2003 Ub 313: The Incredible Shrinking Planet?, No bigger than Pluto? Options

[Guest_BruceMoomaw_*]

(Thanks to Emily Lakdawalla):

http://sciencenow.sciencemag.org/cgi/content/full/2006/127/1

[Guest_JamesFox_*]

When I read that blog by Robert Roy Britt, I noticed the he acts as if it's a proven scientific fact that Pluto and 2003 UB313 are not planets, but the only reason he gives is that the 8 other planets have low inclination, as opposed to high ones. He also ignores (like most others), the fact that the term minor planet is already in use.

Many of those objecting to Pluto's status also seem to act as if the whole purpose of defining a planet is to provide a list for schoolchildren. In doing so, they tend to automatically ignore extrasolar planets - some even go so far as to declare that planets must orbit our sun (or even worse, insist that they must orbit at Neptune's distance or closer!) . They then compile lists of attributes that separate Xena and Pluto from the other 8, and use them to make anti-Kuiper belt planet definitions.

The inclination argument is one I've seen before. For example, I remember seeing a nice chart of inclination versus mass that seems to boost the anti-pluto case. However, a number of large extrasolar planets have very high eccentricities, even crossing the orbits of other planets in thier systems. Although their inclinations are unknown, it seems likely that some of them have high inclinations. In addition, would there be some sort of rule against having Pluto in a Quaoar-like orbit? Perhaps something like this exists in some extrasolar system.

I suspect that many people simply don't like Pluto or Xena, and feel that they are too small and wierd to be included alonside Mars or the Earth. So definitions are invented to exclude them, in an attempt to pretend that they are not being arbitary. Ignoring extrasolar planets makes this easier. When you look at these definitions more closely, however, hard boundaries and classifications are revealed as just as arbitrary as a lower size limit.

In the end, planets are largeish, round, and do not orbit planets seems to be the only general (if vague) definition in common use, before people started to try to kick Pluto out of the club. Since there is, in my opinion, no accepted scientific definition, a formal planet definiton should take the previous into account.

Also, we have to deal with the minor planet issue.