Monday, March 23, 2009

Sorry, Mike Brown, but the Debate Is Not Settled

Sorry, Mike Brown, but the debate over Pluto’s status and what defines a planet is not settled.

In response to Illinois’ proud proclamation of March 13 as “Pluto Day,” Dr. Mike Brown, discoverer of Eris and in his own mind, the person who “put the solar system in order by killing Pluto” claims in a National Geographic article of March 11, 2009 that the planet debate is “settled,” that there is no longer “ a vigorous debate” going on about planet definition, and that only a handful of scientists continue to lobby for Pluto’s reinstatement while the rest of astronomers have “moved on.”

Brown even goes so far as to condemn the Illinois resolution as “dangerous to public understanding of science.”

Talk about denial.

At the Isaac Asimov Memorial Debate, held at the American Museum of Natural History on March 10, 2009, a panel of six planetary scientists moderated by Dr. Neil deGrasse Tyson made it abundantly clear that the issue of what constitutes a planet is far from settled--both at the lower end with small objects like Ceres and Pluto and at the upper end with brown dwarfs and sub-brown dwarfs that straddle the boundary between planets and stars.

Even dynamicists like Dr. Steve Soter and Dr. Jack Lissauer, who support defining only the eight gravitationally dominant objects in our solar system as planets, expressed dissatisfaction with the IAU definition and its vague wording requiring a planet to “clear the neighborhood of its orbit.”

“Now about clearing, that was an unfortunate term, because planets never fully clear their orbits,” Soter said.
Even Tyson departed from his usual “I killed Pluto” stance, admitting that “perhaps planetary science is still in its infancy and has no business classifying anything at all yet.”

Tyson should probably stop titling his lectures “How I Killed Pluto, and Why Pluto Had It Coming.” As glib as he is, he can certainly come up with a better titled that more accurately portrays his discussion and does justice to this issue. Leave silly titles like that to Brown.

With an audience of about 1,000 people seven astronomers who disagree on whether or not Pluto should be included as a planet all expressed dissatisfaction with the IAU definition, which Brown still claims “settled” the debate.

This was the third debate on planet definition that I attended personally. The first was in Brookline, MA, in February 2007, sponsored by the Clay Observatory. The second was, of course, the two-and-a-half day Great Planet Debate in August 2008 at the Johns Hopkins University Applied Physics Laboratory in Laurel, MD.

Notably, Brown did not attend or participate in any of these events.

Every one of these public debates was congenial and friendly. Professional astronomers showed that they could disagree with one another and still laugh together and be entertaining. In each case, public input was welcomed and valued. In each case, presenters provided in depth discussion of the many nuances and factors going into the debate--how planets were formed, planetary migration, what we learn from exoplanets, the low and high end of planet definition, concepts such as gravitational dominance and hydrostatic equilibrium, and more.

In other words, in each case, the public was presented with the complexity of the issues involved, which all illustrate that what is needed most is time and deliberation, not a quick rush to a “solution,” as was done by the IAU in 2006.

Therefore, every one of these debates can be said to have successfully addressed this issue in a way that the IAU did not.
Yet Brown, who seems to get some strange pleasure out of repeatedly talking about nails and coffins in relation to Pluto, bases his claim that the debate is “settled” on this rushed, political IAU decision, in spite of the ongoing planet definition debates, including those held by the American and European Geophysical Unions, that continue to be held to this day.

It sure sounds a lot like denial to me--either that or some personal need by Brown to view himself as the one who put the solar system in order--a description that maybe could be applied to Nicholas Copernicus, Galileo, Johannes Kepler, or Isaac Newton, each of whom outlined a then-new set of principles about the organization of the solar system--if to anyone at all.

In addition to Brown’s having been for Pluto and Eris being labeled as planets before being against it, he intersperses discussion of his personal shaping of the solar system with strange comments about his family that contribute nothing to the rich discussion of what makes a planet and revolve more around himself than around planetary science.

One of the stories he loves to tell is how, on the night he discovered Eris, which he then considered the tenth planet, he phoned his pregnant wife to tell her the exciting news. Her response? According to Brown, it was “oh, that’s nice. Could you remember to pick up milk on the way home?”

