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ISON prospects

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  • David Seargent
    Hi all, All recent upgrades of the orbit of this comet give weakly hyperbolic eccentricities, suggesting that it is coming in from Oort Cloud distances and is
    Message 1 of 8 , Feb 20, 2013
      Hi all,
      All recent upgrades of the orbit of this comet give weakly hyperbolic eccentricities, suggesting that it is coming in from Oort Cloud distances and is probably making its first (and only?) close approach of the Sun. The small possibility that it is a �dynamically rejuvenated� rather than a �dynamically new� comet (i.e. a long-period object that has had its aphelion distance increased to Oort Cloud remoteness at an earlier perihelion passage) seems improbable in view of the current activity far from the Sun. There must be something more volatile than water ice at the surface of the nucleus, which seems unlikely if the comet had experienced previous episodes of fierce heating at sunskirting distances.
      Accordingly, the brightness development of this comet will probably be similar to that of 2011 L4; fairly steep until about 1.7 AU (late September in this instance) followed by a very slow increase until perihelion. Taking fairly representative values of �n� (5 initially and 2.5 after the �break� in the light curve) and fitting them to recent observations has the comet barely brighter than magnitude 5 in mid-November, about -4 or -5 near perihelion and first magnitude or better in early December. Northern observers should see a moderately bright comet most probably sporting a very long and intense tail. For us in the south however, it seems as though it will be marginally naked-eye at best. Hopefully though, it will emulate L4 in having a nice bright dust tail before perihelion and make a very nice show in binoculars!
      Cheers,
      David

      [Non-text portions of this message have been removed]
    • cnj999
      Sadly, over recent weeks I ve reluctantly come to agree with David s current interpretation of the situation. For a long time I had anticipated that as the
      Message 2 of 8 , Feb 21, 2013
        Sadly, over recent weeks I've reluctantly come to agree with David's
        current interpretation of the situation. For a long time I had anticipated that
        as the comet's orbital elements were progressively refined that "e" would
        eventually drop ever so slightly below 1.0 and some sort of relationship
        with the 1680 comet could be established. Clearly this is not happening.

        At the same time a re-interpretation of ISON as being a dynamically "new"
        comet potentially creates a need to totally re-evaluate all our initial
        prognostications for this comet's future development. The assumption up until
        recently has been that ISON had an absolute magnitude of around 5.0-5.5
        (visually) that would likely be maintained through perihelion, making it in
        truth a big healthy comet. However, if we now make an analogy with PanSTARRS,
        then once below a heliocentric distance of 1.5 a.u., or so, we could be
        dealing with an object having an intrinsic brightness that possibly places it
        in, or close to, the marginal perihelion survivability range. Clearly this
        could change the entire game. In my experience an absolute magnitude of
        about +6.5 is the minimum for dynamically "old" sungrazer/sunskirter
        survival. Could we potentially now be dealing with another Comet Wilson-Hubbard,
        or Lovejoy?

        J.Bortle



        In a message dated 2/21/2013 1:45:10 A.M. Eastern Standard Time,
        seargent@... writes:


        Hi all,
        All recent upgrades of the orbit of this comet give weakly hyperbolic
        eccentricities, suggesting that it is coming in from Oort Cloud distances and
        is probably making its first (and only?) close approach of the Sun. The small
        possibility that it is a “dynamically rejuvenated” rather than a “
        dynamically new” comet (i.e. a long-period object that has had its aphelion
        distance increased to Oort Cloud remoteness at an earlier perihelion passage)
        seems improbable in view of the current activity far from the Sun. There must
        be something more volatile than water ice at the surface of the nucleus,
        which seems unlikely if the comet had experienced previous episodes of fierce
        heating at sunskirting distances.

        Cheers,
        David



        [Non-text portions of this message have been removed]
      • Alain Jo Motte
        Has someone any idea of the accuracy of the calculations by Encke in 1818 for C/1680 V1. The orbit may be very poorly defined, due to the bad quality of the
        Message 3 of 8 , Feb 21, 2013
          Has someone any idea of the accuracy of the calculations by Encke in 1818
          for C/1680 V1.
          The orbit may be very poorly defined, due to the bad quality of the
          observations in 1680.
          Is there any chance left that C/2012 S1 ISON may be the sister of C/1680 V1
          ?

          Alain-Jo

          -----Message d'origine-----
          From: jbortle@...
          Sent: Thursday, February 21, 2013 3:37 PM
          To: comets-ml@yahoogroups.com
          Subject: Re: [comets-ml] ISON prospects

          Sadly, over recent weeks I've reluctantly come to agree with David's
          current interpretation of the situation. For a long time I had anticipated
          that
          as the comet's orbital elements were progressively refined that "e" would
          eventually drop ever so slightly below 1.0 and some sort of relationship
          with the 1680 comet could be established. Clearly this is not happening.

          At the same time a re-interpretation of ISON as being a dynamically "new"
          comet potentially creates a need to totally re-evaluate all our initial
          prognostications for this comet's future development. The assumption up
          until
          recently has been that ISON had an absolute magnitude of around 5.0-5.5
          (visually) that would likely be maintained through perihelion, making it in
          truth a big healthy comet. However, if we now make an analogy with
          PanSTARRS,
          then once below a heliocentric distance of 1.5 a.u., or so, we could be
          dealing with an object having an intrinsic brightness that possibly places
          it
          in, or close to, the marginal perihelion survivability range. Clearly this
          could change the entire game. In my experience an absolute magnitude of
          about +6.5 is the minimum for dynamically "old" sungrazer/sunskirter
          survival. Could we potentially now be dealing with another Comet
          Wilson-Hubbard,
          or Lovejoy?

