Sunday, June 29, 2008

Dwarf Planets Are Planets Too

Within the last week, the renewed media focus on Pluto has resulted in encouraging news. More and more people have been commenting on various blogs and web sites expressing opposition to the IAU demotion of Pluto and its general undemocratic decision-making processes.

I am happy to report that as part of the advocacy campaign to inform IAU president Catherine Cesarsky, the IAU, and the media that contrary to Cesarsky's claim, many astronomers and lay people do in fact care a great deal about the designation of Pluto, that Siobhan Elias of Streator, Illinois, has started a new web site,  .  At this site, you can find links to background information on Pluto, the New Horizons mission, Clyde Tombaugh and general astronomy web sites. Siobhan also provides a good summary of what happened at the 2006 IAU General Assembly, links to both professional and lay petitions opposing the new planet definition, and contact emails to Cesarsky, the IAU, CNN, and the BBC. It is important to cc all messages sent to Cesarsky to the IAU, CNN, and BBC to publicly show the overwhelming public support for Pluto.

A huge thank you goes to Siobhan for her hard work and dedication in setting up this very helpful and comprehensive web site.

There is also an excellent interview dated June 23, 2008 with Dr. Alan Stern, Principal Investigator of New Horizons, on the web site of Sky and Telescope. The interview and comments responing to it can be found at . In language that is at the same time compelling and easy to follow, Stern presents the argument why the geophysical definition of planet (namely, the definition that a planet is a non-self luminous object in hydrostatic equilibrium orbiting a star) is by far the most sensible and most useful one, especially in light of ongoing discoveries of a wide variety of planets in other solar systems.

Along with Dr. Stern, I once again urge anyone who shares our view that dwarf planets are planets too and therefore should be redesignated by the IAU as a subclass of planets to, in Stern's words, "get involved" and contact Cesarsky at and cc your message to the IAU at , to CNN at , and to the BBC at . Your message can be as simple as "Dwarf Planets Are Planets Too" in the subject line or, if you so choose, can be more detailed. Feel free to use any ideas from my message to Cesarsky, which appears below:

Dear Dr. Cesarsky, IAU President,

I am writing to express my profound opposition to the 2006 demotion of Pluto from planet status and the subsequent designation of dwarf planets beyond the orbit of Neptune as “plutoids” and to urge the IAU to re-open and reconsider this entire issue.

It is especially disconcerting to me to read comments by you that nobody or very few people, whether scientists or lay people, care about this issue. This claim is simply not true.

As you are well aware, over 300 planetary scientists signed a petition within days of the 2006 vote describing the new planet definition as “sloppy” and stating they will not use it. The lead scientist circulating the petition is Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto and one of the foremost experts in the world on Pluto and the Kuiper Belt.

However, the claim that only scientists connected to New Horizons seek reversal of the 2006 definition is outrageous and untrue. Yes, those in charge of New Horizons focus on study of Pluto and the Kuiper Belt and therefore are more familiar with the particular nuances of this area than most other astronomers. This should give them more, not less credibility with the IAU in a decision on this matter.

The reality is that New Horizons is already fully funded and on its way to Pluto, so there is no issue of compromising the mission by Pluto’s downgrading. And many astronomers not connected with New Horizons, not even American, believe the IAU 2006 planet definition to be irreparably flawed and unusable.

The main problem is the rejection of the concept that dwarf planets are a subclass of planets. If this is reversed, much of the controversy will dissipate. In astronomy, dwarf stars are a subclass of stars, and dwarf galaxies are a subclass of galaxies. What is the problem with keeping the term planet broad with multiple subcategories such as terrestrial planets, gas giants, ice giants, ice dwarfs, super-Earths, etc., with more to come as we discover a wider variety of exoplanets?

This raises another concern, which is that the 2006 definition does not make any provisions for exoplanets whatsoever. That seems quite archaic in an era when these objects are being found on a regular basis.

Also, the concept of an object “clearing its orbit” is vague and could be interpreted to exclude every single planet in our solar system, all of which orbit with asteroids in their orbital fields. It could especially be applied to Neptune, which does not “clear its orbit” of Pluto; for this reason, one could argue the definition sets up a double standard—Neptune is a planet, but Pluto is not even though the orbits of both overlap. And the requirement that an object clear its orbit makes it virtually impossible to have a binary planet system where two objects orbit one another—and also orbit a star—with a common barycenter.

Even if this requirement is changed to state that a planet must “dominate” the neighborhood of its orbit, that is a qualification that never historically has been viewed as necessary for qualifying an object as a planet. It could be kept as a dynamical consideration if we use the most sensible planet definition, which is that a planet is a non-self-luminous spheroidal object orbiting a star and then create a subcategory of dwarf planets that meet this criteria yet do not dominate their orbits. This compromise would give equal value to both dynamical and geophysical considerations and would maintain Pluto, Eris, and Ceres as planets but of the dwarf planet subcategory.

Like many, I am especially troubled by the process the IAU has been using to reach these decisions. Not using electronic voting means that anyone who can’t be in a room on one particular day has no say. In 2006, that left out 96 percent of the IAU’s own membership. The recent “plutoid” classification was made without consulting leading planetary astronomers such as Dr. Mike Brown, Dr. Hal Weaver, Dr. Mark Sykes, Dr. Alan Stern, and many others. How could the IAU craft a definition without seeking input from those who study this subject on a daily basis?

As Stern has pointed out, there are many planetary scientists who are not members of the IAU, meaning they currently have no say in such decisions. I ask that the IAU find a way to include their input, which is of tremendous value here, far more so than that of astronomers who specialize in areas other than planets, such as black holes, quasars, cosmology, etc.

I am a writer, not a professional astronomer, but I love astronomy and see a tremendous opportunity to engage the general public in it during the International Year of Astronomy in 2009. However, I also believe that the credibility of the IAU has been severely compromised by this debacle. Large numbers of both astronomers and lay people feel their voices have been unheard and discounted and are now looking elsewhere for leadership in the field.

For all these reasons, I implore you to recognize publicly that the 2006 definition is a mistake arrived at through a flawed process and to re-open this issue in a manner that is transparent, open and inclusive of all interested parties, makes use of electronic voting, and incorporates the views of planetary scientists who may not be IAU members but have a valid, vital perspective to contribute on this issue.

Laurel Kornfeld
Highland Park, NJ, USA

Finally, to interested readers: Consider attending the Great Planet Debate in Laurel, Maryland, from August 14-16. It's not too late to register! You can find more information about the conference at

Dwarf planets are planets too!

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