Saturday, June 19, 2010

The International Astronomical Union

It has been rather quiet on the "Pluto/planet" debate and the role and significance of the The International Astronomical Union [IAU]. As readers may know that there is one Ms. Laurel Kornfeld who is an ardent supporter of Pluto's status as a planet and has offered detailed reasoning for such support here and in our email correspondence. [Use the blog's search engine for many items on Pluto.] Many times the IAU has been the focal point of discussion. Neither Laurel nor I can agree on the merits of decisions rendered by the IAU members that realized a final decision regarding Pluto's status.

It is my opinion that the IAU is making the correct decision for the time being and that such a decision would be subject to modification. The IAU has been around for a long time making hundreds of decisions without vehement contest and as far as I am concerned the IAU is a well-established body of astronomy experts making decisions for astronomers using sound scientific criteria. But the line was crossed when Pluto was demoted based on new criteria...a true class between scientists and the populace. If the IAU is not to be trusted in their decisions, then what body of experts would?

The International Astronomical Union — the first 90 years

"Pluto and the Developing Landscape of Our Solar System"

The discovery of Pluto

Nearly eighty years ago an astronomer working at the Lowell Observatory in the United States made a discovery that would ultimately initiate a dramatic change in the way we look at our Solar System. The young astronomer was Clyde Tombaugh, an observing assistant working at the observatory made famous by the great astronomer Percival Lowell. Tombaugh was continuing the search for an elusive planet – planet X – that Lowell had believed (incorrectly) to be responsible for perturbing the orbits of Uranus and Neptune.

Within a year, after spending numerous nights at the telescope exposing photographic plates and months tediously scanning them for signs of a planet, Tombaugh saw what he was looking for. At around 4pm on the afternoon of 18 February 1930 Tombaugh began comparing two plates taken in January that year showing a region in the constellation of Gemini. As he flicked from one plate to the other, trying to see if something moved slightly between the two (the tell-tale sign of the planet he was hunting), he spotted something. In one part of the frame a small object flitted a few millimetres as he switched between the two plates. Tombaugh had found his new planet! (Stern & Mitton, 2005)

The changing landscape of the Solar System

The object Tombaugh had discovered was named Pluto, a name officially adopted by the American Astronomical Society, the Royal Astronomical Society in the UK and the IAU. It is a frigid world, billions of kilometres from Earth, and 30 times less massive than the then-smallest known planet, Mercury. But Pluto was not alone. It was found to have three satellites. The largest, Charon, was discovered in 1978. The smaller two were discovered using the Hubble Space Telescope in 2005 and officially named Nix and Hydra by the IAU in early 2006 (read more) .

The view of our solar system's landscape began to change on August 30, 1992 with the discovery by David Jewitt and Jane Luu from the University of Hawaii of the first of more than 1000 now known objects orbiting beyond Neptune in what is often referred to as the transneptunian region. More generally these bodies are often simply labelled as Trans-Neptunian Objects (TNOs).

With so many Trans-Neptunian Objects being found, it seemed inevitable that one or more might be found to rival Pluto in size. On the night of the 21 October 2003, Mike Brown from Caltech, Chad Trujillo from the Gemini Observatory and David Rabinowitz from Yale University were using a telescope and camera at the Palomar Observatory in the US to search the edge of the Solar System. That night they imaged a region of sky showing an object moving relative to the background stars. Later analysis showed that they had discovered another cold world, around 2500 km across, orbiting the Sun. Subsequent observations showed that the new object, initially named 2003 UB313 according to the International Astronomical Union's protocol on the initial designation of such objects, was more massive than Pluto and that it too had a satellite (read more) . With an object larger and more massive than Pluto now beyond Neptune and ever more of these Trans-Neptunian Objects being discovered, astronomers were beginning to ask: "Just what constitutes a planet?"

A new class of objects and how to define a planet

The IAU has been responsible for the naming and nomenclature of planetary bodies and their satellites since the early 1900s. As Professor Ron Ekers, past president of the IAU, explains:

Such decisions and recommendations are not enforceable by any national or international law; rather they establish conventions that are meant to help our understanding of astronomical objects and processes. Hence, IAU recommendations should rest on well-established scientific facts and have a broad consensus in the community concerned. (read the full article) .

