30-07-2005 03:08									#1
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http://www.newscientist.com/article.ns?id=dn7758

Cool.

I wonder how many of those Kuiper belt objects are around there, anyway?

	30-07-2005 03:19									#2
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IM sure thousands of pluto and below sized planet-(oids) .. the thing is, most of them probably don't come anywhere as near as pluto, and if they are on eliptical orbits, they may only venture close enough to be detected every few thousand years.

	30-07-2005 03:26									#3
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I don't know why, But I like the little buggers very much.

So now, Quauauauaor, Pluto, Sedna, and this new kid.

cool

	30-07-2005 03:30									#4
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These new objects being discovered really put Pluto down as a non-planet IMO.

	30-07-2005 03:34									#5
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How have we defined planet, again? a big spheric lump of matter with a diameter larger than a certain arbitrary size?

Then yes. If we define, say 2000 miles in diamtere. but then Luna is a planet ( I agree with this, btw)

	30-07-2005 03:35									#6
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It has to orbit the sun, does it not...

	30-07-2005 03:42									#7
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a) a sun, not necessarily sol.
b) I don't agree with that, either. I think that if it's pretty huge, round, and isn't a has-been star, or an actual living star, it's a planet.

	30-07-2005 03:47									#8
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Our sun is a type two star. The Earth is made from heavy elements that were created from a type one star that went nova or collapsed a while ago. Therefore, according to your opinion we don't live on a planet...

	30-07-2005 03:50									#9
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by "has been star" I wasn't referring to nova debri, but to white dwarfs, neutron stars, and crap like that.

	30-07-2005 03:54									#10
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quote: Originally posted by Az How have we defined planet, again? a big spheric lump of matter with a diameter larger than a certain arbitrary size? Then yes. If we define, say 2000 miles in diamtere. but then Luna is a planet ( I agree with this, btw)

I would'nt have a definition as such, just take each instance, individually and asses (sp) it.

To me Pluto loses out on it size and it's eliptical orbit.

If Pluto is a planet then why not Charon? they orbit a common centre of gravity that, unlike the Earth and the Moon, is actually outside the larger body.

	30-07-2005 03:58									#11
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They're a binary planet.

Agreed. while I don't think that the orbit has anything to do with it ( again, I don't like tying planets to circling suns ), Pluto isn't a planet. It's just too damn small.


Btw, previously I stated Sedna is a Kuiper Belt object - this isn't the case.

	30-07-2005 05:19									#12
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Luna does orbit the Sun.

	30-07-2005 07:12									#13
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quote: Originally posted by Az How have we defined planet, again? a big spheric lump of matter with a diameter larger than a certain arbitrary size? Then yes. If we define, say 2000 miles in diamtere. but then Luna is a planet ( I agree with this, btw)

I think the diameter of Mercury is a convenient (if arbitrary) cut-off point, large enough so we don't eventually end up with two dozen Kuiper Belt objects labeled "Major Planets"

	30-07-2005 07:14									#14
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quote: Originally posted by Az How have we defined planet, again? a big spheric lump of matter with a diameter larger than a certain arbitrary size? Then yes. If we define, say 2000 miles in diamtere. but then Luna is a planet ( I agree with this, btw)

I'd say that it has to contain within it the center of mass of it and all other objects sharing its orbit - to eliminate moons.

	30-07-2005 11:56									#15
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I thought anything large enough to be spherical under its own gravity and circling a star in its own orbital plane was a planet. This definition excludes comets, asteroids, moons, and Kuiper belt objects.

Kuiper Belt objects, like a large asteroid, has not cleared out its orbital plane (think early Earth). So it is considered part of the belt for now. Pluto is seperate from the belt so it can be considered a planet.

A moon orbits a planet. Many moons can qualify as a planet but they would have to orbit a star instead of a planet.

	30-07-2005 12:28									#16
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Calling the Moon 'Luna'.

	30-07-2005 12:43									#17
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There are many moons. Luna seems like a great name for the moon of our planet.

quote: I thought anything large enough to be spherical under its own gravity and circling a star in its own orbital plane was a planet. This definition excludes comets, asteroids, moons, and Kuiper belt objects.

Again, I don't think it's a fair definition. what about planets that are left behind disappearing stars? are they not planets anymore?

	30-07-2005 14:48									#18
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quote: Originally posted by Az Again, I don't think it's a fair definition. what about planets that are left behind disappearing stars? are they not planets anymore?

Of course not, they are no longer orbiting a star. I'm not sure what they are called in that instance (a rogue planetoid comes to mind).

I'd be more concerned about why those stars are disappearing.

	30-07-2005 15:09									#19
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quote: Of course not, they are no longer orbiting a star.

Well, I disagree.

quote: I'd be more concerned about why those stars are disappearing.

Not necessarily disappearing completely but possibly losing enough mass so that the planets aren't orbiting them ( after the creation of a nebula, for example )

	30-07-2005 15:17									#20
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quote: Originally posted by Az quote: Of course not, they are no longer orbiting a star. Well, I disagree.

That's okay. The definition is vague enough to make us both right (or wrong).

	30-07-2005 15:18									#21
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You could probably get a situation where a red dwarf (star) is orbiting a pair of brown dwarfs (planets... kinda).

	30-07-2005 15:24									#22
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quote: Originally posted by Sandman Calling the Moon 'Luna'.

Agreed. Very pretentious

	30-07-2005 15:32									#23
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quote: Originally posted by Sandman You could probably get a situation where a red dwarf (star) is orbiting a pair of brown dwarfs (planets... kinda).

Brown dwarfs stretch the definition even further. Extra large planets can be considered failed stars so your example could also represent a trinary system.

	30-07-2005 16:06									#24
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IIRC, that wouldn't include the center of mass in either between the planets, or in the star, making it a tertiary system.

	30-07-2005 16:13									#25
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quote: Originally posted by Vince278 Brown dwarfs stretch the definition even further.

Hmmm....


Brown dwarf in the ring
Tra la la la la
There's a brown dwarf in the ring
Tra la la la la la
Brown dwarfl in the ring
Tra la la la la
She looks like a sugar in a plum
Plum plum

Show me your motion
Tra la la la la
Come on show me your planetary motion
Tra la la la la la
Show me your planetary motion
Tra la la la la
She looks like a sugar in a plum
Plum plum

	30-07-2005 16:27									#26
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quote: Brown dwarfs stretch the definition even further. Extra large planets can be considered failed stars so your example could also represent a trinary system.

ARGGHHHH. longest X-post ever.

	30-07-2005 16:49									#27
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A rose planet by any other name....

	30-07-2005 23:57									#28
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Calling objects pluto size or larger planets is fine by me. Calling anything smaller a planetoid is fine also.

In order for us to call something a planet. Criteria should be,

It has to revolve around the sun
It has to have a diameter of 1000km or more

There. I think I settled it. Lets start burning our space history books now and make new ones

	31-07-2005 07:27									#29
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quote: Originally posted by faded glory It has to revolve around the sun It has to have a diameter of 1000km or more

1. Why 1000km?
2. We've discovered lots of extrasolar planets and none of them revolve around the sun.

	31-07-2005 08:48									#30
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can we name this one planet X?