Printable Version of Topic

Click here to view this topic in its original format

Unmanned Spaceflight.com _ Chit Chat _ The 'planet' Debate

Posted by: SFJCody Aug 27 2005, 07:04 AM

It seems that the IAU is having a tough time defining the term 'planet'. Why is a debate that is irrelevant to the understanding of the solar system proving so contentious?

Summaries of the suggestions so far and what they would do to the number of 'planets':

Mike Brown, discoverer of 2003 UB313:
Anything orbiting the Sun that is larger than Pluto is a planet.
+2003 UB313

Brian Marsden, director of the IAU's Minor Planet Centre:
Any newly discovered body orbiting the Sun must be larger than Mars to be called a planet.
-Pluto (but not Mercury)

Alan Stern, PI for New Horizons:
Any body orbiting the sun that forms itself into a spheroid through self-gravity is a planet.
+2003 UB313 and a dozen or more main belt asteroids and TNOs

Iwan P Williams, president of the IAU's planet definition working group:
No new planets, regardless of size.

Thoughts on this from the forum?
Also, does anyone have a complete list of the members of the planet definition working group? The IAU website is unhelpful.

Posted by: helvick Aug 27 2005, 07:39 AM

QUOTE (SFJCody @ Aug 27 2005, 08:04 AM)

Alan Stern, PI for New Horizons:
Any body orbiting the sun that forms itself into a spheroid through self-gravity is a planet.
+2003 UB313 and a dozen or more main belt asteroids and TNOs

I like this one - if you think about what we would call objects we find orbiting around other suns then I think that would be a reasonable way to apply broad categorisation.

Posted by: SFJCody Aug 27 2005, 11:07 AM

An article on the debate:

http://www.theglobeandmail.com/servlet/ArticleNews/TPStory/LAC/20050827/PLUTO27/TPScience/