The IAU decided to create a committee to gather opinions from a broad range of scientific interests, with input from professional astronomers, planetary scientists, historians, science publishers, writers and educators. Thus the Planet Definition Committee of the IAU Executive Committee was formed and quickly went about preparing a draft resolution to put to the members of the IAU. After the final meeting in Paris the draft resolution was completed. One crucial aspect of the resolution is described by Professor Owen Gingerich, Chair of the IAU Planet Definition Committee: "On the scientific side, we wanted to avoid arbitrary cut-offs simply based on distances, periods, magnitudes, or neighbouring objects". (read more) .

The final resolution

The first draft proposal for the definition of a planet was debated vigorously by astronomers at the 2006 IAU General Assembly in Prague and a new version slowly took shape. This new version was more acceptable to the majority and was put to the members of the IAU for a vote at the Closing Ceremony on the 24 August 2006. By the end of the Prague General Assembly, its members voted that the resolution B5 on the definition of a planet in the Solar System would be as follows:

A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(read more)

Dwarf Planets, plutoids and the Solar System today

The IAU Resolution means that the Solar System officially consists of eight planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. A new distinct class of objects called dwarf planets was also decided on. It was agreed that planets and dwarf planets are two distinct classes of objects. The first members of the dwarf planet category are Ceres, Pluto and Eris, formerly known as 2003 UB313. Eris was named after the IAU General Assembly in 2006 (read more) . Eris is the Greek god of discord and strife, a name which the discoverer Mike Brown found fitting in the light of the academic commotion that followed its discovery.

The dwarf planet Pluto is recognised as an important prototype of a new class of Trans-Neptunian Objects. The IAU has put given a new denomination for these objects: plutoids.

Today the resolution remains in place and is a testament to the fluid nature of science and how our view of the Universe continues to evolve with changes made by observations, measurements and theory.


Stern, A., & Mitton, J., 2005, Pluto and Charon: Ice Worlds on the Ragged Edge of the Solar System, Wiley-VCH 1997

History of the IAU. Birth and First Half-Century of the International Astronomical Union


Adriaan Blaauw

ISBN 0-7923-2980-5

This book describes the birth and early development of the International Astronomical Union, the world-wide union of professional astronomers that over the past 75 years played an important role in the development of astronomy. However, much attention is also paid to the Union's successful bridging political controversies and maintaining the ties between astronomers in times of war or heavy political tension. The book therefore is of interest not only to astronomers - professional as well as amateur - but also to students of the history of modern science in general. The author has witnessed the development of the Union over the past 55 years, the years 1976 - 1979 as its President.

International Astronomical Union

International Astronomical Union [Wikipedia]


Laurel Kornfeld said...

Hello and thanks for the mention. I almost didn't see it, as I'm performing in a Renaissance faire this weekend.

Things aren't really quiet on the Pluto debate. Dr. Stern just wrote his latest New Horizons update, in which he makes sure to refer to Pluto as a planet. New Horizons is now halfway between Earth and Pluto. The Inwood Astronomy Club in New York held a well-attended event called "The Problem with Pluto" and determined that the "problem" is us, specifically, human issues regarding classification and wanting things to fit into neat categories. In March, Dr. Neil de Grasse Tyson's Nova episode aired, and Tyson made it clear there that this is an ongoing debate. Alan Boyle has written a great book, "The Case for Pluto," and I hope to finish my book, "The Little Planet that Would Not Die: Pluto's Story" this year.

The flawed process used by the IAU in 2006, the fact that they violated their own bylaws to pass this resolution, that they excluded 96 percent of their membership in the vote, and their continuing refusal to respond to astronomers asking for a reopening of the debate all constitute unprofessional behavior and illustrate why the IAU lost a lot of its credibility in adopting this resolution. It most certainly is not a "final" decision. A lot of planetary scientists believe the appropriate time for such a decision is when we get the data from New Horizons. Five more years.

Mercury said...

Renaissance faire? That's a little early isn't it? Such activities won't start here until late September and into early October. :)

Do you have a suggestion for the IAU...modify it or replace it? They do have a rich history of doing things correct. And this aberration over Pluto is nothing more than a burp.

