Page 1 of 2 12 LastLast
Results 1 to 30 of 50

Thread: Kuiper Belt Orphan?

  1. #1
    Join Date
    Jan 2003
    Posts
    229
    This is a discussion sprung from Colt's poll thread Pluto: Planet or KBO?.

    I suggest, if you haven't, to post your vote in that thread first.


    From that thread...
    On 2003-02-25 16:15, Zap wrote:
    KBO all the way. Still hard with tradition and all, but I mean come on it's among so many other bodies of its kind. If another KBO as large or larger than Pluto is discovered, I think that would answer the debate itself.
    I don't get your reasoning there. Are you saying that it stays classified as a planet as long as KBO's are smaller than Pluto?

    <font size=-1>[ This Message was edited by: DaveOlden on 2003-02-26 03:25 ]</font>

  2. #2
    Join Date
    Feb 2003
    Posts
    58
    I can see the logic in that. Know one has to say they were wrong in saying or maintaining it is a planet as long as it is the largest KBO around. Still it is a KBO.

  3. #3
    Join Date
    Jan 2003
    Posts
    229
    Not sure I understand your clarification there. (Or perhaps I didn't phrase my initial challenge clearly).

    A KBO is, as I am learning, classified not as much by size as by what makes it up.

    There has been debate over whether size even defines "planet".

    A definition of Planet from dictionary.com:
    plan-et. n.

    1. A nonluminous celestial body larger than an asteroid or comet, illuminated by light from a star, such as the sun, around which it revolves. In the solar system there are nine known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.


    2. One of the seven celestial bodies, Mercury, Venus, the moon, the sun, Mars, Jupiter, and Saturn, visible to the naked eye and thought by ancient astronomers to revolve in the heavens about a fixed Earth and among fixed stars.


    3. One of the seven revolving astrological celestial bodies that in conjunction with the stars are believed to influence human affairs and personalities.
    The second two, if we go with those, throw out Neptune, too! You think classifying Pluto is controvertial!! Trying fitting an orphaned Neptune into KBO class.

    I don't think size should be the only measure.What;s stopping Pluto from being the largest known Kuiper Object as is?

    Good ol' Yoda, "Size matters not, judge me by my size do you?"


    <font size=-1>[ This Message was edited by: DaveOlden on 2003-02-26 03:23 ]</font>

  4. #4
    Join Date
    Feb 2003
    Posts
    2,689
    On 2003-02-26 02:47, DaveOlden wrote:
    I don't get your reasoning there. Are you saying that it stays classified as a planet as long as KBO's are smaller than Pluto?
    Well, Zap thinks it's a KBO anyway, so that's not quite right.

    The argument against changing its classification would be surely muted if a lot of larger-than-Pluto KBOs were discovered, don't you think? Even if one were discovered that was about the same size.

    One of the problems there is the idea of "size." I'm reading Timothy Ferris's book and he mentions that Quaoar is about half of Pluto's size. He's talking about radius--but everybody knows that if a sphere is half the radius of another, it's actually an eighth of the volume. Clearly, volume is the most appropriate measure. Or is it?

  5. #5
    Join Date
    Feb 2002
    Posts
    4,070
    Well, if you live on a planet, than maybe surface area is what counts...

    If you use enough dimensions, you can make the difference between two bodies as large as you want... [img]/phpBB/images/smiles/icon_wink.gif[/img]

    The problem here is, that we have a mixture of history, nomenclature and opinions. If Pluto would be discovered today, we may call it a pretty big KBO. Formally I'd call it a KBO, but I've no problem with keeping Pluto a planet. We know since a long time that the mare on the Moon are no oceans, but we still call them mare. It preserves history. If Pluto would from now on be just a KBO, the exciting history of its discovery would be forgotten.

    Harald

    <font size=-1>[ This Message was edited by: kucharek on 2003-02-26 07:00 ]</font>

  6. #6
    Join Date
    Jan 2003
    Posts
    229
    Perhaps a compromise...

    Pluto: a Kuiper Belt Origin Planet, or K-BOP.

    [img]/phpBB/images/smiles/icon_biggrin.gif[/img]


  7. #7
    Join Date
    Feb 2003
    Posts
    2,689
    Are you talking about a Klingon Bird of Prey, or a radio station in Pleasanton, TX, USA?

