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Thread: The Football Planet

  1. #31
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    And... ANOTHER football-shaped planet! WASP-121b is in for the score! Except this football is a gas giant, not a terrestrial world.

    https://phys.org/news/2019-08-distan...as-planet.html

    The official paper (just the abstract):

    https://iopscience.iop.org/article/1...38-3881/ab2986
    Do good work. —Virgil Ivan "Gus" Grissom

  2. #32
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    The original paper on the iron football planet has been revised, 13 months after its release. Same https as before, a bit longer now.
    Do good work. —Virgil Ivan "Gus" Grissom

  3. #33
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    Footballs are not shaped like that. Rugby balls are.

  4. #34
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    The planet Jinx in Larry Niven's Known Space series was the first example of this in fiction (so far as I am aware).

  5. #35
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    Nice article with rotating Haumea gif, must see for weirdness.

    https://earthsky.org/space/100-new-m...beyond-neptune

    Last edited by Roger E. Moore; 2020-Mar-30 at 01:52 PM.
    Do good work. —Virgil Ivan "Gus" Grissom

  6. #36
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    Do good work. —Virgil Ivan "Gus" Grissom

  7. #37
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    I made this model, which I'll import into Celestia in due course.
    I'm not too clear on how big to make it though. The article says it has 0.6 x Earth's radius - is that an average, or do I pick one of its axes?
    Attached Images Attached Images

  8. #38
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    Quote Originally Posted by eburacum45 View Post
    I'm not too clear on how big to make it though. The article says it has 0.6 x Earth's radius - is that an average, or do I pick one of its axes?
    Read the original article, at top of this thread. It had the details, long axis vs short axes. LATE EDIT: I was wrong, it didn't.
    Last edited by Roger E. Moore; 2020-Apr-08 at 06:38 PM.
    Do good work. —Virgil Ivan "Gus" Grissom

  9. #39
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    That is an amazing model!
    Do good work. —Virgil Ivan "Gus" Grissom

  10. #40
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    Quote Originally Posted by Roger E. Moore View Post
    Read the original article, at top of this thread. It had the details, long axis vs short axes.
    "As it orbits less than one stellar radius from the host star’s photosphere (a/R⋆ = 1.9), KOI 1843.03 will be significantly elongated in the direction of the star due to tidal distortion. Based on the parameters of KOI 1843.03, our models predict that it must be at least 31% longer along the star-planet line than along the perpendicular axes (aspect ratio of about 1.3), and our models support a value up to nearly twice as long along the starplanet line (aspect ratio of almost 1.8); various possibilities are illustrated in Figure 5. For comparison, Saturn has an aspect ratio of about 1.1."

    Well, I thought it had the dimensions. I believe the radius is an average. Someone else might be able to step in here and help.... ???
    Do good work. —Virgil Ivan "Gus" Grissom

  11. #41
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    I assumed that this prolate spheroid has the same volume as a sphere with 0.6 x the Earth's radius; this gives me a major radius of 4625km. I will use this as the radius of my Celestia model unless someone comes up with a more accurate figure.

  12. #42
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    Have only a vague idea of what this is about, but it clearly relates to "football" planets like Haumea & the like (and more spherical worlds like Mars, and likely even the Earth). Good luck with it.

    https://arxiv.org/abs/2004.08218
    Inertial modes of a freely rotating ellipsoidal planet and their relation to nutations
    Jeremy Rekier, Santiago A. Triana, Antony Trinh, Veronique Dehant
    Submitted on 17 Apr 2020
    We compute the inertial modes of a freely rotating two-layer planetary model with an ellipsoidal inviscid fluid core and a perfectly rigid mantle. We derive analytical formulae for the frequencies of the Free Core Nutation (FCN) and Chandler Wobble (CW) which are valid to all orders in the core and mantle ellipticity, and we show how the FCN and CW are the direct generalisation of the purely fluid Spin-Over mode (SO) and of the Eulerian Wobble (EW) to the case where the mantle can oscillate freely around a state of steady rotation. Through a numerical computation for an axisymmetric (oblate spheroidal) planet, we demonstrate that all other inertial modes of the steadily rotating fluid core are also free modes of the freely rotating two-layer planet.

    https://en.wikipedia.org/wiki/Chandler_wobble

    https://en.wikipedia.org/wiki/Nutation
    Last edited by Roger E. Moore; 2020-Apr-20 at 02:43 AM.
    Do good work. —Virgil Ivan "Gus" Grissom

  13. #43
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    Hot Jupiters can develop a pronounced football shape as well. This article on Hot Jupiters describes their shapes.

    https://phys.org/news/2020-04-hot-ju...chemistry.html
    Do good work. —Virgil Ivan "Gus" Grissom

  14. #44
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    Quote Originally Posted by Roger E. Moore View Post
    Hot Jupiters can develop a pronounced football shape as well. This article on Hot Jupiters describes their shapes.

    https://phys.org/news/2020-04-hot-ju...chemistry.html
    The article describes the shape as an egg. The small end is toward the star, and becomes more and more pointed as a hypothetical body gets closer to the Roche limit. Perhaps this thread should be retitled "The Egg Planet".

  15. #45
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    Quote Originally Posted by Hornblower View Post
    The article describes the shape as an egg. The small end is toward the star, and becomes more and more pointed as a hypothetical body gets closer to the Roche limit. Perhaps this thread should be retitled "The Egg Planet".
    Could the article be wrong? Other papers cited here show a definite oval shape, the antisolar end of the planet like the solar end. No one has said "egg-like" before when describing gravitationally distorted planets.
    Do good work. —Virgil Ivan "Gus" Grissom

  16. #46
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    If I am not mistaken, the shape does indeed get closer to an ellipsoid at larger distances, so a rugby-type football will do after all.

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