[meteorite-list] Astronomers to Decide What Makes a Planet

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Wed Aug 3 17:40:11 2005
Message-ID: <42F13995.D9CF6715_at_bhil.com>

Hi, All


    First, the definition of a planet.

    As for the lack of a formal definition of what is a planet, the IAU website says:
    "Definition of a Planet: The IAU notes the very rapid pace of discovery of bodies
within the Solar system over the last decade and so our understanding of the
Trans-Neptunian Region is therefore still evolving very rapidly. This is in serious
contrast to the situation when Pluto was discovered. As a consequence, The IAU has
established a Working Group to consider the definition of a minimum size for a Planet.
Until the report of this Working Group is received, all objects discovered at a distance
from the Sun greater than 40 AU will continue to be regarded as part of the
Trans-Neptunian population."

    You will note that it says, "the definition of a MINIMUM SIZE for a Planet,"
demonstrating that the understanding about size was NOT informal. Size was the issue for
the IAU. The Working Group was not scheduled to decide until NEXT summer.

    The 1999 denial by the IAU that it was considering demoting Pluto it a minor planet
can be found at:
<http://www.iau.org/IAU/FAQ/PlutoPR.html>
    It says: "Ways to classify planets by physical characteristics are also under
consideration," so they've been working on a definition for six years now. ONE WEEK?
Maybe they were already finished considering?
    It also says: "It is therefore the policy of the IAU that its recommendations should
rest on well-established scientific facts and be backed by a broad consensus in the
community concerned."
    Do you feel that the IAU can determine the "broad consensus in the community" about
the status of 2003UB313 in ONE WEEK?

    Of course, they may be responding quickly only because they AGREE with Brown and are
only waiting a week to see if anybody raises an objection they didn't think of. But my
guess is that the reason that Brown changed so dramatically to pushing the PLANET is that
he got the scuttlebutt that they were going to go negative. Scientists are gossips, like
all humans.


WHAT ARE THESE KBO's ANYWAY?
OR, MORE THAN YOU EVER WANTED
TO KNOW ABOUT THE OUTER SOLAR SYSTEM!

    As of May, 2004, there were 887 KBO's known. The number is certain to exceed 1000
soon.

    Some basic facts. The Kuiper Belt is believed to extend from Pluto out to 200 AU, or
nearly 20 billion miles out. Many KBO's, discovered early, have Minor Planet numbers and
are officially counted as asteroids.

    There are families of KBO's with similar orbits, like asteroids. (Another reason for
not calling them planets.)

    There are the Plutinos, with distances of about 39 AU, and this includes Pluto
itself. They are trapped in the 2:3 resonance with the mean motion of Neptune and often
cross the orbit of the planet near their perihelia, but never approaching the planet
itself. Pluto is the biggest Plutino and second is 2000DW (now ORCUS); it is at least as
large as QUOAOR and probably larger.

    There are the Classical Cubewanos, also named "CKBOs" (Classical Kuiper Belt Objects)
by Jewitt, occupies a region comprising between a = 40 to 47 AU. The Cubewanos do not
intersect the orbit of Neptune and have low eccentricities and inclinations. They are in
a very gravitationally-stable part of the Solar System. (50000) Quaoar is the largest TNO
presently found in the CKBO belt.

    There are a third group of TNO's (Trans-Neptunian Objects, another name for KBO's)
having high eccentricity with a semi-major axis located beyond 50 AU, has now been found.
This is the SDO (Scattered Disk Objects) with perihelia less than or close to 40 AU and
subject to the influence of Neptune. The origin of this group seems to have been through
the external migration of Neptune at the beginning of the Solar System. The orbits of
SDOs would have become very elliptical.

    However, a search for small TNOs carried out with the Hubble telescope found only 3
small TNOs of 25 to 45 km in diameter (mag 26 to 28), when 60 small TNOs were expected in
the studied zone. This lack of small TNOs has not yet been explained. If Hubble HAD
LOOKED IN THE RIGHT PLACE, it would have found 2003UB313 and 2003EL61 easily, as they are
13,000 times brighter than what was mentioned!

    One estimate dating from 2000 put forward the possible existence of 800 million [KBO]
objects greater than 5 km in diameter. The estimates for the total mass of KBO's is very
small -- 1/10th of an Earth mass for the entire Belt. The discovery of larger and larger
KBO's is eating up that mass estimate like a pig. There will almost certainly be more
mass than that there. One study of the Pioneer anomaly says it proves that there is more
mass than that in the Kuiper Belt, and the study was ignored. Maybe it shouldn't be
ignored.

