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Osiris, a chthonian planet - a very physical hell?

  1. Feb 6, 2004 #1

    Nereid

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    A gas giant planet, its hydrogen and helium having been substantially ripped from it, is now having its CNO bones flayed by the UV and high temperature whips of its parent...

    "The planet, called HD 209458b, may sound familiar. It is already an extrasolar planet with an astounding list of firsts: the first extrasolar planet discovered transiting its sun, the first with an atmosphere, the first observed to have an evaporating hydrogen atmosphere (in 2003 by the same team of scientists) and now the first to have an atmosphere containing oxygen and carbon. Furthermore the 'blow-off' effect observed by the team during their October and November 2003 observations with Hubble had never been seen before. "

    http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=34567

    Not exactly the expanding earth of notnewton ...
     
  2. jcsd
  3. Feb 7, 2004 #2

    wolram

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    its encouraging that free oxygen has been detected,
    i was wondering if i should keep the seti program on
    my pc this article has convinced me to keep it.
     
  4. Feb 10, 2004 #3

    Nereid

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    aka 'the blowing in the wind' planet

    ... and its shape - as measured at the top of the atmosphere - resembles a rugby ball ...
    http://skyandtelescope.com/news/article_1172_1.asp
     
  5. Feb 29, 2004 #4
    I first read about HD 209458 b a few months ago and was completely fascinated by the discovery. After googleing around a bit I became curious: just how long has this planet been evaporating? (and how much mass has it lost during it’s tortured history?)

    One source gives an age for the system as 4 to 6 GA:

    http://obswww.unige.ch/~udry/planet/hd209458.html

    Hhmmmm. These error bars are too large for the purposes of my questions. This next source makes a commitment and narrows the age estimate to 5.2 GA.

    http://www2.iap.fr/exoplanetes/tab_hd209458_e.html

    I had considered, then rejected the possibility that the planet was cranked in-system recently (relatively speaking). I’m not saying it’s impossible, just unlikely. You’d need another giant planet to interact with and shrink its (HD 209458 b) orbit.

    The scenario I view as much more likely is that HD 209458 b migrated in-system pre-ignition and has been dumping mass throughout the life-time of the system.

    As if the question wasn’t hairy enough to begin with, I realized that as the overall mass decreased, so too the roche limit, and almost certainly the rate of evaporation.

    So, my question is: What was the original mass of HD 209458 b? For some reason my brain likes the figure “10 to 12 Jup masses”. I mean, 5.2 billion years is a long ass time. I feel as if I’m within arms reach of the answer but lack the math skills to connect the dots. I found a site which provides what I assume to be a set of equations for calc-ing evaporation of giant planet atmospheres in general.

    http://www2.iap.fr/exoplanetes/tenerife.pdf

    With the info found in these links, is it possible to estimate (even roughly) the original mass of HD 209458 b?
     
  6. Feb 29, 2004 #5

    Nereid

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    First, what is the current rate of mass loss for the planet?

    Next, assume the mass loss was no greater, for any significant portion of the planet's life.

    Then, multiply the mass loss by the planet's age, and you have an OOM upper limit estimate of the planet's original mass.

    To improve your estimate by a significant factor, you will need to list the effects that may have had a significant impact on the mass loss between formation and today, make an OOM estimate of each effect's likely size given a range of reasonable parameters (some will likely give a higher mass loss, some a lower, and some may be more or less neutral), rank the list, and examine the top few in some detail (it's likely that ~< 5 effects will really matter).
     
  7. Mar 3, 2004 #6
    SETI no, but life... maybe

    Ever consider the harsh conditions that life survives under in Earth, life found at the most hostile conditions at our poles, and life found at high ocean pressures next to venting volcanic activity.

    If there is life of intelligence out there, then they will know to get the hell away from this Osiris planet
     
  8. Mar 9, 2004 #7
    Nereid wrote:

    “First, what is the current rate of mass loss for the planet?”

    According to several sources (including the second link you provided), the current rate of mass loss is estimated to be 10,000 tons per/sec. What is frustratingly absent is any detailed explanation concerning how this was determined. I can still accept this as a provisional working figure for now. The second link further states:

    “The planet HD 209458b appears to shed gas at such a high rate that it could lose up to 10 percent of its mass during its lifetime.”

    This seems like a conservative estimate to me but I can’t demonstrate how or why. Again, no detail on how they arrived at this figure. I guess I’ll have to hit the university stacks and track down the original paper by Vidal-Madjar et al.

    Nereid wrote:

    “To improve your estimate by a significant factor, you will need to list the effects that may have had a significant impact on the mass loss between formation and today”

    This is where I run into my own wall of ignorance. Again. The planet’s proximity to the primary dictates that a combination of tidal-gravitational influences should yield an atmospheric shape which is somewhat lobate. Does this also apply to the Roche limit? I think so but lack certainty. I have to remind myself that the Roche limit is not some physical osmotic membrane, but merely a bounding cavity. (higher density within, lower density without) I assume that gas may escape at equal rates at all points of the Roche limit. Or is this a mistaken assumption? Would escape rates increase at the lobes? (one pointing toward the primary, the other pointing away)

    Next, I assume that lighter elements disassociate (under the barrage of the stellar wind) more readily than heavier elements. If this is true, then the rate of mass loss would definitely be affected over time as the lighter elements cooked off.

    Lastly, the T-Tauri phase must have been at least 100 times more intense than the current era. The duration of this phase could be as little as 3 my or as long as 10 my. For any precision I’ll need to know how long the primary took to settle onto the main sequence.

    PS. What is “OOM”?
     
  9. Mar 9, 2004 #8

    marcus

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    Order Of Magnitude AFAIK :smile:
     
  10. Mar 16, 2004 #9

    Nereid

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    There is, IIRC, data on the absorption by hydrogen when the planet crosses the line of sight to us. The most direct way to determine the mass loss is to assume it's hydrogen (He and 'metals' can be added later; assume all molecules containing H are dissociated), and that the H observed has escaped from Osiris.
    Yes, or the on-line preprints, ...
    Good. I would only add the time it took for Osiris to form, when it formed (cf when the primary formed), and the extent of any migration towards the primary. In any case, work on this should be postponed until you have a better handle on your 0-order estimates.
    order of magnitude, just as marcus said
     
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