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Thread: Exoplanet formation mystery

  1. #1 Exoplanet formation mystery 
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    Hi everyone, I was reading about a new exoplanet (TrES-4) that's been discovered by the Transatlantic Exoplanet Survey, http://www.unregisterednews.com/content/view/198/51.

    Does anyone have any idea about how such a huge planet could form so close to a star? It only takes 3.5 days to orbit! What kind of a star is GSC02620-00648, might the type of star have a part to play?


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  3. #2  
    Forum Ph.D. Wolf's Avatar
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    That's the current question. No one knows. It breaks current understandings of gaseous bodies in solar models.

    Not to sound pesemistic, but there's a few top-notch scientists working on this right now, so I doubt anyone posting on this forum has the answer. Don't take that as an insult, please.

    However, I will point out that this is one of those things where we find something that we didn't know of, and didn't know could happen, and don't understand. According to some, such things as this don't exist, since we have "a complete understanding of physics." Oh well.

    It would be curious to figure out what's going on. There is speculation that there must be some kind of mass loss between the planet and the star (ie - the star's accumulating matter from the close planet). If that's the case, the planet will be destroyed soon. That has another implication in that it could indicate that the planet wasn't originally from that position in its solar system. It could have had an orbit that was slowly degrading over time, and we've just taken a snapshot of it in its final stages of "life."

    If that's the case, then there's no mystery at all.


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    Forum Senior miomaz's Avatar
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    Sounds interresting, but the link is broken... to bad.

    Does some one know If we made a picture of a planet actually soaring into a star, I mean that would really be a fun thing to look at.
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  5. #4  
    Forum Ph.D. Wolf's Avatar
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    There's probably some out there. There's quite a bit of artistic renderings, since most deep-space telescope images aren't in the PR-spectrum.

    What it would be like all depends on how the star interacted with the planet. If the planet slowly lost orbit, or drifted past the star, the event would be a slow death by gradual consumption and vaporization. If the planet impacted the star, it would all depend on the mass of the planet. For instance, the Earth hitting the Sun probably wouldn't be much to look at. Jupiter would probably make a pretty fireball as the Sun torched it before it actually made contact. If there was a planet of rock the size of Jupiter, it might be more exciting.
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  6. #5 Re: Exoplanet formation mystery 
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    Quote Originally Posted by darudethedj
    Does anyone have any idea about how such a huge planet could form so close to a star?
    It absolutely did not form close to the star. We are accustomed to thinking of the planets as being in stable orbits. During the process of planetary assembly from protoplanets and the sweeping up of gas bodies are flying everywhere. Some migrate inwards, some outwards. Some may be ejected from the system entirely. Only later to things settle down to relative stability.

    Here is a fairly old set of comments on the matter.
    Weidenschilling et al, "Gravitational scattering as a possible origin for giant planets at small stellar distances." Nature, Volume 384, (1996).
    THE recent discoveries1-4 of massive planetary companions orbiting several solar-type stars pose a conundrum. Conventional models5,6 for the formation of giant planets (such as Jupiter and Saturn) place such objects at distances of several astronomical units from the parent star, whereas all but one of the new objects are on orbits well inside 1 AU; these planets must therefore have originated at larger distances and subsequently migrated inwards. One suggested migration mechanism invokes tidal interactions between the planet and the evolving circumstellar disk7. Such a mechanism results in planets with small, essentially circular orbits, which appears to be the case for many of the new planets. But two of the objects have substantial orbital eccentricities, which are difficult to reconcile with a tidal-linkage model. Here we describe an alternative model for planetary migration that can account for these large orbital eccentricities. If a system of three or more giant planets form about a star, their orbits may become unstable as they gain mass by accreting gas from the circumstellar disk; subsequent gravitational encounters among these planets can eject one from the system while placing the others into highly eccentric orbits both closer and farther from the star
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  7. #6  
    Forum Ph.D. Wolf's Avatar
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    As I suspected. We're probably right, and this is either a capture or decaying-orbit problem.

    Still, it'd be interesting to see what happens with it. I mean, if it's destruction takes longer or shorter than expected, then we've got something new going on. :P
    Wolf
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