  8. #8
    Join Date
    Jan 2003
    Posts
    229
    On 2003-02-26 07:15, kilopi wrote:
    Are you talking about a Klingon Bird of Prey, or a radio station in Pleasanton, TX, USA?
    As long as the Klingon Bird of Prey doesn't fire at it, and the radio station is respectful when they talk about it, I'm fine with both. Station can pay for advertising to fund study, too. [img]/phpBB/images/smiles/icon_wink.gif[/img]

  9. #9
    Join Date
    Feb 2003
    Posts
    2,689
    On 2003-02-26 06:59, kucharek wrote:
    Well, if you live on a planet, than maybe surface area is what counts...
    But nobody lives on Pluto or Quaoar. At least, no one I know personally.

    In the solar system, mass is what is important--and that's highly correlated with voume, not surface area, nor radius.

  10. #10
    Join Date
    Jan 2003
    Posts
    229
    Well! What a timely article... today at Space.com (just got the newsletter in my email)


    Probe to Pluto...!
    Here's a quote from the article
    The probe is scheduled for launch in 2006 and would arrive at Pluto in about 2015, study the tiny planet and its moon, Charon, and then continue on in search of Kuiper Belt Objects (KBOs). These frozen rocks, some roughly half the size of Pluto, have only been known since the early 1990s. Some scientists argue that Pluto is actually not a planet, but a KBO instead.
    The article is here.

  11. #11
    Join Date
    Jan 1970
    Posts
    128
    DaveOlden.


    “Perhaps a compromise...

    Pluto: a Kuiper Belt Origin Planet, or K-BOP.”


    This very question has been vexing me for some time now. The “birthplace” of comets is considered to be the Jupiter-Saturn region, which were then expelled to the outskirts of the system during the “mop-up”. (late stage accretion)


    The “birthplace” of the KBOs is considered to be the Uranus-Neptune region, which were then tossed out to their current position. So, which is more likely? Was Pluto’s point of origin in the Uranus-Neptune region and simply failed to “park” itself in the Kuiper belt or did Pluto achieve a stable orbit “out there” only to be kicked back in-system?

  12. #12
    Join Date
    Feb 2003
    Posts
    58
    [quote]
    On 2003-02-26 03:16, DaveOlden wrote:
    Not sure I understand your clarification there. (Or perhaps I didn't phrase my initial challenge clearly).

    A KBO is, as I am learning, classified not as much by size as by what makes it up.

    There has been debate over whether size even defines "planet".

    A definition of Planet from dictionary.com:
    plan-et. n.

    1. A nonluminous celestial body larger than an asteroid or comet, illuminated by light from a star, such as the sun, around which it revolves. In the solar system there are nine known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
    It may not say size in the definition but someone in the pas has decided that size does govern classification. If this were not true we would have a nice little belt of planets in our galaxy. [img]/phpBB/images/smiles/icon_smile.gif[/img]

  13. #13
    Join Date
    Jan 2003
    Posts
    229
    Good point canadianfury. [img]/phpBB/images/smiles/icon_smile.gif[/img]

    Maybe size is less of an issue, and more of a given.
    Composition I think is a major factor.

  14. #14
    Join Date
    Feb 2003
    Posts
    2,689
    On 2003-02-26 11:43, canadianfury wrote:
    It may not say size in the definition but someone in the pas has decided that size does govern classification.
    That definition may not say "size" but it says "larger"--which is a reference to size. One of those other threads discusses what size means--is it radius, surface area, volume, or mass? Pluto may only be twice the radius of Quaoar, but it is that cubed in volume or mass.

  15. #15
    Join Date
    May 2002
    Posts
    2,045
    I find it interesting that "everyone" is regarding size as a means to determine what a planet is.

    What sells me most to Pluto as a KBO is the eccentricity of its orbit. Mercury through Neptune are on a similar plane of ecleptic, but Pluto is on an entirely different one. To me, I would regard the planets of a sun to be on the same ecleptic.


  16. #16
    Join Date
    Nov 2001
    Posts
    1,947
    Size, eccentricity, and the fact that everyone's starting to get convinced that Pluto is part of a group of similar bodies.

    Origin has also been suggested as a criterion, but the problem with that is that it's difficult to be certain of how a stellar body originated.

