On 13 Jun 2006 08:34:36 -0700, "Double-A" wrote:


steve wrote:
With this set to be finalised fairly soon in September 2006 I think it
is essential that a few sensible parameters are added.

1) A body in orbit around a star.

2) Size must be larger than Pluto ( or another agreed specified size
and mass) to give a minimum size UNLESS extra-terrestial life is found
on the planet when a much smaller size would be allowed.

3) If the size of a moon is similar (to a stated percentage e.g. 80%)
to the larger body in its group it to can be called a planet if it
meets (1) and (2)
Thus it is possibe to have binary planets.

4) It would probably be necessary to specify a maximum distance from
the star in which the planet is in orbit to dis-allow wandering rocks.


Should there be a maximum size for a planet?

What about brown dwarfs in orbit around a star?

Brown dwarfs give light, but they do not have fusion reactions
occurring as is necessary in the usual definition of a star.

What about the continuum of objects between the size of Jupiter and
brown dwarfs?

Where do we draw the line?

And on the low end, why shouldn't Ceres be the minimum planet size?

It has almost half the diameter of Pluto.

It is spherical.

It contains 25% of all the mass in the asteroid belt.

It fills a gap in the planet spacing predicted by Bode's Law.

It probably has more water (ice) than all the fresh water on Earth.

And it orbits the Sun and has a 9 hour day.


http://www.astrobio.net/news/modules...cle&sid= 1711

Ceres for 5th planet!

Dobule-A


do away with "planet" as some kind of superior designation. all
current "planets" keep their common designation. everything else gets
a catalog number and keeps it.

planets are a romantic designation. the stuff we are discovering now,
in volume and number, exceeds any ability to stay romantic about it.

maybe, someday, when people are living on these bodies they can come
up with their own vernacular ID name. meanwhile, its pointless trying
to categorize objects that may have designations that reside in
several classes. its all about the gray, not black and white.