Debate hope to pin down what defines a planet

Sonia · #1 31-07-2006, 02:43 AM

A heated debate over what defines a planet comes to a head this month at a meeting of the International Astronomical Union.
Astronomers have found many new worlds that are hard to classify: icy bodies beyond Neptune that don't seem big enough to be planets. Others are free floating bodies as big as Jupiter, with no parent star.
An an IAU meeting in Prague this month, astronomers are hoping to define what a planet is, something that could relegate Pluto's status.
A decision is expected in September.

jjjnettie (Jeanette) · #2 31-07-2006, 10:52 AM

I can see that there will be changes made, and there will be a percentage of people who will find that hard to take.

It'll be interesting to see what fallout occurs over the final decision.

Dujon · #3 31-07-2006, 11:31 AM

An interesting though, in my opinon, a total waste of talk time.

The few planets we have are already so varied. Rocky, atmosphere devoid through rocky with (varied) atmospheres and then to gassy failed stars. We have moons which would be termed planets if they orbited Sol in their own right instead of exhibiting a rather wobbly path due to their attraction to a larger body.

Whatever is decided is surely going to be an arbitrary line drawn in the solar system's sand. This could be based on composition or size or just about anything else (or combination with anything else) that we can dream up.

I reckon that until we know far more than we already do about our so called planets then leave the term alone. There's every chance that as we learn more our views will change.

ving (David) · #4 31-07-2006, 12:38 PM

yes, just what is a planet anyway? a body that orbits a sun, has an atmosphere, is a certain size, has a moon?

Adrian-H · #5 31-07-2006, 01:21 PM

the orginal definition of planet clearly states that all as long as its large, round and it orbits the sun its a planet, yet why do they call planetary nebular's "planetary" do they orbit the sun too? how come no ones complaining about planetary nebular's? hence there are alot of newer discoveries that defie many things.

this debate on defing "planet" is just as trival as debates of the va vinichi code defing churches. its merely just a "soical debate"

[1ponders] (Paul) · #6 31-07-2006, 04:01 PM

It is all a part of the evolution of astronomical science.

Originally "planet" as coined by the Greeks meant "Wanderer" and referred to any astronomical object that was not fixed in relation to the stars. Both the sun and the moon were considered to be planets once, along with the other 6 naked eye planets (though Uranus borders on the limit of visibility). It wasn't until Copernicus, Galileo and Kepler, that there was the first revolution in the meaning of "Planet" (although Aristotle did start it 2000 years before

). In fact it wasn't until the 1990's that the Church recanted their comdenation against Galileo for his heliocentric belief, that the planets orbited the sun and not the earth.

This current debate is just another step in that evolution.

#7 04-08-2006, 01:23 PM

Actually, it isnt the definition of the object that needs debating, it's the definition itself. The word "Planet" comes from greek and means "Wanderer", given to those celestial bodies that the ancients noticed moved or wandered around the skies. So given that information every object not "fixed" from earths perspective is a planet, including every rock in any belt out there. Now what we need to do is define the term, stop calling all of them planets and find a more fitting term that seperates large orbiting bodies from small ones. Time we updated the Astronomical distionary and put this BS to bed.

Gargoyle_Steve (Steve) · #8 05-08-2006, 03:29 PM

I'd like to see the definition of planets a little bit "better organised", but I think the notion that Pluto be de-classified as a planet is going the wrong way. Back off sci-guys, you're messing with history.

In my mind the "loose" definition should follow something like this : If an object is of sufficient physical size, and has sufficient mass and rotation to be basically spherical (ie if it's compositional strength is sufficient to support it's own mass without it falling apart); if it follows a well structured, elliptical orbit around the sun (and preferably not too outrageously elliptical, ie comets) and especially if it also has a moon or moons of it's own (new defiition for minimum size of moon needed too, pebbles don't count!) then it's got to be CLOSE to being a planet, hasn't it?

Result: Is Pluto a planet: YES, leave it alone damn it!!
Is 2003-UB313 a planet: Yes, & give it a real name then for cheese sake.
What about 2003-EL61 ?? Hmm ...... click the link, you decide.

All this thinking stuff is hard, I'm just here to look at the pretties.

Clear dark skies!

mickoking · #9 07-08-2006, 04:22 PM

A planet is anything bigger than Pluto

[1ponders] (Paul) · #10 07-08-2006, 05:16 PM

Quote:

Originally Posted by mickoking

A planet is anything bigger than Pluto

Hmmmm....I ain't touchin' that with a barge pole

ballaratdragons (Ken) · #11 07-08-2006, 05:26 PM

Quote:

Originally Posted by Adrian-H

the orginal definition of planet clearly states that all as long as its large, round and it orbits the sun its a planet, yet why do they call planetary nebular's "planetary" do they orbit the sun too? how come no ones complaining about planetary nebular's?

Adrian,

It's only because they have the visual appearance of Planets. They look roundish and sort of Planety. Not because they have any connection to the real term 'Planet'. It is only a descriptive term.

#12 08-08-2006, 11:07 PM

Quote:

Originally Posted by mickoking

A planet is anything bigger than Pluto

I reckon a planet is anything bigger than Uranus.

Now hang on a sec, If a planet is an orbiting body, then how big is the body of the gas giants?? You can not include gas as the body. Could be they are smaller than pluto, geeeez, back to the drawing board. Wait, I have it, they must be palnetry nebula. Iv'e come full circle, or is that an orbit?

Reading between the lines of my posts, can you tell I just dont take this argument seriously? What a nonsense.

Adrian-H · #13 09-08-2006, 07:22 AM

Quote:

Originally Posted by ballaratdragons

Adrian,

It's only because they have the visual appearance of Planets. They look roundish and sort of Planety. Not because they have any connection to the real term 'Planet'. It is only a descriptive term.

so tell me, whats the differance between describling something as a planet, and calling something a planet?

and whats the benefit of wasting so much money,power and time over a definition?

IanW · #14 14-08-2006, 05:50 PM

A fun read about the debate:

http://www.guardian.co.uk/space/arti...844050,00.html

Ian

Argonavis (William) · #15 16-08-2006, 09:03 AM

Although the debate has yet to be finalised, it seems likely that Pluto (and Xena) will be planets number 9 and 10, based on the fact that they orbit the Sun, have sufficient gravity to be spherical, and are above an absolute magnitude filter.

see:
http://astro.cas.cz/nuncius/nsiii_02.pdf

and maybe we will get planets numbers 11, 12, 13, 14 and 15 using the same definition. (Charon, Ceres, Vesta, Pallas, KBO EL61)!!!!

Of course, this is not really astronomical science - the people who study these objects probably don't care whether they are planets, minor planets, planetismals, KBO, TNO, asteroids, or whatever you call them does not alter their physcial characteristics. Just as there are no boring galelian moons there is undoubtedly no boring KBO's, I suspect they will all be very different. The close up spacecraft views we have of asteroids and comets so far captured would indicate an intrigueing diversity of surface features.

waste of time really - just call them all minor planets