stern, Principal Investigator of NASA's New Horizons mission to Pluto.

Stern and like-minded scientists favor a broader definition of planet that includes any non-self-luminous spheroidal body orbiting a star. The spherical part is key because when objects become large enough, they are shaped by gravity, which pulls them into a round shape, rather than by chemical bonds. This is true of planets and not of shapeless asteroids and comets. And yes, it does make Ceres, Eris, Haumea, and Makemake planets as well, for a total of 13 planets in our solar system.

Even now, many astronomers and lay people are working to overturn the IAU demotion or are ignoring it altogether. Kudos to the Illinois Senate for standing up to this closed, out of touch organization whose leadership thinks they can just issue a decree and change reality.

As usual, number of paragraphs is inversely proportional to the level of sanity in the post.

Honestly. The Illinois senate? Knows more than a scientific body like the IAU? Yeah, just like they knew more than the rest of us about that daylight savings time thing, too.

Sure thing. Let it go people, Pluto's not a planet. The US is the only place where people give a damn - must be all that Disney.

Wrong, rmgreen. It's not just Americans who care about Pluto, and affinity for Pluto has nothing to do with Disney. I have corresponded online with people all over the world, ranging from parents and kids to amateur and professional astronomers, all of whom believe Pluto is a planet and reject the IAU decision. Pluto supporters are motivated by our love for astronomy and the solar system, not by the Disney dog, in spite of what Neil deGrasse Tyson says.

Pluto IS a planet, and those of us with strong convictions to that effect most certainly will not let this go. Dr. Stern and the many astronomers who agree with him most certainly do know better than the tiny group of the IAU that came up with this preposterous decree. One doesn't need to be a rocket scientist to know that a definition that states that a dwarf planet is not a planet at all, which is inconsistent with the use of the term "dwarf" in astronomy, where dwarf stars are still stars, and dwarf galaxies are still galaxies, makes no sense. Neither does it make sense to define objects solely by where they are while ignoring what they are. That is what the IAU definition does. If Earth were in Pluto's orbit, according to the IAU definition, it would not be a planet either. A definition that takes the same object and makes it a planet in one location and not a planet in another is essentially useless.

I recommend you visit the site of the Great Planet Debate, held at the Johns Hopkins University Applied Physics Lab in Laurel, MD in August 2008 and listen to the audio proceedings of the conference. There you will hear intelligent, thoughtful discussion of both sides of the issue. The site is located at http://gpd.jhuapl.edu/

wow. with all that useless banter, it just makes me happy that there are real scientists out there doing real research, because these folks obviously aren't. Makes me wonder what's in it for you to be such a huge distraction from real science.

Get over it people. Pluto is a planet. What knuckle head got the idea that it shouldn't be,... Probably some student who needed a topic for their PhD.... Or some wannabe fringe scientist looking to make a name for themselves. This one goes down in the history books as the stupidest debates. First it's a dwarf planet... and now it's a "plutoid"??? Common!

if Pluto is a planet, does that mean Make-Make, Quaoar, Eris (which is large than pluto), Haumea, Orcus, Eris, Sedna, Veruna, Ixion, and Huya are also planets. In the early 1800s, Ceres, Pallus, Juno and Vesta were considered planets, and listed as such in text books. In the late 1800s that stopped, because they were finding more and more asteroids...and realized that they were just the first asteroids discovered. Should we go back and call them planets AGAIN, as well?

those who do not learn from the past...

Why do new discoveries and the realization that past discoveries and classifications of such discoveries may ned to be revised bother people so much? Do you want to start calling dolphins fish again because they were, at one time, classified that way?

If Illinoisans want to call Pluto a planet, why stop them? Being from Illinois, I was excited to hear that Pluto's planetary status had been re-established. For those who are unproportionately angry that Illinois dare waste time to decide such an issue....get a life. Unless you live in Illinois, the decision will not effect you. Ranting about the decision makes it seem as though you are the unintelligent one. Odds are that "real scientists" [Excuse the lame use of blanket terminology,I wanted to point out the absurdity of the original statement] probably won't be distracted by a senatorial decision that carries no real threat to global scientific standards. America is still holding on to the inch...I say let Illinois have their Pluto and classify it, too! Besides, with the recent election of Barack Obama and the Oscar win by Slumdog Millionare for best picture, shouldn't we be rooting for the Underdog anyway? [Ha! A Disney reference!]

Like Clyde Tombaugh, I grew up in Illinois, though I went east instead of west to be come an astronomer. I have worked with astronomers on both sides of the "Pluto is a planet" issue, and currently work with people who are looking for planets around other stars. It is clear that Pluto is not the same kind of planet as the Earth, Venus, Mercury, and Mars. It is also clear that there are other objects like it in the Kuiper Belt. If we saw an object like Pluto around another star, and it was the only one we saw, we might call it a planet. If we saw other objects like it in similar orbits, we would call it a giant asteroid or a dwarf planet. We should treat objects in our solar system the same way.

Ms. Kornfeld is well-versed in this topic and I hope you will heed her words. Earth is a planet. If Earth was in Pluto's orbit, according the new IAU definition of a planet that was deceitfully passed by 424 of 10,000 IAU members in Prague in 2006 on the last day of the conference when most people had left, thinking Pluto's status was secure, it would not be considered a planet. Doesn't that make an impression on you? I think having 13 planets is fine. Ms. Kornfeld's definition of a planet is far more scientific that the current one. Hopefully the August IAU meeting in Rio this year will address the glaring faults of the Prague plop and come up with a sound definition with a proper vetting and a quorum of members voting on it.

The IAU has left us with more confusion, ambiguity and vagueness than before they started. Their definition of a planet cannot apply to other solar systems either. Are dwarf galaxies not galaxies? Are dwarf stars not stars? Are dwarf human beings not people? How can a dwarf planet not be a planet? Pluto is definitely a Kuiper Belt Object (KBO) because of its composition, orbital eccentricity and inclination along with its small size. If it were brought close enough to the sun such as where the earth is, it would have a long tail like a comet just as one would expect from a KBO. To create a new category just based on size unnecessarily confuses the issue. The only real discussion should be whether Pluto could be considered to be BOTH a KBO AND a planet simultaneously. After all isn't Australia a giant island, country and continent all at the same time? I hope the IAU comes to its senses this August in Rio and throws out the dwarf planet category and gives us a sensible and usable definition of a planet.

You guys are the absolute laughing stock of anyone who considers themselves even an Amateur Astronomer.

Astronomy changes as we grow to better know our universe. That's the way it works. Pluto is a tiny little body that was only called a planet originally due to a misunderstanding of it's size.

Had the original discoverers known how big it really was, it would never have been classed as a planet in the first place.

Any definition that allows pluto to remain a planet is going to have to allow other bodies, such as Eris, to become planets as well. This is quite useless.

Being a planet or not being a planet is simply a name anyway. It's a classification. The lack of it's planet designation will not stop people from looking for it in the sky, it wont stop scientists from studying it's binary nature with it's moon.

What are you all affraid of?