Pick up milk?! Now imagine an actor who just won an Oscar or a politician who just won an election calling his or her spouse with the ecstatic news, only to have that spouse respond with, “remember to bring home milk!” Pregnant or not, many people would consider that grounds for divorce! So maybe Brown is trying to overcompensate for the lack of recognition of his accomplishments at home by exaggerating his “shaping the solar system” when discussing astronomy in public.

His other technique, the equivalent of politicians kissing babies, is the non-stop talk about his daughter, as if that somehow softens the image he cultivates as “the man who killed Pluto.” His blog entries, when not discussing nails in Pluto’s coffin, go on and on about his daughter saying, “daddy, daddy, daddy, look, look, look, I found a planet” when out observing the California sky. Personally, I can’t wait for the day in 2015 when she sees the photos of Pluto from New Horizons and says, “daddy, daddy, daddy, that Pluto sure looks like a planet to me!”

The point in all this is, Brown’s claim that the Pluto debate is “settled,” is far more about himself than it is about Pluto, Eris, or any Kuiper Belt Object.

And the statement that a non-binding, symbolic resolution is “dangerous to public understanding of science” is just plain ludicrous. If anything is harmful to public understanding of science, it is the notion that a self-appointed authoritative body such as the IAU can have four percent of its members adopt a nonsensical planet definition and then blindly expect the world to accept it because they, the “authorities,” have spoken.

In a Discover Magazine discussion of the Illinois proclamation, StevoR, a frequent commentator whose arguments make more sense than those of the IAU, listed twelve compelling reasons why Pluto is a planet, which, with his permission, I would like to quote here:

 1. The orbital clearing condition which was made up to eliminate Pluto is fatally flawed because it is itself too hard to define – what is meant by “cleared” & how far from the planet must the orbit be “cleared”? Strictly speaking this eliminates any object in our solar system as all planets have objects – comets and asteroids crossing their orbits, Jupiter has Trojan asteroids, Neptune has Pluto crossing its orbit, Earth has numerous near-earth asteroids such as Eros and so forth. A consistent application of this criterion would exclude all the planets of our solar system! (Even Mercury has sun-crossing comets and Icarus!)

2. A reductio ad absurdum approach reveals that this criterion fails because it leads to absurd results ruling out objects we’d clearly consider planets based on their location – a Jupiter or Earth-type planet hypothetically located in the Oort cloud would be excluded yet we’d clearly still call it a planet otherwise! Why then draw the line at smaller objects that would otherwise fit the planetary description ie. rounded by their own gravity and directly orbiting the Sun? (Or their common centre of gravity for “double planets.”)

3. In relation to forming planetary systems including historically our own, planetary orbits cross and interact in unpredictable ways. By the IAU’s “orbital clearance” criterion, these objects - even ones Jupiter sized and above – are NOT strictly planets because their orbits are not yet cleared – again failing the ‘reductio ad absurdum’ test. Eg : The earth before it was hit by the Mars-sized body that became our moon would NOT have been termed a “planet” because it had that Mars-sized object in its orbital path.

4. From point 3 above, we see that by IAU definitions planets cannot collide because their neighbourhood then isn’t clear – nor can they exist as binaries or “double planets” by the same logic. This appears contrary to common-sense and consistency. It also has potential for creating trouble with exoplanets given the so-far hypothetical but quite probable possibility that some extrasolar planets may exist in this form – even potentially twin Neptunes or Jupiters. Given that some would describe the Earth-Moon system as well as the Pluto-Charon one as such a ‘double planet,’ then a strict definition of the IAU rule may rule our Earth out of planetary status again clearly a ridiculous proposition!

5. Inconsistency and inapplicability in regard to exoplanets - the IAU definition excluded planets of other stars. Yet surely planets orbiting other suns are no less planets for not orbiting our star! Even more tellingly, at least one of the Pulsar planets, PSR B 1257+12 e is tiny – smaller than Pluto with only 1/5th our Moon’s mass raising a glaring inconsistency. Given PSR1257+12 e is counted as an exoplanet then Pluto, equally, should clearly count as a planet for the sake of consistency.

