[X] My Assistant

[JRehling]

Probably some perfect "grand tour" type alignment, where each spacecraft-planet encounter is as close-in to the planet as possible for a departure trajectory that's approximately tangent to the planet's orbit or as close to tangent as possible.

Eris is also well off of the ecliptic at present (and for a long time coming). I doubt that keeping things in the ecliptic for three flybys then counting on Neptune to provide all of the work to acquire a high inclination is feasible. Maybe a Jupiter-Saturn combo could do it, assuming the rings weren't a problem.

That would actually be a scenario that would unfold fairly often.

Uranus is actually in a pretty good position right now for an assist to Eris, but it'll soon move out of that good position and not come back for 8 decades. Neptune, however, is moving into position, but again, Neptune can't bend the path down in very good proportion to Jupiter's bending it out.

In only 230 years or so, Eris will come within 40 AU of the Sun. Let's plan on an Eris Orbiter/Lander then. Start the buzz now.

[Alan Stern]

You probably already know about The Great Planet Debate meeting coming this week near DC, if not, see:
gpd.jhuapl.edu.

To register for Great Planet Debate conference web participation, click: http://tinyurl.com/6xcqec
Watch the talks and debate on line!

-Alan

[surreyguy]

Maybe I'm just belabouring the obvious here, but while some categorisations (e.g., all bodies whose name begins with 'E') are arbitrary, the good categorisatons are those which reflect theory in some way. That's what distinguishes categories such as '>2000km diameter' from 'roundness'. The thing which I guess I find odd is when people find it hard to switch viewpoint, and thus what categorisation is relevant for the discussion at hand. If you want to discuss tectonic features then the roundness criterion is relevant; if you are talking about the way the architecture of the Solar System has been sculpted over time, then orbital dominance is what you want.

Of course, some definitions may be more useful than others for the purpose of knowing which committee gets to name a body, but you'd think that issue could be settled without people crying 'but what about the children'...

I guess I'm saying that I don't think that there's any such thing as an inherent quality of 'planetness' which we can know - that seems a no brainer, put like that, but a lot of the arguments one sees seem to be predicated on something like it. For example, the use of 'what if we discovered...' scenarios.

[mcaplinger]

...while some categorisations are arbitrary, the good categorisatons are those which reflect theory in some way.

I'm not sure I would use "arbitrary" and "good" as opposites like this. Many (most?) uses of terminology are "arbitrary" but have managed to avoid the emotionalism and controversy that this one has caused.

If it were up to me, I would have just said that everything Pluto-sized and bigger was a planet and everything smaller wasn't, but somehow this has been dismissed as being too "unscientific".

The whole thing reminds me of the vociferous debate I was involved in about whether longitudes should be positive to the east or west (also horribly confused by the IAU.)