    If we travelled to another solar system with planet-like objects, would we wait until we had studied their formation, to decide whether they were planets or something else?

  17. #17
    Join Date
    Dec 2002
    Posts
    2,171
    On 2003-02-26 17:05, informant wrote:
    Size, eccentricity, and the fact that everyone's starting to get convinced that Pluto is part of a group of similar bodies.
    And that's part of the deal. If we were to classify Pluto as a KBO, then we're saying that:
    • Pluto is larger that any other known KBO
    • Pluto's orbit is closer to the sun than any other known KBO
    • Pluto's orbit is less eccentric than that of any other known KBO
    • Pluto is the only KBO known to have a moon
    It's precisely because of all of these superlatives that Pluto is still thought of as a planet.

  18. #18
    Join Date
    May 2002
    Posts
    561
    On 2003-02-26 16:35, nebularain wrote:
    ...To me, I would regard the planets of a sun to be on the same ecleptic...
    Two questions:

    1. I believe ecliptic is defined as the plane of the Earth's orbit around the sun. How do you choose the "ecliptic" of a foreign star system, assuming they don't have another Earth over there?

    2. If a massive body flies through our system and perturbs one of the planets off of the ecliptic without ejecting it from the system, then is it still a planet?

  19. #19
    Join Date
    Feb 2003
    Posts
    2,689
    On 2003-02-26 16:35, nebularain wrote:
    I find it interesting that "everyone" is regarding size as a means to determine what a planet is.
    But that is the criteria that we use to differentiate between meteoroids and asteroids. Why not planetoids and planets too? I admit that the criteria is not well established.
    On 2003-02-26 18:03, traztx wrote:
    1. I believe ecliptic is defined as the plane of the Earth's orbit around the sun. How do you choose the "ecliptic" of a foreign star system, assuming they don't have another Earth over there?
    Pretty much line it up with the plane of the central star's rotation, probably?

  20. #20
    Join Date
    Feb 2003
    Posts
    58
    Size is a relative term so it could be mass, volume, radius, etc. I think, in terms of Pluto, size is the proper word as it covers all these terms.

  21. #21
    Join Date
    Feb 2003
    Posts
    2,689
    On 2003-02-26 22:22, canadianfury wrote:
    Size is a relative term so it could be mass, volume, radius, etc. I think, in terms of Pluto, size is the proper word as it covers all these terms.
    But, depending upon which one you choose, the results might be different. For instance, A may be twice the radius of B, but it'll be 8 times the volume. C could have smaller volume than B, but have more mass.

  22. #22
    Join Date
    Oct 2001
    Posts
    321
    On 2003-02-26 17:37, tracer wrote:
    And that's part of the deal. If we were to classify Pluto as a KBO, then we're saying that:
    • Pluto is larger that any other known KBO
    • Pluto's orbit is closer to the sun than any other known KBO
    • Pluto's orbit is less eccentric than that of any other known KBO
    • Pluto is the only KBO known to have a moon
    It's precisely because of all of these superlatives that Pluto is still thought of as a planet.
    Are you sure? I seem to recall that they have now discovered a couple of KBO's that have moons. Here's one paper that discusses it, listed on the Lowell Observatory web site:

    Noll, K., Stephens, D., Grundy, W., Buie, M., Millis, R., Spencer, J., Tegler, S., and Romanishin, W. , Detection of Two Binary Trans-Neptunian Objects, 1997 CQ29 and 2000 CF105, with Hubble Space Telescope. In preparation, to be submitted to the Astronomical Journal.

    Also, are you sure that all the other hundreds of KBO's have more eccentric orbits than Pluto? That seems unlikely...

  23. #23
    Join Date
    Jun 2002
    Posts
    4,813
    On 2003-02-26 18:03, traztx wrote:
    1. I believe ecliptic is defined as the plane of the Earth's orbit around the sun. How do you choose the "ecliptic" of a foreign star system, assuming they don't have another Earth over there?
    A more appropriate plane is the invariable plane (sometimes called the Laplacian plane after Laplace who suggested using it), which is the plane perpendicular to the total angular momentum of the Solar System. (Of course a similar definition applies to other solar systems.)

