The International Astronomical Union has voted to demote Pluto from full planetary status, but as a planetary scientist, I know that reclassifying Pluto as a dwarf planet will not make any difference scientifically — we will still study it.

But humans are resistant to change. Most of us grew up learning that our solar system contains nine planets, and we are upset by this change. Because Pluto was discovered at Lowell Observatory, Flagstaff residents definitely have a vested interest in this little world.

One benefit arising from this controversy is the enhanced awareness that science is not static. I first realized this in fifth grade when I learned about the discovery of Saturn's moon Janus. Janus was the first new moon discovered in 15 years, the first new moon in the lifetime of that fifth-grader. That was when I realized that science is not just a bunch of facts discovered long ago. Science changes as new information is obtained through technological advances.

Planets originally were defined as objects moving relative to the stationary background stars. That definition no longer fits the diversity of objects comprising our solar system. We need a definition based on physics. We need to keep it simple. That is why I liked the definition proposed by the planet definition committee appointed by the IAU: A planet orbits a star and has sufficient mass so its gravity has pulled it into a sphere. It is short, simple and comprehensible.

We could then subdivide planets into terrestrial, giant and perhaps dwarf planets. We teachers would not force students to learn the names of all the planets, especially once the count reached more than about 15. Instead we would focus on the physical characteristics that set the planetary subgroups apart: composition, size, rotation rate, etc.

Memorizing the names of the planets is not science. Science involves understanding planetary similarities and differences and what they imply about the solar system's evolution.

The planet definition committee, which included planetary scientists, astronomy historians and science writers, originally proposed a definition which would have made Pluto-Charon a double planet and given us at least a 12-planet solar system.

Before forming the committee, the IAU requested input on possible members from the American Astronomical Society's Division for Planetary Sciences, the largest international organization of planetary scientists. Many members of the final committee were on the list submitted by Division for Planetary Sciences' Executive Committee.

The planet definition committee spent months working on this issue and did a very thorough job, drawing upon community input to develop their recommendation. The rejection of their proposed definition by those attending the IAU General Assembly in Prague is an insult to the committee's hard work.

The resolution to bestow planetary status upon only eight objects was hastily thrown together in one week during the meeting. Those voting on the resolution to demote Pluto represented only 5 percent of the entire IAU membership, and planetary scientists comprised about 10 percent of those voting. Why the small turnout? Only those in attendance in Prague could vote. Most of us could not attend the meeting because we lacked travel funds and/or had academic commitments.

That is what bothers me about this vote. Planetary scientists, not cosmologists studying distant galaxies, should have the majority input into the criteria for defining a planet and it should be their vote that prevails. I would accept a new definition of what constitutes a planet if it had been discussed and approved by the planetary community.

Changing the designation of a planet is not unprecedented in the history of astronomy: Ceres joined the planetary ranks when it was discovered in 1801, but with the discovery of additional small objects orbiting between Mars and Jupiter, it was later relegated to the title of largest asteroid.

However, now we are confronted with a convoluted definition that requires that a planet not only orbit the sun and is spherical but must also gravitationally clear its orbital neighborhood of debris. "Neighborhood" is not defined in the approved resolution. How far out does it extend? Does "debris" include non-natural debris, such as spacecraft? If so, then the Earth may not qualify as a planet. I know many NAU students in my Introductory Astronomy class will have trouble understanding this definition. I really feel sorry for elementary school teachers who have to explain this to their students.

We need a good definition for a planet. The IAU-approved resolution is not it.

Nadine Barlow is an associate professor in Northern Arizona University's Department of Physics and Astronomy. She is a planetary scientist whose research focuses on impact cratering and is a member of the Division for Planetary Sciences Executive Committee.

A planet always

The following editorial appeared in Saturday's Washington Post:

To all the astronomers who voted in Prague this week to demote our solar system's smallest planet to the status of "dwarf planet" we ask: What do you know? Ask any third-grader how many planets there are. Nine. Ask whether Pluto is one of them. Of course it is. Ask them whether they care how a bunch of telescope jockeys voted. Of course they don't. So there.

And we're with them — standing firmly behind Pluto's status as a planet. Yes, yes, other bodies orbiting the sun have as much claim scientifically to full planethood as Pluto. And we can't have this exclusive club getting too big, can we? But still, there's such a thing as tradition. And it's just not right to teach generations of kids that there are nine planets, only then to take one away. Sure, it would be inconsistent to keep Pluto as a planet even as astronomers discover other big rocks out there in space. But, as Emerson might have put it, a foolish consistency is the hobgoblin of astronomers.

Pluto's demotion sensible

From the Cincinnati Enquirer, on the controversy over Pluto:

If Pluto hadn't been a planet, what would have Mickey named his dog?

This is just one of several cosmic questions that comes to mind in the debate over whether Pluto is our solar system's ninth and most distant planet from the sun or just a cold little rock spinning aimlessly through space. …

Pluto, named for the Roman god of the underworld, differs from the eight inner planets … in that it is a lot smaller and has an orbit more elliptical than circular. … It's even smaller than originally thought, and there are a lot of other pieces of rock and ice out in that part of the solar system, known as the Kuiper Belt, including some that are bigger than Pluto. …

It would be ridiculous not to reclassify the planets based on the most up-to-date knowledge.

As to whether today's science would have caused Mickey Mouse to rename his dog — to even consider such a thing is Goofy.

5 things that, like Pluto, need a downgrade//

From the The Washington Post:

Last week, the International Astronomical Union stripped Pluto of its official status as a planet. Here are five other things we'd really like to see demoted.

1. "Godfather III." This "film" is just not worthy of "Godfather" status.

2. Gluttony. If it remains a deadly sin, a lot of us are in trouble.

3. Tour de France/100 yard dash. Not a sport if winners keep getting busted for 'roids.

4. Segways. Try walking, pal.

5. Tom Cruise. Downgrade to a B-list actor … oh wait, already done. Thanks, Paramount.

When one cosmic door closes …

From The Washington Post:

On Thursday, scientists made it official: Pluto doesn't measure up. It has been stripped of its "classical" planetary status and demoted to "dwarf" planet, or planette. But surely being kicked out of the Cosmos Club won't spell the end for our little neighbor 2.7 billion miles from Earth. Herewith, some suggestions of future roles for Pluto:

Hacky Sack.

Setting for new Discovery Channel documentary, "Starbucks: The Unconquered Territory."

Off-off-offshore tax haven.

Rest area (no vending machines).

Learn to accept self as useless giant snowball of methane, water and rock. And be the best darn methane-water-rock snowball you can be!