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Thread: Neptune to Pluto distance

  1. #1
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    If I were an observer on Neptune, I could see Sol as a rather bright star Surely Triton would be clearly visible, and there are a few rocky moonlets, Nereid et al

    Then there is Pluto, this fascinating object of nature that we argue is a KBO, a planet or both.

    An astrologer told me once that Pluto and Neptune were never far apart in Earth's sky. This is never more than sixty degrees from our POV, with confusing if unbelievable effects upon the human race, but that is another story. Apparently this is because their orbital periods are in a 3 to 2 lock

    Now my question is this. To a Neptunian (who we assume to be heliocentrically ignorant) would Pluto appear to be an object that goes around the world as Luna goes round Terra?, and as Sol goes around Neptune?

    If that is so, to a Neptunian little blue man, is Pluto just another moon like Triton?which, I understand would appear to go the other way round.


    What is the largest physical separation of the two objects? Is Pluto ever on the other side of Sol?

    Is Pluto then a trinity, planet, moon and KBO?

    Zwi

  2. #2
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    On 2003-03-08 14:33, zwi wrote:
    If I were an observer on Neptune, I could see Sol as a rather bright star Surely Triton would be clearly visible, and there are a few rocky moonlets, Nereid et al

    Then there is Pluto, this fascinating object of nature that we argue is a KBO, a planet or both.

    An astrologer told me once that Pluto and Neptune were never far apart in Earth's sky. This is never more than sixty degrees from our POV, with confusing if unbelievable effects upon the human race, but that is another story. Apparently this is because their orbital periods are in a 3 to 2 lock
    Your astrologer friend is full of [something]. The only thing correct in that is that the orbits (around the Sun) are in 3:2 resonance.
    Now my question is this. To a Neptunian (who we assume to be heliocentrically ignorant) would Pluto appear to be an object that goes around the world as Luna goes round Terra?, and as Sol goes around Neptune?
    No! Both orbit the Sun.
    If that is so, to a Neptunian little blue man, is Pluto just another moon like Triton?which, I understand would appear to go the other way round.
    Again, no.

    What is the largest physical separation of the two objects?
    Approximately 78 AU (11.68 billion kilometers)

    Is Pluto ever on the other side of Sol?
    Yes, but it hasn't happened since either was discovered.
    Is Pluto then a trinity, planet, moon and KBO?
    No!


    _________________
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    <font size=-1>[ This Message was edited by: Kaptain K on 2003-03-08 15:08 ]</font>

  3. #3
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    Dear Kaptain

    Many thanks for your answers.

    I drew a lot of views for my questions but yours was the only reply, thanx again

    Perhaps I asked too many questions, because now I am even more mystified

    Let me ask just one now

    Why are the orbits of Neptune and Pluto around the Sun in 3:2 resonance?

    Zwi

  4. #4
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    Periodic Orbits in the 3:2 Orbital Resonance and Their Stability
    Authors: Varadi, F.
    Affiliation: AA(Institute of Geophysics and Planetary Physics, UCLA, 405 Hilgard Avenue, Los Angeles, CA 90095-1567)
    Journal: The Astronomical Journal, Volume 118, Issue 5, pp. 2526-2531.
    Publication Date: 11/1999
    Abstract

    Periodic orbits in the external 3:2 orbital resonance are investigated in the context of the planar, elliptic restricted three-body problem. Differential continuation is employed to determine the location of
    such orbits. Their stability and periods of libration around them are also computed. Stable, nearly circular orbits for hypothetical small bodies are found in extrasolar planetary systems having a giant planet
    on a very eccentric orbit. These orbits cross the orbit of the giant planet, but the 3:2 orbital resonance keeps them safely apart in a configuration analogous to that of Neptune and Pluto.
    In effect, the answer is because that's what is stable. Another orbit would be dynamically unstable and therefore wouldn't stick around for us to observe.

    Here's a general hint: most astrologers don't know enough about astronomy (otherwise they wouldn't be astrologers).

    <font size=-1>[ This Message was edited by: JS Princeton on 2003-03-09 14:44 ]</font>

  5. #5
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    Quote from intro of "21st Century Astronomy"

    Student: "Professor, what's the difference between Astrology and Astronomy?"

    Professor: "Math. Lots and lots of math."

    No more students!

  6. #6
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    Thank you for your reply, JS Princeton. Believe it or not, I did understand a bit of it. I am now asking you or anyone to amplify it

    I am not talking about astrology. It's a complete red herring that I shouldn't have introduced. I apologize for that. I wont mention astrology ever again. Promise

    1. What is the theoretical minimal separation of Pluto and Neptune? Since Pluto starts off outside Neptune's orbit and then goes inside it is it possible for the two planets to collide? Since Pluto is at one time North of Neptune and at others South, can I imagine the planets' paths may intersect? Or is there something about the orbital mechanics that prohibits this?

