IAU Proposes 3 New Planets

IZ Reloaded writes "Sources tell SPACE.com that the International Astronomical Union is preparing to include three new entries to the current list of planets in our solar system. From the article: The asteroid Ceres, which is round, would be recast as a dwarf planet in the new scheme. Pluto would remain a planet and its moon Charon would be reclassified as a planet. Both would be called "plutons," however, to distinguish them from the eight "classical" planets. A far-out Pluto-sized object known as 2003 UB313 would also be called a pluton."

Comments

Re:What the pluton?

[Kryis]

A rose by any other name would smell as sweet

Why?

[DarkNemesis618]

Wouldn't it simply be easier just to have the nine
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto

I mean its been that way for years...just classify those other things as whatever you want to call them.

Re:Why?

[Anonymous Coward]

It's been that way only since Tombaugh found Pluto in 1930.
And before, Ceres Pallas and Vesta have all been considered as planets until it was clear that they were part of something else : the Asteroid Belt.

Here I'd say stay with the same logic and consider Pluto as an asteroid.

Re:Why?

[Adhemar]

I completely disagree with that the current system is better, but I don't see why your question merits the moderation (-1, Troll).

It's completely unsatisfactory to talk about "planets" when we don't know what is meant by a planet. Simply enumerating the ones in our solar system makes it very clear for our system, as we did so far, gives clarity for our solar system: the nine ones are planets, all others aren't. It doesn't state a reason. If asked why Pluto is a planet, and the very similar 2003 UB313 ("Xena") isn't, all we can say is: "historical reasons" or "convention".

When describing other solar systems, it is very normal to describe celestial bodies which are similar to the planets of our solar system, as "planets". But when is a body sufficiently like a planet of our own, to merit this description?

Really, it was high time we got a workable definition. Anything. Anything is better than an enumeration.

So, the International Astronomical Union (IAU) currently holds a highly-anticipated conference on the definition in Prague. It started last Monday, and a final decision is expected by next Thursday August 24, 2006.

The current proposal is:

A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet.

It has the added benefit that the minimum size (to exclude most Kuiper belt objects etc.) is not an arbitrary number, but a physical condition. The shape of objects with mass above 5 × 10^20 kg and diameter greater than 800 km would normally be determined by self-gravity. In borderline cases, we now must observe the roundness.

The pluton definition does have an arbitrary figure in its proposed definition: orbits around a star that takes longer than 200 years to complete.

Re:One issue

[Profane MuthaFucka]

Part of the definition is that a planet has sufficient gravity to make it into a round-ish shape. You can't jump off any body that has enough gravity to accomplish that.

Re:Sheesh

[plasmana]

We need a planetary definition so we can communicate efficiently. Why else do we need words. Try talking about your environment without classifications of natural objects:

I bought my direct ancestral animated entities an animated entity with four appendages used for walking, one appendage for knocking down lamps, a soft covering that is white with black spots, which speaks in guttural exclamations which are just nonsensical to animated entities like myself.

Instead of:

I bought my kids a dog

As our observations of our environment reveals new information. We must periodically change our definitions to attempt to make our abstractions best reflect reality.

Because

[Silver Sloth]

Science is always about testing the hypothesis against the data and redefining as required. You might as well say 'why don't we have four elements 'earth, water, air and fire', it's been that way for years.

If you're going to do science then you have to live with knowledge changing.

Bureaucratic silliness

[Carmelbuck]

This, unfortunately, is what happens when you try to wrap a scientific definition around a cultural concept. It seems pretty clear that the simplest and most logical option (demote Pluto) was deemed unpalatable to the general public. Which, really, is what this is all about; solar system research will go on the same regardless of what the things are being called. Since the textbooks will be rewritten anyway, why go for such an unwieldy change? No one now cares that Ceres, Pallas, Juno, and Vesta were all initially designated as planets before their nature was realized and the term "asteroid" was coined; I suspect that if Pluto were redesignated then its former status would likewise be forgotten in a few decades.

In any case, let's note that this isn't official yet; it will be voted on at the IAU symposium in the next couple of days. Let's hope that enough present have the good sense to send this back to committee.

Re:One issue

[geobeck]

But according to an article by Isaac Asimov (Just Mooning Around from Of Time and Space and Other Things), the Sun pulls the Moon twice as strongly as the Earth does, and the Moon's orbit, drawn to scale, is always concave toward the Sun, making a very convincing argument that the Earth and the Moon are a double planet system, even though their center of revolution is a thousand miles beneath the Earth's surface.

If Charon is to be classified as a minor planet, the Moon should be too.

Slight modification

[phlegmofdiscontent]

The term "dwarf planet" is actually starting to grow on me. It still keeps Pluto as a planet, for those who absolutely need it to be a planet, but really it IS a demotion to a status equal to the larger asteroids & KBOs. The way I see it, the Solar System has 8 Major Planets (4 terrestrial, 4 gas giants), at least 50 Dwarf Planets (Pluto, Ceres, 2003 UB313, etc) that are round due to self-gravitation, and the non-round objects can still be called Minor Planets. It just adds an intermediate classification between "planet" and "asteroid/minor planet".

Re:What the pluton?

[Andy Somnifac]

The "debate" is basically a media event, based on people who take their grade-school science classes too seriously, and think that for some reason that the Solar System must contain exactly nine "planets".

I think that one of the problems in this country (the US) is that we do not take grade school science seriously enough. We need those science classes to engage the kids and hopefully inspire some of them to a career in some scientific field.

Why not the obvious scheme?

[Anonymous Coward]

Any object as big or bigger than those we can see with the naked eye from Earth is a planet. Any object smaller than that isn't. That's entirely anthropocentric, of course, but so is the need to classify solar system objects in the first place.