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B Why do we suspect planet 9

  1. Mar 24, 2016 #1


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    Why do we suspect a planet 9 and what are the implications if there is a planet 9?

    arXiv:1603.07247 [pdf, other]
    Is there an exoplanet in the Solar System?
    Alexander J. Mustill, Sean N. Raymond, Melvyn B. Davies
    Comments: 5 pages + appendix. Submitted to MNRAS Letters
    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    We investigate the prospects for the capture of the proposed Planet 9 from other stars in the Sun's birth cluster. Any capture scenario must satisfy three conditions: the encounter must be more distant than ~150 au to avoid perturbing the Kuiper belt; the other star must have a wide-orbit planet (a>~100au); the planet must be captured onto an appropriate orbit to sculpt the orbital distribution of wide-orbit Solar System bodies. Here we use N-body simulations to show that these criteria may be simultaneously satisfied. In a few percent of slow close encounters in a cluster, bodies are captured onto heliocentric, Planet 9-like orbits. During the ~100 Myr cluster phase, many stars are likely to host planets on highly-eccentric orbits with apastron distances beyond 100 au if Neptune-sized planets are common and susceptible to planet--planet scattering. While the existence of Planet 9 remains unproven, we consider capture from one of the Sun's young brethren a plausible route to explain such an object's orbit. Capture appears to predict a large population of Trans-Neptunian Objects (TNOs) whose orbits are aligned with the captured planet, and we propose that different formation mechanisms will be distinguishable based on their imprint on the distribution of TNOs.
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  3. Mar 24, 2016 #2
    Planet 9 is known to be a dwarf planet, it is the largest known planet in the kuiper belt. When discovered in 1930, it was considered the 9th planet, this change in 2006 with the adoption of a formal definition of planet . Well the region beyond Neptune is still greatly unexplored, because it appears to consists mainly of rock and ice, this implies that the implications of the 9th planet are not yet found till the region beyond Neptune is thoroughly explored
  4. Mar 24, 2016 #3
    Thanks for the link :smile:, You have no idea how handy that is going to be for me. I'm currently in a discussion on another site about this very subject.
  5. Apr 6, 2016 #4


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  6. Apr 6, 2016 #5
    Dear Kyx.

    Another mystery is Piet Hut and Rich Muller's Nemesis, a supposed companion of our sun, never seen but that could originate periodic mass extintions in Earth every 26 million years. Could it be a black hole? It doesn't seem probable, but always are those who love amazing hypothesis, isn't that so?
  7. Apr 6, 2016 #6

    Vanadium 50

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    The evidence for a black hole is on par with evidence that it's the actual Greek goddess Nemesis.
  8. Apr 6, 2016 #7
    The motions of easily observable objects in the solar system don't add up to a perfect complete model for the solar system.
    There definitely is stuff out there which is not accounted for as yet.
    There are many possibilities, but the one I like the most is that there could be a number of large objects, (but not black hole large), in the Oort cloud.
  9. Apr 8, 2016 #8
    Pluto was demoted so that astronomers could talk about the existence of "planet 9" at the same time as ridiculing those talking about the existence of planet X.
  10. Apr 8, 2016 #9
    No, Pluto was reclassified as a dwarf planet because we now know there are many other similar bodies beyond Neptune in approximately similar orbits, so if Pluto remained as a planet then all those objects would have to be defined as planets too.
    The largest asteroid, Ceres, was upgraded to 'minor planet' status at the same time.
  11. Apr 10, 2016 #10

    jim mcnamara

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    Well, some astrophysicists in Bern think a model of planet 9 would be useful in developing a search. And to explain why it is likely that we have not yet used tools that would be likely to succeed. If you remember, this is kind of like the story of the discovery of Neptune.
    from https://en.wikipedia.org/wiki/Discovery_of_Neptune :
    E. Linder/C. Mordasini: «Evolution and Magnitudes of Candidate Planet Nine» http://www.aanda.org/10.1051/0004-6361/201628350
    http://www.unibe.ch/news/media_news/media_relations_e/media_releases/2016_e/media_releases_2016/planet_9_takes_shape/index_eng.html [Broken]

    Someone who is competent in the field (not me) could comment. @Chronos
    Last edited by a moderator: May 7, 2017
  12. Apr 10, 2016 #11
    It's certainly interesting to think there is a full-fledged planet - not an asteroid, dwarf or minor planet - yet to be discovered. It would be a tremendous discovery and I am happy to know someone is looking into it. However, it's hypothetical at this point, as there is not enough evidence for it to be theory.
  13. Apr 11, 2016 #12


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    And Pluto is not the first body to be reclassified "downwards". At one point, It, along with Pallas, Juno and Vesta were all listed as planets and were later demoted.
    "Minor planet" was the term in use before 2006 and Ceres was considered one, as were the other asteroids. After 2006 it was reclassified to 'Dwarf planet' along with Eris (which was, for a short time considered a possible 10th planet). Later, Hamea and Makemake were added to the role of Dwarf planets, bringing the list up to 5.
  14. Apr 11, 2016 #13
    The WISE survey has put upper limits on those objects however: There are no Neptune-sized objects closer than 700 AU, and no Jupiter sized objects out to a light year (63,000 AU.)
  15. Apr 16, 2016 #14
    I'm sure I remember Stephen Hawking saying in 'A Brief History of Time' that it is possible that a black hole exists beyond the orbit of Pluto. I would like that to be the case :smile:
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