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Re: {MPML} 136199<134340

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  • Franck Marchis
    ... Below various Pluto size measurements that I found in the literature and elsewhere. I am not sure where comes from D 2340 km for Pluto in IAU #9185. Could
    Message 1 of 60 , Nov 8, 2010
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      > ] the present observation indicates that Eris has
      > ] a diameter < 2320 km -- therefore smaller than Pluto, whose
      > ] diameter is > 2340 km.
      > I wouldn't be so certain that Pluto is larger than 2340 km.
      > There was an interesting presentation at the 2010 DPS meeting
      > about a model for Pluto's troposphere that yielded a diameter
      > much closer to our mutual event value near 2300 km. Unfortunately,
      > their fitted diameter isn't in the abstract, and I failed to jot
      > down the number presented at DPS. I do remember commenting on how
      > I liked the result because of how close it was to our mutual event result.

      Below various Pluto size measurements that I found in the literature and elsewhere.
      I am not sure where comes from D>2340 km for Pluto in IAU #9185. Could you clarify?

      Bulk Properties of Pluto and Charon
      D=2290-2400 km

      Tholen et al., 1987b. D.J. Tholen, M.W. Buie and C.E. Swift, Circumstances for Pluto-Charon mutual events in 1987. Astron. J. 93 (1987b), pp. 244–247. Full Textvia CrossRef
      D=2290 km

      Tholen et al., 1987c. D.J. Tholen, M.W. Buie and C.E. Swift, Circumstances for Pluto-Charon mutual events in 1988. Astron. J. 94 (1987c), pp. 1681–1685. Full Text via CrossRef
      D=2244 km

      Buie et al. 2006
      "assuming a radius of 1152 +/- 10 km" (D=2304 +/- 20 km)
      footnote 2: "Choosing a value for the radius of Pluto is not a simple matter. Current measurements from mutual events and stellar occultations do not completely agree, and explanations of the differences depend on the models chosen to interpret the data. Here we use the number adopted in most Pluto map-fitting projects with an error bar chosen to include the range of model values for the radius from mutual event and stellar occultation data."

      Large changes in Pluto's atmosphere as revealed by recent stellar occultations
      no size reported or I missed it.

      Charon/Pluto Mass Ratio Obtained with HST CCD Observations in 1991 and 1993
      see Table 16
      Mutual event TB90 -> D=2302 +/- 12 km
      Mutual event YB94 -> D= 2352 +/- 12 km
      EY92 Stellar Occ -> D = 2412 /-22 km
      A94 HST FOC images -> D= 2320 km

      Pluto's lower atmosphere structure and methane abundance from high-resolution spectroscopy and stellar occultations
      D= 2336 km

      D=2350 km

      D=2304 km
      from Buie et al. 2006

      Solar View
      D=2274 km

      an old but interesting review

      There are more of them...

      --- Franck Marchis, Ph.D. -----------
      Planetary Astronomer
      SETI Institute & UC-Berkeley
      Phone +1 650 810 0236 or +1 510 642 3928
      "C'est drole les cons, ca repose; c'est comme le feuillage au milieu des roses" (J.-L. Dabadie)

    • Marshall Eubanks
      Ah, thanks for catching that... Marshall
      Message 60 of 60 , Nov 9, 2010
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        Ah, thanks for catching that...


        On Nov 9, 2010, at 8:24 PM, Paulo Holvorcem wrote:

        > Just a correction: Eris has a 561-year orbit and is now past aphelion
        > at 96.6 AU from the sun. The famous, large distant object with a period
        > longer than 10,000 years orbit and which is moving toward perihelion is
        > Sedna.
        > Paulo
        > On 2010-11-09 23:06, Marshall Eubanks wrote:
        >> On Nov 9, 2010, at 5:46 PM, RICHARD MILES wrote:
        >>> This is where chemistry is important. Usually people consider nitrogen
        >>> frost and methane frost at the distance of Pluto but the temperature out
        >>> there at 96 AU is probably low enough to have solid hydrogen frost even in a
        >>> near-vacuum. You don't need a large mass fraction to be present to alter
        >>> the appearance of the surface so the fact the bulk density of Eris is high
        >>> is not so critical. How about a world near the surface having geysers of
        >>> liquid hydrogen and where on a cold day it snows flakes of solid hydrogen?
        >> First, there is this press report from the DPS
        >> http://www.astronomynow.com/news/n1010/06eris/
        >> Second, remember that Eris is in spring moving towards summer on its 10+ kiloyear orbit.
        >> Whatever is coating the surface could be a relatively recent deposition .
        >> Has anyone done thermal models to see if Hydrogen could freeze in winter to evaporate at the sub-solar point as summer approaches ?
        >> Regards
        >> Marshall
        > ------------------------------------
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