6. The “dwarf planet-dwarf” star analogy – just as dwarf stars are still stars so surely are dwarf planets still planets. Extrapolating the “dwarf planets don’t count” line to stellar astronomy would imply the Sun is not a proper star nor are 99 % of all stars – those 90% on the main-sequence and the 10 % of “stellar corpses” such as white dwarfs and neutron stars. Moreover, as with stars, the smaller the object’s size the greater its numbers! Therefore calling a planet “dwarf” should NOT rule it out of being considered a proper planet.

7. Problems with the “classical” planets term : the IAU defined “classical”; planets are restricted to our Earth’s solar system and it is hard to see how they apply to exoplanets or how the term can work usefully as a scientific description. Apart from differing immensely – Earth and Pluto are arguably far more similar worlds than Earth and Jupiter or Mercury or Neptune – they also clash with a previous understanding arguably much more apt of classical planets being those visible to the “classical” age peoples – the five original bright wanderers – Mercury, Venus, Mars, Jupiter, & Saturn. If that ‘classical’ term is retained, it seems best used in this sense as a historical and descriptive sense.

8. Sentimental, cultural and historical reasons – noting Pluto’s long-established and culturally scientific place as a recognised planet from its discovery in 1930 until its demotion in 2006. This also covers the slight to Clyde Tombaugh’s memory, widow and family plus the perceived political aspect of stripping from planetary status the sole planet discovered by an American. (BTW. I’m an Aussie with no connection to the US.)

9. The undemocratic manner in which the IAU ruling was made. For instance, of the 10,000 IAU members only 2,500 attended the Prague meeting that demoted Pluto and rejected the other planetary candidates, Eris, Charon and Ceres from planetary status. Furthermore, of those 2,500 only the merest handful – just 424 actually got to vote making therefore a very unrepresentative decision. Among those to excluded from voting and arguing their case in that last minute meeting were some highly relevant and articulate people - notably Pluto expert Alan S. Stern, head of the New Horizons mission. Stern’s summary of the IAU judgment was blunt : “ … idiotic. I have nothing but ridicule for this decision.” (Alan Stern, P.28, ‘Astronomy Now’, October, 2006.)

10. The decision to demote Pluto has had a generally negative reception from the general public and on public perceptions of astronomers - just ask the Illinoisans who must’ve had a fair number of people demand their action.
11. The first proposed IAU definition of ‘planet’ (that would have included Pluto, Eris and Ceres) was much better in terms of logical consistency and general application as well as being more easily explained, understand and applied - ie. two main criteria for planets are that they are objects circling a star directly which are not themselves stars or brown dwarfs and are rounded by their own gravity.

12. Pluto is a complex world with the key aspects of planets - it dominates its own satellite system of three moons (Charon, Hydra & Nix), has its own atmosphere, has a complex geology and weather system (of nitrogen frosting based on HST images and theory) and meets all the criteria for planethood with the sole exception of the problematic and, I believe, absurd “orbital clearance” criterion.”

As a personal note, I will add that I have the privilege of knowing the chief Illinois resident who lobbied for this resolution, Siobhan Elias of Streator, Illinois, the birthplace of Clyde Tombaugh.

Additionally, regarding the IAU ruling, most of the 2,500 attendees at the General Assembly who left before the vote fully believed that the resolution being voted on would be the one recommended by the IAU’s Planet Definition Committee, which advocated including Pluto, Charon, Ceres, and Eris as planets. They had no idea that a tiny group would violate the IAU’s own bylaws and push through a completely different resolution, the one that demoted Pluto, on the last day, with no vetting by the appropriate committee before placement on the floor for a vote. In other words, the astronomers who left early were deceived.

All this can be changed. One way you can make a difference is by joining the new Facebook cause, “Bring Pluto Back,” at . If you’re not a member of Facebook, joining is free, and there are a lot of pro-Pluto groups and causes to join and support. Organizers of this latest one encourage all to print out their protest letters and snail mail them back so they can be sent in bulk to the IAU.

The many issues involved in planet definition are presented in a thorough, objective analysis online at in a ten-part blog series by the Astroprof, a college professor of physics and astronomy, that began on February 2 and ended on March 10, 2009. Though there is a lot to read, I encourage anyone interested in this issue to take the time and read all ten entries.

Meanwhile, the real status of the Pluto debate? To be continued…

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