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Re: [comets-ml] Fw: C/2011L4 questions, and answers

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  • cnj999
    Denis - Uwe Pilz interpretation of the situation re PanSTARRS current appearance is essentially correct. In my opinion comet 2011 L4 looks precisely like what
    Message 1 of 1 , Apr 19, 2013
      Denis - Uwe Pilz interpretation of the situation re PanSTARRS' current
      appearance is essentially correct. In my opinion comet 2011 L4 looks precisely
      like what would typically be anticipated for a very dust-rich comet under
      the prevailing viewing geometry.

      The comet is not displaying any sort of actual antitail, or anomalous
      tail. What is seen is simply a continuous fan of material with no clearly
      independent/separate sunward-pointing feature. The tail is best classified as
      just a very broad dust tail of Type II, or combined Type II and III in terms
      of the old nomenclature. Actually, we have seen a number of such situations
      presented in fainter comets over the past decade, or two, and I think many
      here may well recall some of them.

      From the Earth's perspective the comet is very close to being situated
      diametrically on the opposite side of the Sun from us. Therefore, material
      trailing the nucleus is viewed with the comet's orbital plane presented
      virtually edge-on and the material is seen projecting away from us (just the
      opposite of the situation with Comet Arend-Roland in 1957).

      The general appearance of PanSTARRS' tail does not even require the
      heaviest of the dust to actually lay along precisely the same orbital track as
      the nucleus. Rather, it can be located a significant distance beyond the
      orbital track of the nucleus and be curving away. It is simply our view along
      the line of sight in the orbital plane that gives the current impression.
      Even if truly gently curving away from the nucleus it will appear from our
      current vantage point as presenting a straight line of demarcation along the
      tail's boundary. If some of our imagers would include large and precise
      orientation marks on their photos it would help in ascertaining approximately
      how much beyond the comet's actual orbital track the extreme trailing edge
      of the dust tail material lies.

      Concerning the near lack of an ion tail for Comet PanSTARRS, this
      exemplifies just how drastically low the gas-to-dust ratio has been for this comet.
      Evidence of an ion tail did present itself, if only briefly, during the
      interval when the comet was nearest its perihelion passage. Take look at
      several of the images uploaded near to that time in our ML image page, there an
      weak ion tail will be seen.

      Incidentally, I believe that I had voiced my concern about this lack of
      evidence of any high gas production long before the comet brightened up and
      its likely implications for an ultimately poor performance post-T (the same
      seems currently true for Comet ISON as well).

      J.Bortle




      In a message dated 4/18/2013 4:48:20 P.M. Eastern Daylight Time,
      buczynski8166@... writes:






      -----Original Message-----
      From: denis buczynski
      Sent: Thursday, April 18, 2013 9:47 PM
      To: COML ; BAA Comets discussion list
      Subject: C/2011L4 questions

      Hello all,
      Could anyone on this list answer a few questions about this comet's
      physical appearance.
      Firstly, has there been an estimate of the physical size of the nucleus?
      2) How much dust has been released from the nucleus to maintain the large
      fan tail we have seen and
      imaged for so long. Also has spectroscopy revealed the nature of the
      material released from the
      nucleus.
      3) Has there been a gas component imaged in the tail? The colour imaging
      has only shown a yellow fan
      with no blue gas feature.
      4) We have see and imaged the forward spike/antitail for a month or more
      now , with little change in
      the PA of this feature with respect to the comet head. I assume that as
      the viewing geometry is
      changing all the time as we are see the comet moving away from earth. Why
      is the PA of this forward
      spike/antitail not changing with time? On Comet Arend- Roland the antitail
      lasted only a few days
      (11 I believe) and was seen to swing round as the viewing geometry changed.
      4) What is the cause of the forward spike/antitail, is it just a question
      of viewing perspective.
      5) Has there been any specific professional observing campaign on this
      comet?

      Thank you in advance
      Denis Buczynski






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