    The existence of "families," the eccentric orbits, the numerous small objects, the
existence of small binary KBO's, all remind astronomers of the asteroids, of course, and
they have tended to regard the Plutonians as such. But there would be asteroid-like
Plutonian Minor Planets and planet-like Plutonian Major Planets, both, if they are a
compositional class, like the Terrestrial Planets, major and minor.

    Until these newest discoveries, there was an argument about whether or not there was
an a disk of objects beyond 50 AU.
    Until now, the argument was: "The apparent absence of TNOs having near-circular
orbits beyond 47 AU could be a sign that a massive body is situated beyond 50 AU. With a
quite low eccentricity, it may be in a very inclined orbit, and therefore has not been
found to date. This massive body some 2000 to 4000 km in diameter could be orbiting on
average some 62 AU from the Sun, with q = 49 AU, Q = 78 AU and e = 0.21. Its visual
magnitude would be between +18.5 and +21.5 for the case having an albedo of 0.04, or
+16.2 to +19.7 if having a high albedo of 0.3."
    2003UB313 is at least 3300 kilometers and may be 4500 or more. With a Pluto-like
spectrum, it would be 4 to 8 times more massive than Pluto itself. The predictor was
right about high inclination orbits.

    A study in 2001 by Brett Gladman et al. looked to prove the existence of an Extended
Scattered Disk, which could contain at least 10,000 "SDOs" greater than 100 km, and even
more than in the SKBO zone, with high "a" and "q" > 40 AU. (48639) 1995 TL8, 2000 CR105,
as well as a number of unrecovered KBOs should be members of this Extended Scattered
Disk.
    There are 12 "asteroids" with orbits beyond 100 AU, out to 1000 AU. Difficult
objects, some are comets. But which ones? Six are between 100 and 121 AU. Three are
between 216 and 227 AU. A pair is at 509 and 518 AU.


    "The massive object named 2003 VB12 (SEDNA) discovered in November 2003 could also be
a member of this extended diffuse disk." SEDNA is unusual in that it is so red and so
dark. It was initially assumed that the redness and the darkness were linked, and that
the redness was organics, like the ones that were supposed to cover Titan (but don't seem
to). Some think it's from the Oort Cloud. One thinks it may be extra-solar, from somebody
else's Oort Cloud!
    But spectra failed to show organics.
    I suggest that if the Jovian-type planets' satellites are captured Plutonian planets,
then the redness of SEDNA could be due to sulfur, if IO is a captured Plutonian
planet(oid). If there are others, they could be very dark bodies indeed, like Sedna,
almost the darkest object in the solar system.
    Somebody check those SEDNA spectra for the allotropes and metamorphs of sulfur and
its compounds.

    The director of the Lowell Observatory, Dr. Robert Millis, says about KBO's, before
all these new discoveries:
    "A comprehensive survey of the Kuiper Belt to the extent that that is possible needs
to be done - that is not what we're doing now - we're doing a reconnaissance - so I think
that over the next one to two decades, astronomers will be very actively engaged in
exploring what is a newly discovered major structure in the Solar System."

    That's A NEWLY DISCOVERED MAJOR STRUCTURE IN THE SOLAR SYSTEM, the Plutonian planets.



Sterling Webb
--------------------------





Ron Baalke wrote:

> >
> > Hi, Ron,
> >
> > You'll notice that I put quotes around the word "rules."
>
> You also referred to it as a game, which is not. Any classification scheme can
> be revised - and in fact, should be allowed to be revised when new data
> presents itself.
>
> > Yes, there is no formal definition for a planet. There never has been, only a
> > working understanding of what was meant.
> > There were differences; it has been a topic of discussion. But, there are
> > "working rules," by which I mean that one knows what others in the field think and
> > why.
>
> The 'working rules' varied depending on who you talked to. Thus the need for a
> formal definition.
>
> > Next week's IAU decision is only a momentary thing, always subject to revision.
>
> The IAU decision will be first formal definition of a planet. As I mentioned before,
> any classification scheme can and should be revised as needed.
>
> Ron Baalke
> ______________________________________________
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Received on Wed 03 Aug 2005 05:39:33 PM PDT