In The Field

After the IAU: it’s not over yet

Oh dear, look what’s circulating on the web. Here we have a petition against the new definition of a planet, seeking scientists’ support for a boycott of the IAU resolution. I will provide some context in my next post, here.

Sent: Fri 8/25/2006

Subject: Petition Protesting the IAU Planet Definition

Dear Colleagues –

Less than 5% of the astronomical community voted at the Prague IAU for a definition of ‘planet’ that uses dynamics (location) rather than intrinsic properties to decide if an object is or is not a planet. This result is counter to other classification schemes in astronomy (e.g., stars, galaxies, nebulae, even asteroids) in which dynamical context does not play a controlling role.

Furthermore, it produces results that are incongruous and cannot be extended within our own solar system or to extra-solar planetary systems without producing immediate results that are patently absurd: e.g., a Neptune-sized object discovered beyond 150 AU could not be a planet, the presence of an Earth orbiting its star between a Jupiter and a Saturn would mean the Earth could not be considered a planet since it could not clear its “neighborhood”.

This definition also excludes Pluto from planethood in our solar system, something that is both scientifically questionable and publicly problematic. Both Pluto and a distant Neptune would be classified as a “dwarf planet”, which is not to be considered a subcategory of “planet”.

If you agree that this process and its consequences are flawed, you are invited to sign a web-petition protesting this action at

The petition will be transmitted to the IAU.

Please redistribute this message to planetary and astronomical colleagues only. It is not meant to be a public petition. Thank you.

Mark Sykes (Planetary Science Institute)

S. Alan Stern (Southwest Research Institute)

Faith Vilas (MMT Observatory)

Christopher T. Russell (University of California, Los Angeles)

Larry Lebofsky (University of Arizona)

Ted Bowell (Lowell Observatory)

Carolyn Shoemaker (US Geological Survey)

David Levy (Jarnac Observatory)

David Grinspoon (Denver Museum of Nature & Science)

Harold Weaver (Applied Physics Laboratory)

David Weintraub (Vanderbilt University)

Amy Lovell (Agnes Scott College)

*Weblink removed to respect the organisers’ wish that the petition represent the views of the scientific community.


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