"Margo Schulter" wrote in message
...
George Dishman wrote:

According to this, no:

http://www.iau2006.org/mirror/www.ia...602/index.html

A planet must be "in orbit around the Sun". Even
if the dwarf were part of a binary with another
main sequence star, it would be a planet, just
as "extra-solar planets" are no longer planets!


Hello, there, and while I'm not sure about the first part of
your statement (may we could clarify this binary star
situation you raise), ..

At some point there needs to be a dividing line drawn
between a binary system and a star with a planetary
system. Based on your other posts, I would say the
latter is easy, it is one in which only one object
reaches the point of fusion. If more than one achieves
that then it is a binary star system, possibly also
including planets and other debris.

If none reaches fusion it could be harder for the
case of systems where no one body dominates. You
get free-floating double planetary systems I suppose.

I think that I can clarify the
second point concerning "extra-solar planets."

Actually IAU Resolution 5A restricts its domain to
classifying objects in our own solar system; the question
of defining planets elsewhere is simply left unaddressed,
and likely reserved for a future meeting (the next one in
Rio, 2009).

Well that may be the idea but the outcome has been
to produce a definition of the word "planet" that
should find its way into most good dictionaries.
The idea that an object identical to Earth but
around another star identical to the Sun might not
be a planet (but we haven't decided yet) is not
one that is going to be treated with any respect.

The actual text says this:

"Contemporary observations are changing our
understanding of planetary systems, and it
is important that our nomenclature for
objects reflect our current understanding.
This applies, in particular, to the
designation 'planets'. The word "planet"
originally described "wanderers" that were
known only as moving lights in the sky.
Recent discoveries lead us to create a new
definition, which we can make using currently
available scientific information."

Note in particular "Recent discoveries lead us to
create a new definition" for the "designation
'planets'." That is not restricted to the solar
system but states it is a definition of the word.
It goes on
"The IAU therefore resolves that planets and
other bodies in our Solar System, except
satellites, be defined into three distinct
categories in the following way:"

so there are only three categories of planets and
all reside in our solar system.

There is a note saying

"An IAU process will be established to assign
borderline objects into either dwarf planet
and other categories."

but I see nothing whatsoever on the page to say
that this definition is not applicable to objects
outside the solar ystem or that it will be further
considered in 2009.

Thus the resolution doesn't directly affect the status of
any extra-solar planet, much less remove its planethood,
which is simply left officially unaddressed.

Sorry, that isn't the case according to the page
I cited. That's why I asked if this was merely
one of the drafts and the final resolution
corrected these problems. Replacing "the Sun" by
"a star" would have resolved that problem (with
perhaps a footnote regarding binary systems etc.).

We can debate whether the IAU was wise to adopt a planetary
taxonomy for objects in our own solar system only, as well as
the wisdom of its specific conclusions. However, I would
emphasize that extra-solar planets are just as much planets
as they were on August 23, the day before the resolution was
adopted.

While your interpretation may seem resonable, it
is not the resolution that was passed.

Hmmm, is that really the version that was adopted?

In my post in this thread I include a proposal giving the
text of the adopted version plus some suggested changes ..

Tough luck, the meetings have finished and the
resolutions passed. I'm sure a lot of other people
have alternative views too, but then the whole
point of the process is to reach a consensus that
is at some level acceptable to the majority and
after that we are all stuck with it. I don't intend
to stop considering extra-solar planets to be planets
but that appears to be the official result.

George