    2 Or is there something about the orbital mechanics that means that both planets can not at aphelion at the same time? If so what is the theoretical maximum separation?

    3 My hypothetical little blue man is a Babylonian astromonomer, who I imagine observing the skies from Neptune, granted clear skies and great seeing and vision.(And lots and lots of math!) To him, the fixed stars appear to rotate around the world with every rotation of Neptune on its axis. Triton may be the lesser light to rule the night, with its retrograde motion. Other lights would wander about the heavens like planets, which they are

    Our astronomer could make out Earth/Luna as a pair, and the Galilean satellites would do their dance around Jupiter. From these observations he might infer that the bright star Sol is what erything rotates about

    But what would the apparent path of Pluto be?

    4 If Pluto's path is gravitationally tied up with the much bigger Neptune, could he not infer that Pluto is a moon?

    Please take my questions seriously I am not an astronomer but have some math

    If anyone wants to know this scenario was developed in a story I read many years ago In Astounding Science Fiction

    Zwi






    <font size=-1>[ This Message was edited by: zwi on 2003-03-09 18:51 ]</font>

  7. #7
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    Pluto's orbit is more elliptical than Neptune (I think), and also inclined.
    Together, these attributes allow its orbit to fit around or inside Neptune's orbit (I'm not sure which!).

  8. #8
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    [quote]4 If Pluto's path is gravitationally tied up with the much bigger Neptune, could he not infer that Pluto is a moon? /[quote]
    They aren't tied to each other at all.
    But what would the apparent path of Pluto be?
    It would be very similar to the apparant path of Mars to Earth - just more eccentric. It covers the whole sky but every now and then moves with retrograde motion (lots of retrograde motion).

    I'm not sure what you are looking for here. There really isn't anything terribly unique about the relationship between those two planets.

  9. #9
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    On 2003-03-09 18:43, zwi wrote:
    1. What is the theoretical minimal separation of Pluto and Neptune? Since Pluto starts off outside Neptune's orbit and then goes inside it is it possible for the two planets to collide? Since Pluto is at one time North of Neptune and at others South, can I imagine the planets' paths may intersect? Or is there something about the orbital mechanics that prohibits this?
    The minimum distance between Neptune and Pluto is 18 AU. Relative minima occur at three points in Pluto's orbit: when Pluto is at aphelion and Neptune is in conjunction (usually the absolute minimum), and when Pluto is near perihelion.

    Also, the tilt of Pluto's orbit is such that it is farthest away from the plane of Neptune's orbit when Pluto is at perihelion and aphelion.
    2 Or is there something about the orbital mechanics that means that both planets can not at aphelion at the same time? If so what is the theoretical maximum separation?
    Neptune's orbit is very nearly circular, so aphelion for Neptune doesn't really matter here. Neptune is either in conjunction or opposition with Pluto at Pluto's aphelion passages, and it alternates, so I believe the maximum distance between them should be 50 + 30 = 80 AU.

    I will have to think some about question 3.
    4 If Pluto's path is gravitationally tied up with the much bigger Neptune, could he not infer that Pluto is a moon?
    No, for an object to be a moon it would have to be close to its primary, and as has been demonstrated Pluto is actually always quite far away from Neptune. There are other objects that are also in resonance with other bodies, for example the Trojan asteroids of Jupiter, which are in 1:1 resonance and follow or lead Jupiter by approximately 60 degrees. No satellites of satellites are known yet, but there are co-orbiting satellites in the Saturnian system (and I think now in the Neptunian system as well).

  10. #10
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    Many thanks to Celestial Mechanic for his answers

    I was able to find an article in Scientific American of Sept 1999 by Renu Malhotra

    http://www.sciam.com/article.cfm?art...mber=1&catID=2

    about planetary migration in which the writrer suggested that thee orbits of our gas giants have evolved because of interactions with planetisimals Jupiter's has shrunk a little, the others' have dilated. Pluto as a result has moved up and obliquely It is in a 3 to 2 relationship with Neptune. Its orbit is stable, although most Neptune crossing orbits are unstable

    Furthermore many of the KBOs have evolved into a 3 to 2, 4 to 3 even 5 to 3 relation with Neptune

    I know this is one writer only. I found it very interesting and wonder whether others agree or whether more recent work has or has not confirmed Any one know?

    Thanks again Celestial Mechanic I notice you live in Milwaukee Wis I used to live there in the Lombardi glory years and the beginning of the less glorious Brewers

    Kind regards

    Zwi

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