Friday, August 25, 2006
Planets As Neighborhood Bullies.
The best complaint so far focuses on the reguirement that a planet have cleared its orbital neighborhood of other objects. Some astronomers in the story linked below point out that more than one Kuiper Belt Object crosses Neptune's orbit, Pluto and Charon, for example. If being a neighborhood bully is a requirement for planethood Neptune is barely working at it. Astronomer Harold Weaver has a more fundamental objection that makes a lot of sense.
"'Regarding the resolution itself, I'm with Andy Cheng in concluding that the situation is still somewhat muddled. What exactly is meant by a planet 'clearing its neighborhood?' Since many 'plutinos' ... (including Pluto) ... cross Neptune's orbit, I'd say Neptune's neighborhood still needs some clearing!
'It just seems a bit risky to me to base a definition on a theoretical construct ('dynamically cleared regions') that's only approximate at best and may change significantly as our understanding of planet formation evolves over time.
'I further note that there have been particularly large swings in the theories of outer solar system dynamical evolution during the past decade. What was 'conventional wisdom' five years ago has been replaced with the latest fad, and I don't expect that situation to change any time soon.'" (Here.)