Planet Definition revised

See:-

http://www.space.com/scienceastronomy/060819_new_proposal.html


It is proposed that part of the planet definition should be a
requirement that :-

(a) is by far the largest object in its local population[1],
[1] The local population is the collection of objects that cross or
close approach the orbit of the body in consideration.


I can see that Pluto would by this lose its right to being a planet due

to Neptune.


But what of two similar sized objects the size of Earth in the same
orbit, maybe even orbiting each other as a binary system (whilst still
orbiting their star). surely these deserve to be planets


I still think the previous rules about the position of the COG make
more sense, and making the cut off size some arbitary size big enough
to keep the proposed number of planets to a reasonable number is
sensible.


I would simply say make this size bigger (or equal) than Pluto if we
still want Pluto.
Or
Bigger than (or equal to ) Mercury .


The idea of using a size big enough to make sphere by gravitational
forces might be elegant but is rather small , resulting in many more
planets than we can sensibly handle.

.

Relevant Pages

  • New Horizons Update - September 2005
    ... spaceship to Pluto. ... we were taught that our solar system ... contains four rocky planets on the inside, ... Neptune on a retrograde orbit that is the hallmark of gravitational ...
    (sci.space.news)
  • Re: "Pluto Now Called a Plutoid"
    ... orbit if there are no orbits intersecting it that are greater in mass than Ceres." ... If you include moons in consideration the first definition eliminates Earth, Jupiter, Saturn, Uranus, Neptune, Pluto, and Eris. ... In the second definition Pluto and Eris are sometimes planets and sometimes non-planets depending on how the other large Kuiper belt objects are arranged on any given day. ... The fundamental point here, which you're skipping over, is the IAU has never said what they mean. ...
    (rec.arts.sf.science)
  • Re: "Pluto Now Called a Plutoid"
    ... If you include moons in consideration the first definition eliminates Earth, Jupiter, Saturn, Uranus, Neptune, Pluto, and Eris. ... The second eliminates every candidate _except_ Eris, and even then Eris may sometimes temporarily lose planethood when other large Kuiper belt objects pass near it. ... In the second definition Pluto and Eris are sometimes planets and sometimes non-planets depending on how the other large Kuiper belt objects are arranged on any given day. ... Ceres itself is also sometimes a planet and sometimes not depending on where it is in its orbit relative to Mercury, Venus, Earth and Mars. ...
    (rec.arts.sf.science)
  • Re: Hey Mr. Hyde!
    ... Some other things to note about Pluto: ... It's moon, Charon, doesn't exactly orbit Pluto so much as BOTH ... Very near the Sun (in the vicinity of the ... inner 4 planets, for instance) it would likely be difficult for a ...
    (alt.lang.asm)
  • Re: Mercury Movies?
    ... several with Jupiter, a couple with Saturn, and even one ... anything more than just mention Mercury, Neptune, or Pluto (Pluto gets ... visit these planets? ... They deliberately skipped Mercury, and at the time of such a mission later in this century, Uranus and Neptune were way out of range. ...
    (sci.space.history)