[X] My Assistant

[Guest_Kevin Heider_*]

I had assumed that 1 Ceres was still considered an Asteroid since it orbits in the asteroid belt and has the same origin as the other asteroids.

But I noticed that on wikipedia they say: "Ceres is a 'dwarf planet', and may no longer be classified as an asteroid."

Wikipedia cites the IAU website at http://www.iau2006.org/mirror/www.iau.org/...u0603_Q_A2.html that states:
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Q: What is Ceres?

A: Ceres is (or now we can say it was) the largest asteroid, about 1000 km across, orbiting in the asteroid belt between Mars and Jupiter. Ceres now qualifies as a dwarf planet because it is now known to be large enough (massive enough) to have self-gravity pulling itself into a nearly round shape. [Published reference for shape of Ceres: P. Thomas et al. (2005), Nature 437, 224-227. Dr. Peter Thomas is at Cornell University.] Ceres orbits within the asteroid belt and is an example of a case of an object that does not orbit in a clear path. There are many other asteroids that can cross the orbital path of Ceres.

Q: Didn’t Ceres used to be called an asteroid or minor planet?

A: Historically, Ceres was called a “planet” when it was first discovered (in 1801) orbiting in what is known as the asteroid belt between Mars and Jupiter. Because 19 th century astronomers could not resolve the size and shape of Ceres, and because numerous other bodies were discovered in the same region, Ceres lost its planetary status. For more than a century, Ceres has been referred to as an asteroid or minor planet.
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Is Ceres still classified as an asteroid since it is located in the asteroid belt? Pluto is a Kuiper Belt Object (KBO) even though it is also a 'dwarf planet'.

Has Pallas become the 1st asteroid discovered? Has Vesta become the largest asteroid (at least until the IAU decides that since Vesta is a damaged, differentiated protoplanet that it was probably spherical in the past)? *IF* Ceres is truely no longer an asteroid, because it is spherical, then those two very basic questions have new answers!

How do we contact the IAU for an official statement on the classification of Ceres as an asteroid?

-- Kevin Heider

[djellison]

Don't ask the IAU - they don't have a clue what they're doing

Under their rules, Pluto is a Dwarf Planet but no one would deny it's still a Kuiper Belt object. I think it's just a venn-diagram overlap of 'Dwarf Planet' and 'Asteroid' where you'll find Ceres.

Becaus a couple of dozen people held up a particular coloured card in a conference room - suddenly Ceres stops being an asteroid? That's just moronic. It remains a member of the asteroid belt.

That is the pivotal idiocy of all this nonsesne..Pluto is still Pluto and Ceres is still Ceres. One is still a KBO and one is still an Asteroid. If you also decide to classify them as Dwarf Planets or Planets or anything....they're still a KBO and an Asteroid. Whoever decided to try and claim, via Wikipedia, that Ceres is not an asteroid is an idiot.

Doug
(PS - I would be very very wary use Wikipedia as a source of fact or reliable information)

[edstrick]

The FUNDAMENTAL problem is that the term "Planet" is of pre-scientific origin, and has been adapted on an "everybody knows what a planet is" basis over time as it's use has been "upgraded" during the evolution of of post-telescopic Astronomy.

Definitions tend to split between Descriptive, and Genetic. That's the ultimate schizoid origin of the battle. Io and Titan are planets - - - geologically. But not in genesis. The standard definition evolved to assume planets formed in solar orbit, but moons accreted in planetary orbit... but captured objects?.... should they be defined as moons?... Triton WAS a dwarf planet before it got captured by Neptune....

I consider the whole thing "spectator sport". It's important, but not IMPORTANT... if you get my drift.

[helvick]

I consider the whole thing "spectator sport". It's important, but not IMPORTANT... if you get my drift.

I agree. Time will tell how it works out I suppose and in the mean time we can but watch.

For me I can't see why the term "planet" can't be applied happily to anything that is simply big enough - the hydrostatic/gravitationally spherical thing - provided it isn't actually a stellar or post stellar obect. Then you prefix whatever modifiers that suit the required set:
Classical ("Greek") planets: Everything out to Saturn but excluding earth.
Traditional planets: The "9" including Pluto.
Real or Giant planets: Jupiter, Saturn, Uranus, Neptune (Gotta be BIG to be Real!)
Gas Giant planets: Jupiter, Saturn
Ice Giant planets: Neptune, Uranus
Terrestrial planets: Venus, Earth, Mars, Titan (Rock balls with an atmosphere)
Rock planets: Any planet made primarily of rocks (Mercury, Luna...)
Ice planets: Any planet made of Ice (Pluto, Europa)
Dwarf planets: Pluto, Charon, Eris (The IAU can have this one, OK by me)
Lunar planets: Mercury, Luna, Ceres, Vesta, Charon, Ceres, Eris, Triton,Ariel, Umbriel, Titania, Oberon, Tethys, Dione, Rhea, Iapetus, Io, Europa, Callisto, Ganymede .. (any >1000km and < 5000km diameter body with no significant atmosphere)
Satellite planets: Any planet that is in orbit around another planet.
Minor planets: All the Lunar planets + Dwarf Planets
Red planets: Reddish\Brown ones (like Mars, Io, Titan and Pluto)
Blue planets: Blueish ones (Earth, Uranus, Neptune)
Lonely planets: Ones that are waay out in the void on their own.
Hellfire planets: Hot Jupiters.
etc.

Edited to add:
Apologies to any large round spherical bodies I may have missed - you can have the title:
Forgotten planets.

Clearly I personally don't have an issue with having oodles of planets. As I see it we know for certain now that there are billions of them around other stars so adding as many to our own system seems only fair to me.

Share and enjoy!

