Sedna

Originally posted by ivan_2068


Well Yesspaz, the orbit of a comet is absolutely different to the orbit of a planet, it's not heliocentic because it crosses the orbits of other planets, the orbit of a planet is almost perfectly heliocentric and independant to other plamets, unless something really catastrophic happens).

Of course the comets have other features that planets don't have like tail, nucleus, coma, etc.

Iván

Pluto IS a planet and it's orbit crosses that of Neptune. I think that at the moment or at least until recently Neptune was the furthest planet from the sun.

[moses]

Pluto IS a planet and it's orbit crosses that of Neptune.

Well, Gustav Holst crosses the orbit of Emerson, Lake and Powell, King Crimson, and possibly others.

[Rick and Roll]

Neptune's just weird, with the way it spins, etc. I think we should impeach Neptune.

And can we have a planet Goofy if we have a Pluto? Oh yeah, that's Earth.

[Yesspaz]

There are many qualifications to make something a planet. Crossing orbits or not is not one of them (good call KW). The meteor belt between Mars and Jupiter fits that scenario, but thier not planets. All I'm saying is that there are many criteria. I don't know them all. While I think it'd be super-cool if Sedna is a planet, I think the scientists are correct to be cautious and wait and see for sure, doing more research.

[Roger -Dot- Lee(Admin)]

Originally posted by Yesspaz
There are many qualifications to make something a planet. Crossing orbits or not is not one of them (good call KW). The meteor belt between Mars and Jupiter fits that scenario, but thier not planets. All I'm saying is that there are many criteria. I don't know them all. While I think it'd be super-cool if Sedna is a planet, I think the scientists are correct to be cautious and wait and see for sure, doing more research.

While I'm all for scientific prudence and all, my biggest question is: what's the difference? Is it going to affect anything at all if it's considered a planet or an Oort Cloud Object or perhaps Jimmy Hoffa's Final Resting Place? Will it affect the research that's done on it? Or will it just totally bugger up all the Astrological charts that have been drawn up for centuries?

If there's a sound scientific reason for it, I suppose it's OK (like they need MY permimssion ) but it just strikes me as a whole lot of arm waving and histrionics for nothing.

Am I missing something?

[Rick and Roll]

I'm sure it's important to the ones dealing with and classifying such things. Sort of like me trying to explain the difference between a Controller and a Comptroller.

I do agree about classifications - my #1 beef when discussing music................

[Yesspaz]

Originally posted by Roger Lee


my biggest question is: what's the difference?

I think the difference is that planets have a certain status that's different than other objects. Elementary school students learn the names of the nine planets. They don't learn about Oort Cloud objects or the dozens of comets. They don't learn the names of the asteroids or the names of the many moons. Planets have some sort of mystical ascribed status.

In other words, it's totally freaking cool to say, "We've got a tenth planet!" It's not so cool to say, "We've got a 35th Oort Cloud Object!"

[ivan_2068]

Pluto IS a planet and it's orbit crosses that of Neptune

Agree Yesspaz didn't remembered Pluto's weird orbit, but at least is mostly heliocentric.

In other words, it's totally freaking cool to say, "We've got a tenth planet!" It's not so cool to say, "We've got a 35th Oort Cloud Object!"

Agree with that.

Iván

when the minor planet Chiron was discovered between Saturn and Uranus. It was widely believed that this was either a dead comet ot the brightest of a group of asteroids between Saturn and Uranus. I sort of lost touch a bit on that one.

btw. It's got a bit confusing for the mildly dyslexic when they named Pluto's satellite Charon.

[Yesspaz]

Originally posted by Keith Waye
the minor planet Chiron was discovered between Saturn and Uranus

huh? man, how did I miss this one? Info Avian!

[ivan_2068]

Chiron is a minor body discovered by Charles Kowal based on fotographs on 18 and 19 October 1977.

From the start it was almost certain it wasn't a planet or planetoid In 1988 a tail was observed, indicating was a comet bigger than anyone seen before.

Chiron, discovered in 1977, is an unusual object whose highly-elliptical, 50-year orbit around the sun brings it within the orbit of Saturn and as far out as the orbit of Uranus. It exhibits properties of both a comet (it has a coma) and an asteroid (it is as big as a large asteroid -- some 200 km in diameter -- much larger than the biggest known comet), so it has been designated as one of a class of objects known as Centaurs. These half-comet/half-asteroid objects were named after the mythical half-man/half-horse; Chiron is named after the wisest of the Centaurs. Several objects in this class have been discovered; they may be objects that have escaped from the Kuiper belt, the vast disk of cometary bodies beyond the orbit of Neptune. Chiron is designated alternately as Comet 95P/Chiron or minor planet (2060) Chiron.
http://pages.prodigy.net/pam.orman/j...eArticle2.html

Iván

[Avian(Admin)]

Originally posted by ivan_2068


Well Yesspaz, the orbit of a comet is absolutely different to the orbit of a planet, it's not heliocentic because it crosses the orbits of other planets, the orbit of a planet is almost perfectly heliocentric and independant to other plamets, unless something really catastrophic happens).

Of course the comets have other features that planets don't have like tail, nucleus, coma, etc.

Iván

The orbits of most comets are most DEFINATELY heliocentric (they orbit the sun). The fact that their perihelion (closest approach to the sun) is inside the orbits of the other planets doesn't mean anything. Long period comets are in highly elliptical orbits, their periods being measured in many decades - some in millenia. Some comets eventually break up completely after repeated trips to the inner solar system, if they come in that far.

Some planets have very circular orbits like the earth, others are more elliptical, like Pluto (and certinaly Sedna).

More information about Chiron and the Centaur objects can be found here.