In 2017, Alan Stern et al. submitted a geophysical planet definition to the IAU for review which states

“A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters.”

Obviously, the IAU didn't accept it (as yet) but does anyone know what exactly the IAU stated about the draft and whether it is still being debated or entirely discarded etc.?

I'm just asking if it is possible to know the IAU's reaction. While users may have opinions on how reasonable the proposal is or isn't, please don't post opinions as answers.

  • $\begingroup$ What's the point of the question? $\endgroup$
    – James K
    Jan 3, 2021 at 19:59
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    $\begingroup$ They most likely were bored as there is little need and it just serves the purpose to get Pluto back to planethood. Evil tongues say that it's an endeavour to try and get back at least one planet discovered over in the new world. $\endgroup$ Jan 3, 2021 at 21:56
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    $\begingroup$ @JamesK to provide a mechanism by which an answer to "What was IAU's reaction to Alan Stern's 2017 proposal?" can be posted. Questions don't generally have "points", questions enable answers. $\endgroup$
    – uhoh
    Jan 3, 2021 at 22:01
  • $\begingroup$ @planetmaker Evil tongues claim it would just serve the purpose to get Pluto back to planethood. $\endgroup$
    – Greenhorn
    Jan 4, 2021 at 7:03
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    $\begingroup$ @Greenhorn yes... but what's the point? Pluto simply is not special. And there's no purpose served if we end up with dozens of planets. Dwarf planets is a useful category. $\endgroup$ Jan 4, 2021 at 9:19

1 Answer 1


In the linked article by A. Bouchard and another by J. Daley, the words "in the journal Lunar and Planetary Science" link not to a journal article but to a poster in a K-12 education session at the 2017 Lunar and Planetary Science Conference.

First author Kirby Runyon told Universe Today in 2017 that he would not submit this geophysical definition to the IAU process:

We in the planetary science field don’t need the IAU definition... If [the geophysical definition] is the definition that people use and what teachers teach, it will become the de facto definition, regardless of how the IAU votes in Prague.

It was not presented at the 2018 IAU General Assembly in Vienna. I don't know where Bouchard got "has been submitted to the IAU for review."


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