[angel1801]

I would assume (unless the IAU says otherwise) that Ceres is both an asteroid and a dwarf planet at the same time. Of course, the IAU may say some something about this in 2009 at their next General Assembly.

[alan]

Has Pallas become the 1st asteroid discovered? Has Vesta become the largest asteroid (at least until the IAU decides that since Vesta is a damaged, differentiated protoplanet that it was probably spherical in the past)? *IF* Ceres is truely no longer an asteroid, because it is spherical, then those two very basic questions have new answers!

No, if you can't use the new categories to Ceres only, you need to apply them to the other members of the asteroid as well. In that case the other members are small solar system bodies, asteroids no longer exist.

Actually the legacy categories identify the locations of the objects, I don't see any conflict in continuing to use them.

[Jyril]

Ceres is still an asteroid. The terms 'asteroid' and 'minor planet' will stay in use.

(3) All other objects[3] except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

[3] These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

Note the two "mosts": Ceres is an asteroid, Pluto and Eris are TNOs, but none of them is an SSSB (because all of them fulfill the definition of a dwarf planet).

[ElkGroveDan]

(PS - I would be very very wary use Wikipedia as a source of fact or reliable information)

I was going to make that caution when the Wikipedia issue came up in another thread yesteday. Worse, people with an ax to grind are able to simply change entires at will, and then a battle of semantics erupts.

So if anyone doesn't like the Ceres entry go ahead and change it, but be sure to back up your assertions with facts and citations. The Wiki administrators love cites. If you can provide a cite, to them it becomes truth.

[Jyril]

The Wiki administrators love cites. If you can provide a cite, to them it becomes truth.

Cites make claims verifiable, not truth. You must realize that Wikipedia is an encyclopaedia, not a scientific work. It is a collection of information and is always dependent on other sources which may not be accurate (like the CIA "fact"book). This is true with all encyclopaedias. Often only a real expert can say if a source is credible or not. Wikipedia editing system is especially problematic since even totally clueless users can contribute. It was especially frustrating in the case of Eris (then 2003 UB313) article; people kept (and still keep) adding the cursed X-word into the article despite it was already mentioned there.

[Mariner9]

edstrick said it best: 'planet' is a term that predates our current scientific knowledge of solar system objects.

Since 'asteroid' also is from a fairly early time, I think that word falls into the same catagory.

I think any attempt to force a firm scientific definition onto 'planet', 'asteroid' and even 'comet' is ultimately doomed, and counterproductive.

We should just leave those words as the 'common man's vernacular' and let the scientific world come up with terminology that suits the evolving understanding of our cosmos.

If people want to get down to the nitty gritty, what about earth crossing 'asteroids' whose orbits don't even get out to the main belt? What about extinct comets that still remain in their elliptical orbits, but no longer form a coma? And when does something get so small it is no longer an asteroid, but just a meteoroid?

Ugh. Trying to sort it out with non-scientific terminology is just too annoying.

My vote (which doesn't count with the IAU) is to leave Ceres an asteroid, because it is obviously in the asteroid belt.

[edstrick]

Another term, one I actually hope gets adopted, is ROGUE PLANET, a planetary object in interstellar space (dynamically), unbound to any star (or brown dwarf). The term had a history in fairly early science fiction, and I think was used in the 1950's TV SF series like Rocky Jones, Space Ranger. The Oxford English Dictionary's science fiction terminology project should have the earliest documented -- so far -- occurrence of the phrase.

[Rob Pinnegar]

Another term, one I actually hope gets adopted, is ROGUE PLANET, a planetary object in interstellar space (dynamically), unbound to any star (or brown dwarf).

It probably will get adopted eventually. Although the dictionary definition of "rogue" doesn't really match the description, "rogue planet" has the advantage of having few syllables.

It is also just unambiguous enough to be workable. My guess is that, if you were to ask the average person on the street what a "rogue planet" is (and told them that they weren't allowed to describe it in terms of alien civilizations on Star Trek), a good-sized percentage would come up with the idea of a planet unbound to a star, probably describing it as "a planet flying uncontrollably through space" or something like that. So it's pretty intuitive.

If anyone in the astronomical community doesn't like it and thinks something else would be more appropriate, they had better start pushing their idea now -- and it'd be a good idea to come up with something less cumbersome than "Small Solar System Bodies" (a good example of nomenclature that is clear, unambiguous, and will likely be used by just about nobody).

[Stephen]

I had assumed that 1 Ceres was still considered an Asteroid since it orbits in the asteroid belt and has the same origin as the other asteroids.

But I noticed that on wikipedia they say: "Ceres is a 'dwarf planet', and may no longer be classified as an asteroid."

Hmm. If asteroids no longer exist (because they have all metamorphosed into "dwarf planets" and "small solar system bodies") that raises the question of whether Kuiper Belt Objects (KBOs) have vanished from the astronomical lexicon as well.

And what about comets? Are we now supposed to talk about "Halley's Small Solar System Body"?

"(3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as 'Small Solar System Bodies'."

--http://www.iau.org/Resolutions_5-6.398.0.html

It seems they have been abolished. Along with "meteors", "meteoroids", "meteorites", "cosmic dust", etc etc.

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Stephen

[Jyril]

Asteroids no longer exists!? What happened to them?

You are mistaken. The Small Solar System Body is an umbrella term which includes all objects other than the Sun, planets and dwarf planets.

The terms 'asteroid' and 'minor planet' will continue in use. The original definition draft would have removed the term 'minor planet'. But since the term has been used 150+ years, it was deemed stupid to scrub it.

[djellison]

Minor planet would make a lot more sense than 'dwarf' planet - but neither is appropriate for a class of body that hasn't 'cleaned up' it's area. That would be like calling anyone who lives in a block of apartments a dwarf human.

Doug