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Meade 4M | September 1, 2006 |
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| Jocelyn Bell Burnell, the discovery of pulsars, with her umbrella over the balloon for classical planets and cereal + Pluto for dwarf planets. The umbrella was voted down when the resolution 5b to add the term "classical" was defeated. (Jay M. Pasachoff/Science Faction) |
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The membership of the IAU today was in a forward-looking mode, and defined a category called "dwarf planet" to include Pluto and the many similar objects still to be discovered. They did not let sentiment keep them from removing Pluto from the category of planet that it had held for 75 years.After changing versions of resolutions circulated and were modified for several days, a "final" resolution was distributed today, only to be modified at lunchtime and again modified from the floor. The main change of the day was to put "dwarf planet" in quotes to make clear that we were defining the pair of words together. Both planets and dwarf planets orbit the Sun and have enough gravity to make them round or nearly so. The distinction between the categories is that dwarf planets have not "cleared the neighbourhood" around their orbits. Ceres, the first asteroid to be discovered, is a dwarf planet under the new definition. Satellites are excluded, at least for the time being, so Pluto's moon Charon is not a dwarf planet. My only official comment to the meeting today, though I had spoken to a number of people behind the scenes to try to represent Pluto's case for planethood, was to correct a potential miswording in the revised main resolution by clearly excluding satellites in the resolution's preamble. |
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| Resolution-committee chair Chris Corbally with Mark Sykes of the Planetary Science Institute at the podium speaking against the main resolution for defining "planet." (Jay M. Pasachoff/Science Faction) |
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An attempt to make the category of "dwarf planet" parallel to that of "classical planet" failed, with a clear majority holding up yellow voting cards against the proposal to add the word "classical." It was made clear that dwarf planets are not planets; the answer to the question "Is Pluto a planet" is "no." One could say, "No, but it is a dwarf planet."The meeting then went on to resolve that "Pluto is a 'dwarf planet'by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects." The vote was 237 in favor and 157 against, with 30 abstaining, though there seemed to be many more than 424 people in the Congress Hall. The following vote, on a resolution that "this category is to be called 'plutonian objects'" failed by the narrowest of margins: 183 against versus 186 for, in a vote conducted by IAU President Ron Ekers of Australia. |
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| With IAU President Ron Ekers at left, Jocelyn Bell Burnell describes the main resolution. (Jay M. Pasachoff/Science Faction) |
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Though there was a realization that the count of votes was not completely accurate, there was overwhelming sentiment against having a revote. The decision on a name for the category is now left for the International Astronomical Union's executive committee, to be headed for the next three years by Catherine Cesarsky of the European Southern Observatory. She, her husband (Diego Cesarsky), and I were Harvard graduate students and Caltech postdocs together.Richard Binzel of MIT, who spoke for the Planet Definition Committee, said that "clearly, more Plutos certainly remain to be discovered." The discussion was conducted by Jocelyn Bell Burnell, in 1968 the discoverer of pulsars.She said,in answer to Jean-Claude Pecker's question as to what would be the status of a Neptune-mass planet that might be eventually discovered way beyond Pluto, "We'll solve it when we get to it." Dr. Bell had brought a Pluto stuffed animal and a box of cereal to represent Ceres, and at one point arranged them on the stage under an umbrella she had brought to represent one of the possibilities being voted upon. She wound up separating them. Her stage table also boasted of a balloon to represent the 8 regular planets and a small lemon-sized object to represent the third category of solar-system objects that aren't satellites: to be known as "small Solar System bodies." They include asteroids, comets, and other types of objects. |
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| The beginning of the final debate, with resolution-committee chair Chris Corbally at left, IAU President Ron Ekers at the table, and Jocelyn Bell Burnell standing at right. (Jay M. Pasachoff/Science Faction) |
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There was no specific mention of the particular object in the outer solar system, 2003 UB313, that because of its size now thought to be slightly larger than that of Pluto led to the controversy. Its naming will be handled through some IAU process, as will the naming of other, similar objects. Mike Brown of Caltech has a dozen candidates in this category. |
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| A Prague statue of Tycho and Kepler. (Jay M. Pasachoff/Science Faction) |
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The results of today's votes will all take some time to sink in, and we expect comments from newspapers and schoolchildren all around the world. In the meantime, the research of our Williams College and MIT group of faculty and students on the size of Pluto and Charon and the atmosphere of the former continues, and NASA's New Horizons spacecraft continues on its path to reach the Pluto-Charon system, whatever it is, in 2016. |
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| Prague's astronomical clock from 1410, though it was extensively redone in the 19th and 20th centuries. (Jay M. Pasachoff/Science Faction) |
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Williamstown, August 30The IAU's decision has met with kudos from some places and negative reactions from others.A petition signed by hundreds of astronomers opposing the decision and promising not to adopt it has circulated. Since it is signed by the head of the New Horizons mission and other very knowledgeable planetary astronomers, it has to be taken very seriously. I have updated the section in my Peterson Field Guide to the Stars and Planets to indicate what went on, but I am ending with a statement that it remains to be seen how widely adopted the new definition will be. Fortunately, I have a new printing of my field guide about to go to press, so the new material, along with general updates through 2017, will soon be widely available (www.williams.edu/astronomy/fieldguide). |
| Classifications: Beginning Observing, Advance Observing, Astronomy Outreach, Meade News, General, Recent Discoveries| 9/1/2006 - 0/0/0 |
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