Laurel Kornfeld said...

I didn't know there is a specific season for Renaissance Faires, but given the fact that we were out all day yesterday in extreme heat and humidity, with several people passing out from heat exhaustion and a child stung by a bee, it sounds like September or October would be a better time for it! We're on next weekend again, and I'm hoping for low humidity and a lot less heat.

The IAU did a lot of damage to its credibility and rich history with the fiasco of 2006. They further compound the effort by their continuing refusal to reopen the discussion. If the 2006 decision is an aberration, they should admit it and go back and redo the entire thing.

Here, specifically, is my suggestion for the IAU, made in an open letter to the 2009 General Assembly last year. The entire text is available on the August 6, 2009 entry of my Pluto Blog.

"I am writing to urge this General Assembly to officially reopen the planet definition issue, in light of the tumultuous, controversial, and abrupt manner in which it was addressed at the 26th General Assembly in 2006. Specifically, I ask that you reconsider and add Resolution 5b from 2006, which would establish “planets” as a broad, umbrella category under which both classical and dwarf planets would be included.

Doing this amounts to reconsidering a simple amendment that, if adopted, would supersede the 2006 vote on this resolution and thereby establish dwarf planets as a subcategory of planets.

Additionally, I urge you to place a resolution on the table to allow electronic voting on all resolutions by all members of the IAU, for the purpose of including the voices of astronomers who for various reasons, including financial difficulties and family responsibilities, are unable to attend the two-week General Assemblies in person. This will make IAU processes more inclusive of its membership and bring them in line with the digital reality of the 21st century."

Mercury said...

That all may fall of deaf ears.

Take this pill and you will feel better after reciting the following :)...

"Pluto is not a planet."

"Pluto is not a planet."

"Pluto is not a planet."

"Pluto is not a planet."

"Pluto is not a planet."

Remembering the fashion of the day, Fall would be better suited for a Renaissance Festival.

Laurel Kornfeld said...

You asked for my suggestion to the IAU. Since many others, including professional astronomers, are saying the same thing I am, if it does "fall on deaf ears," that shows that the IAU is not the upstanding organization some people believe it to be.

Sorry, but I'm allergic to that pill, and even though I am an actress, there are some lines I just won't say. The line you repeat five times is one of those. I would rather wear full Renaissance garb on the hottest day of the year than ever say something so contrary to my convictions. :)

Mercury said...

"...the IAU is not the upstanding organization some people believe it to be."

Isn't that a bit strong for an organization that "does" represent commonality on astronomical decisions of classification as well as other astronomical features. To condemn a 90 year old institution for a single dispute is somewhat misplaced. Perhaps error[s] were made and in time a satisfactory mutual agreement can be made but I maintain that displacing Pluto from the "Big Nine" is not that an egregious event; that Pluto can maintain popular status and astronomical classification status [by the IAU].

Nevertheless, did you know that the Frisbee was originally called the "Pluto Platter"?

Take only 1/2 of the special pill and recite five times "Pluto might not be a planet." :)

Laurel Kornfeld said...

Even half of "that special pill" induces a horrible allergic reaction. Sorry, no can do.

The IAU's bungling of this is not a "single dispute." They have repeatedly been asked by professional astronomers who oppose the demotion to reopen the discussion, and they have continually refused to do so. They passed on an opportunity to revisit the issue at the 2009 General Assembly, continuing the alienation of astronomers who don't support their position. Many errors were made in both the process used to reach the 2006 decision and in the decision itself. I would like to see the IAU follow the example of President Obama, who admits when he messes up and then does what he can to correct the situation.

Yes, I do know about the Frisbee once having been called the "Pluto Platter."

There is no "may be" about it. Pluto is a planet. :)

Mercury said...

Take only 1/4 of the special pill and recite five times "Pluto might prove by definition to not be a planet." Work with me on this. :)

I agree that errors and severe politics to happen on a regular basis in just about everything including an IAU vote. And it would be wise to negate such decisions and admit culpability. But certainly a new definition must satisfy members of the IAU and general public.