    The orbital motion of Jupiter makes the biggest contribution to the total angular momentum vector, so it's no surprise that the invariable plane is almost the plane of Jupiter's orbit. The Earth's orbit is inclined at about 1.6 degrees to this invariable plane and precesses in a retrograde sense with a period of something like 130,000 to 140,000 years.

  24. #24
    Join Date
    Feb 2003
    Posts
    58
    On 2003-02-27 01:16, kilopi wrote:
    On 2003-02-26 22:22, canadianfury wrote:
    Size is a relative term so it could be mass, volume, radius, etc. I think, in terms of Pluto, size is the proper word as it covers all these terms.
    But, depending upon which one you choose, the results might be different. For instance, A may be twice the radius of B, but it'll be 8 times the volume. C could have smaller volume than B, but have more mass.
    That is exactly right. If any of the charcteristics you listed were in conflict, we most definitely could not maintain it is a planet.

  25. #25
    Join Date
    Feb 2003
    Posts
    2,689
    On 2003-02-28 10:39, canadianfury wrote:
    That is exactly right. If any of the charcteristics you listed were in conflict, we most definitely could not maintain it is a planet.
    But that's why I disagree. Imagine an object that was a low density balloon made of mylar or something, like the early comm satellite Echo, but with a radius larger than Pluto's. I don't think anyone would call that a planet, and it would be in conflict with one of the size characteristics--but it's existence wouldn't argue against planethood for Pluto.

  26. #26
    Join Date
    Oct 2001
    Posts
    321
    When Ceres was first discovered, it was considered to be a planet. It was only after other asteroids started showing up, and also when the first size estimates of Ceres were made, that it was decided that it wasn't really a "planet".

    It just so happened that the first asteroid discovered turned out to be the largest one in the asteroid belt.

    It could very well be that Pluto will turn out to be the largest transNeptunian object. But even so, if Ceres is not a planet, then I don't see why Pluto should be.


  27. #27
    Join Date
    Nov 2001
    Posts
    1,947
    Do you think people would accept the term "planetoid" for Pluto?

  28. #28
    Join Date
    Feb 2003
    Posts
    2,689
    On 2003-02-28 12:13, aurorae wrote:
    It just so happened that the first asteroid discovered turned out to be the largest one in the asteroid belt.
    Yeah, the largest is easier to find.
    It could very well be that Pluto will turn out to be the largest transNeptunian object. But even so, if Ceres is not a planet, then I don't see why Pluto should be.
    Some people feel that it shouldn't be just because it is smaller. It also doesn't appear to be very round.
    On 2003-02-28 12:34, informant wrote:
    Do you think people would accept the term "planetoid" for Pluto?
    No, it already means "asteroid".

  29. #29
    Join Date
    May 2002
    Posts
    2,045
    What about the term "planetesimal?"


  30. #30
    Join Date
    Feb 2003
    Posts
    58
    On 2003-02-28 11:03, kilopi wrote:
    On 2003-02-28 10:39, canadianfury wrote:
    That is exactly right. If any of the charcteristics you listed were in conflict, we most definitely could not maintain it is a planet.
    But that's why I disagree. Imagine an object that was a low density balloon made of mylar or something, like the early comm satellite Echo, but with a radius larger than Pluto's. I don't think anyone would call that a planet, and it would be in conflict with one of the size characteristics--but it's existence wouldn't argue against planethood for Pluto.
    I am having trouble picturing anything man-made with a radius similar to Pluto. If you could give me an example of something in nature with a conflict of charcteristics I think we could debate the point. The problem is anything in nature that brings up the debate of "size" could probably bring up the debate of planet.

Similar Threads

  1. Where Are All the Kuiper Belt Objects?
    By Fraser in forum Universe Today
    Replies: 0
    Last Post: 2008-Oct-03, 04:00 PM
  2. Mass of the Kuiper Belt
    By dtilque in forum Space/Astronomy Questions and Answers
    Replies: 7
    Last Post: 2007-Jul-14, 08:43 AM
  3. Replies: 32
    Last Post: 2006-Jan-01, 06:18 AM
  4. Kuiper belt
    By Jakenorrish in forum Astronomy
    Replies: 16
    Last Post: 2005-Sep-20, 05:28 AM
  5. Fomalhaut's Kuiper Belt
    By Kullat Nunu in forum Astronomy
    Replies: 7
    Last Post: 2005-Jun-23, 06:36 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •