[X] My Assistant

[David]

That would be about like calling Europe a continent.

I don't actually hear this much any more, though maybe it's in some textbooks. Mostly I hear Eurasia, Africa, North America, South America, Antarctica. And (maybe) Australia.
Australia is actually a good comparison to Pluto: too small to be a good continent, too big to be an ordinary island. That battle still (quietly) rages on. Pluto may remain stuck in limbo for centuries to come.
I take the practical approach: count 2003 UB313 and Pluto as planets, and any other sun-orbiters as big or bigger than Pluto, until the number of the latter gets too big to deal with, if it ever does. I hear talk of a thousand KBOs bigger than Pluto, but from where I'm sitting that just seems fanciful. Find 'em and then we can talk. If and when we get half a dozen or more Pluto-plus KBOs, then we can put them in a new category -- just as we did with the main belt asteroids. That business sorted itself out over half a century -- why try to force things to go faster? And if it turns out that there are no other KBOs bigger than Pluto, or only two or three, then we'll still have a decent number of planets (anything under thirteen is certainly manageable) and we won't be embarrassed by having jumped the gun on a bogus prediction.

[SFJCody]

I'm going to agree with Bruce; of all the proposals I've heard so far, I like this one the least. Why is an icy body discovered in 1930 'historical' while an icy body discovered in 2005 is not? Did history stop last year? How can this possibly be applied to extra-solar planets?

[Guest_BruceMoomaw_*]

Moreover, the analogy to Europe doesn't hold. Just about everybody on Earth (I hope) knows that Europe is really just Asia's biggest peninsula -- but if the IAU goes with this harebrained scheme, most people are going to think that Pluto is the biggest KBO. Pfui.

[SFJCody]

http://aa.usno.navy.mil/hilton/AsteroidHis...norplanets.html

Gives a useful overview of the gradual (pre-IAU) re-classification of Ceres, Pallas, Juno, Vesta and so on that occurred during the 19th century.

The BAJ and the Paris Observatory accorded Ceres through Vesta a form of 'dual citizenship' with both the planets and the asteroids through the mid-1860's. The failure of this dual categorization is noteworthy because Ceres, the first asteroid discovered, is estimated to contain 30-40% of the mass of the asteroid belt, while Pallas and Vesta combined are nearly as massive as Ceres. Because they fit the mold of a minor planet better than that of a regular planet, even these largest asteroids are considered minor planets after more than 50 years of being accepted as planets like Jupiter, Saturn, and Mercury.

[SFJCody]

For the record, I'm on the side of disowning the word 'planet' and coming up with something better. But I'm prepared to accept 8, 10 or 20+ planets in the interim. Just not 9.

[dvandorn]

I think the trick here is going to be in the sub-classifications. These sub-classes already exist in the "taxonomy" of a solar system -- we just need to tighten up the definitions.

Maybe a nice, tidy system such as this:

Planets -- bodies made spherical by self-gravitation and that orbit the Sun primarily (i.e., do not have another body as its orbital primary)

Rocky planets -- includes Earth, Venus, Mercury & Mars

Dwarf rocky planets -- includes Ceres, Vesta, any others to be discovered

Gas giant planets -- includes Jupiter and Saturn

Icy planets -- includes Uranus and Neptune

Dwarf icy planets -- includes Pluto and any other KBO / TNO that meets the initial requirement of being a planet in the first place

I guess you could call the "dwarf" varieties something else, like "minor planets" or "planetoids," but I like dwarf better. Not only is the term more in keeping with established astronomical nomenclature, but with the amount of gravitational adjustment their orbits have probably undergone, you could say that the Solar System is engaged in "dwarf tossing"...

-the other Doug

[SFJCody]

http://www.boulder.swri.edu/ekonews/issues...html/index.html

http://www.gps.caltech.edu/~mbrown/planetl...ndex.html#paper

[Guest_Myran_*]

David said: Australia is actually a good comparison to Pluto

Interesting way of putting it, but I really dont think so. Lets see. Asia would be Jupiter then, bigger than the rest. Yet we would end up with Australia being a terrestrial planet lets say Mercury since both are hot and reserve Antarctica for Mars. So we will have Greenland or Madagascar for Pluto then.

Thats true dvandorn, we have dwarf stars and dwarf galaxies. But those are bona fide object with internal fusion in the first case and true system of stars where stellar nurseries create new stars etc, perhaps at a very low pace but they still do.

The term 'dwarf planet' would suggest the object are a true member of the planetary albeit small. Yet I still cant say that it feels right putting label of 'dwarf planet' on everything from Chiron, Pluto, Vesta and Ceres.

Mr Kupiers theory that planetary formation would leave a belt of objects outside the set of regular planets have turned out to be correct. We have found plenty of those now.

If current theorys are to be trusted, these could be the let over building blocks that actually made the regular planets. And anyone in the right mind wouldnt declare a brick to be a house.
With the exception of something really huge size doesnt matter.
Yet if we would find lets say an object like Neptune out in the Kupier belt, I would have no problem naming that a planet, since it would be mostly gaseous with a small solid and liquid core and not be of the same kind as the other KBO's.

[SFJCody]

There's a paper at http://harbor.scitec.kobe-u.ac.jp/~patryk/patryk-bigTNOs.pdf

that looks at the relationship between size and albedo for the big TNOs (the larger ones seem to have more extensive frosts than the smaller ones). Plugging in the the details of the new objects to the equations on page 5:

Designation, H, est diameter (km) + / - est albedo + / -


2003 UB313 -1.2 2680 60 80 0.74 0.05 0.03

2005 FY9 -0.3 2180 90 140 0.49 0.07 0.04

2003 EL61 0.1 1990 100 150 0.41 0.07 0.04

(90377) Sedna 1.6 1420 110 180 0.20 0.06 0.03

[ljk4-1]

Paper: astro-ph/0508633
Date: Tue, 30 Aug 2005 01:01:01 GMT (25kb)

Title: Discovery of a planetary-sized object in the scattered Kuiper belt

Authors: M.E. Brown, C.A. Trujillo, D.L. Rabinowitz

Comments: 9 pages, 1 figure
\\
We present the discovery and initial physical and dynamical characterization
of the object 2003 UB313. The object is sufficiently bright that for all
reasonable values of the albedo it is certain to be larger than Pluto.
Pre-discovery observations back to 1989 are used to obtain an orbit with
extremely small errors. The object is currently at aphelion in what appears to
be a typical orbit for a scattered Kuiper belt object except that it is
inclined by about 44 degrees from the ecliptic. The presence of such a large
object at this extreme inclination suggests that high inclination Kuiper belt
objects formed preferentially closer to the sun. Observations from Gemini
Observatory show that the infrared spectrum is, like that of Pluto, dominated
by the presence of frozen methane, though visible photometry shows that the
object is almost neutral in color compared to Pluto's extremely red color. 2003
UB313 is likely to undergo substantial seasonal change over the large range of
heliocentric distances that it travels; Pluto at its current distance is likely
to prove a useful analog for better understanding the range of seasonal changes
on this body.

\\ ( http://arXiv.org/abs/astro-ph/0508633 , 25kb)

[volcanopele]

NO, NO!!!!!  That [extremely bad word] proposal -- to call Pluto a planet but 2003 UB313 not a planet, despite the fact that it's BIGGER than Pluto -- has also been pushed by (I believe) Penelope Boston.  NOTHING could confuse schoolkids and the general public more than this about the real nature of the Solar System.  This proposal isn't just scientifically doubtful; it's flat-out INSANE!

I absolutely agree. To call Pluto a planet and not 2003 UB313, an object larger than Pluto, is downright moronic I agree, the term "planet" really can't be scientifically defined if we set arbitrary limits, but any proposal that includes Pluto and not 2003 UB313 is absolutely unacceptable.

[Guest_Myran_*]

Moronic? Perhaps I am.
While on the other hand, declaring 2003 UB313 a planet would necessitate the rewriting of every astronomical textbook back to the 19'th century.
We already have one systematic approach how to label various objects within the solar system. Planets, moons, comets, rings and yes belts. I see no reason why we should throw all that overboard.

[volcanopele]

Moronic? Perhaps I am.
While on the other hand, declaring 2003 UB313 a planet would necessitate the rewriting of every astronomical textbook back to the 19'th century.
We already have one systematic approach how to label various objects within the solar system. Planets, moons, comets, rings and yes belts. I see no reason why we should throw all that overboard.

Sorry, moronic is perhaps not the best word, but to me, it makes no sense to call Pluto a planet and 2003 UB313 not a planet. If one wants to downgrade Pluto, fine, while I disagree, it makes more sense than having a minor planet that is larger than a full-fledged one.

Personally, I have no problem with re-writing textbooks or over throwing centuries-old schemes if the data calls for it. And I don't think adding a planet really changes much.

[Guest_Myran_*]

Dont worry volcanopele, it provided me the opportunity for some self bashing on my part. I picked my nick already from the start knowing that I would be one ant among giants on this forum.

Its all obvious that you base your view on that of size, whereas I tend to view objects as belonging to different groups. Yes had my life taken a different path I certainly could have ended up as one beancounter.

So I cant help thinking that it does matter, since its a deviation from the established system of classification. Even though the idea of the Kupier belt have been only theory during the most part of my lifetime, we now have established its existence. And in the future we might find the objects of the Oort cloud as well, for me it would simply be one addition to the cometary family of objects - again regardless of size. Lets say one of Plutos size were found out there, to me it would just be 'the motherload of all comets'.
With my way of reasoning Pluto would indeed be at risk of loosing the planetary status, yet I mentioned one way to avoid that earlier if IAU would so decide.

Since my culture are known for our ability to make compromises, I offer you the compromise that we are all free to disagree on this matter.

[antoniseb]

With my way of reasoning Pluto would indeed be at risk of loosing the planetary status

I haven't read your previous statement on this, so perhaps I am mostly just agreeing with you.

This issue of whether Pluto or 2003 UB313 should be considered planets seems kind of old-fashioned. We know information about a quarter million things which orbit the Sun, including estimates of how big they are and guesses of what they are made of. We never have to say whether Pluto, or Sedna, or 2003 UB313, or Ceres is a planet. We simply identify the object as needed for whatever purpose. So far, no one will have their real estate drop in value because Pluto loses some linguistic status.