Planets again

[mmcirvin]

...And now the AP says the IAU has gone in the less expansive direction, distinguishing between dwarf planets and real planets and demoting Pluto. I can't tell exactly from the article but it sounds as if there's a qualifier that excludes objects obviously part of a population of similar bodies in similar orbits.

(The article claims that Pluto is disqualified because its orbit "overlaps" Neptune's, but that can't be right without further detail, or it would disqualify Neptune too! I would think that Pluto is disqualified because it's one of a whole population of similar bodies in similar orbits, some of which are of comparable or even greater size.)

Comments

[james-nicoll.livejournal.com]

The current definition of planet does not seem to be able to distinguish between stars, brown dwarfs and the objects we previously called planets.

[mmcirvin.livejournal.com]

I think they're more concerned about our solar system at the moment, where ambiguities mostly exist on the small end; but as they take into account all those extrasolar planet discoveries they're going to have to deal with the large end too.

[doctroid.livejournal.com]

Quoting the linked article, "a celestial body that is in orbit around the sun..." So stars and brown dwarfs are out (unless they're undiscovered sun-orbiters), as are, apparently, all those so-called extrasolar planets people have been discovering.