          J.Bortle



          In a message dated 2/21/2013 1:45:10 A.M. Eastern Standard Time,
          seargent@... writes:


          Hi all,
          All recent upgrades of the orbit of this comet give weakly hyperbolic
          eccentricities, suggesting that it is coming in from Oort Cloud distances
          and
          is probably making its first (and only?) close approach of the Sun. The
          small
          possibility that it is a “dynamically rejuvenated” rather than a “
          dynamically new” comet (i.e. a long-period object that has had its aphelion
          distance increased to Oort Cloud remoteness at an earlier perihelion
          passage)
          seems improbable in view of the current activity far from the Sun. There
          must
          be something more volatile than water ice at the surface of the nucleus,
          which seems unlikely if the comet had experienced previous episodes of
          fierce
          heating at sunskirting distances.

          Cheers,
          David



          [Non-text portions of this message have been removed]



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        • David Seargent
          Hi Alain-jo, By today s standards, Encke s calculations would leave a lot to be desired because the data he had to work with was not of the sort of accuracy
          Message 4 of 8 , Feb 23, 2013
            Hi Alain-jo,
            By today's standards, Encke's calculations would leave a lot to be desired because the data he had to work with was not of the sort of accuracy that we normally have nowadays. The period of the 1680 comet may, accordingly, be longer than the 8,000-9,000 years or thereabouts traditionally given and it is not impossible that this was a new comet. In this respect, it is interesting to note that S. K. Vsekhsvyatskii computed the value of "n" for the comet's light-curve as 2.08 between discovery and perihelion. This is very much as expected for a new comet following the "break" in the light-curve (which in this instance would have taken place prior to discovery). After perihelion, he calculated an "n" of 3.36. The corresponding values for absolute magnitude were 4.4 and 3.7, implying a possible minor surge after perihelion albeit coupled with a steeper decline. Maybe the comet split at perihelion (no real evidence for this, although one observer noted that the condensation appeared multiple. It is not known whether this was a real multiple nucleus or something else).
            As regards a real relationship with ISON, the latter seems pretty certainly to be dynamically new. The orbits of ISON and 1680 come close at perihelion, but diverge at greater distances, so if the comets are related, ISON must have split away at a prior passage close to the Sun. This, however, is not possible if either comet is dynamically new. By definition, a dynamically new comet could not have previously passed close enough to the Sun to be active. It seems therefore that the comets are not in any way related and that the similarity in orbital elements is pure coincidence!
            Regards,
            David



            To: comets-ml@yahoogroups.com
            From: alain-jo.motte@...
            Date: Thu, 21 Feb 2013 18:24:09 +0100
            Subject: Re: [comets-ml] ISON prospects






            Has someone any idea of the accuracy of the calculations by Encke in 1818
            for C/1680 V1.
            The orbit may be very poorly defined, due to the bad quality of the
            observations in 1680.
            Is there any chance left that C/2012 S1 ISON may be the sister of C/1680 V1
            ?

            Alain-Jo

            -----Message d'origine-----
            From: jbortle@...
            Sent: Thursday, February 21, 2013 3:37 PM
            To: comets-ml@yahoogroups.com
            Subject: Re: [comets-ml] ISON prospects

            Sadly, over recent weeks I've reluctantly come to agree with David's
            current interpretation of the situation. For a long time I had anticipated
            that
            as the comet's orbital elements were progressively refined that "e" would
            eventually drop ever so slightly below 1.0 and some sort of relationship
            with the 1680 comet could be established. Clearly this is not happening.

            At the same time a re-interpretation of ISON as being a dynamically "new"
            comet potentially creates a need to totally re-evaluate all our initial
            prognostications for this comet's future development. The assumption up
            until
            recently has been that ISON had an absolute magnitude of around 5.0-5.5
            (visually) that would likely be maintained through perihelion, making it in
            truth a big healthy comet. However, if we now make an analogy with
            PanSTARRS,
            then once below a heliocentric distance of 1.5 a.u., or so, we could be
            dealing with an object having an intrinsic brightness that possibly places
            it
            in, or close to, the marginal perihelion survivability range. Clearly this
            could change the entire game. In my experience an absolute magnitude of
            about +6.5 is the minimum for dynamically "old" sungrazer/sunskirter
            survival. Could we potentially now be dealing with another Comet
            Wilson-Hubbard,
            or Lovejoy?

            J.Bortle

            In a message dated 2/21/2013 1:45:10 A.M. Eastern Standard Time,
            seargent@... writes:

            Hi all,
            All recent upgrades of the orbit of this comet give weakly hyperbolic
            eccentricities, suggesting that it is coming in from Oort Cloud distances
            and
            is probably making its first (and only?) close approach of the Sun. The
            small
            possibility that it is a �dynamically rejuvenated� rather than a �
            dynamically new� comet (i.e. a long-period object that has had its aphelion
            distance increased to Oort Cloud remoteness at an earlier perihelion
            passage)
            seems improbable in view of the current activity far from the Sun. There
            must
            be something more volatile than water ice at the surface of the nucleus,
            which seems unlikely if the comet had experienced previous episodes of
            fierce
            heating at sunskirting distances.

            Cheers,
            David

            [Non-text portions of this message have been removed]

            ------------------------------------

            *** Comets Mailing List Important Contributions : ***
            ***
            http://tech.groups.yahoo.com/group/comets-ml/files/Important%20Contributions/
            ***

            Comet Observations List: http://groups.yahoo.com/group/CometObs/
            Comet Images List: http://groups.yahoo.com/group/Comet-Images/

            NOTICE: Material quoted or re-posted from the Comets Mailing List should be
            indicated by:

            Comets Mailing List [date]
            http://www.yahoogroups.com/group/comets-ml
            Yahoo! Groups Links






            [Non-text portions of this message have been removed]
          • terryjlovejoy
            Kazuo Kinoshita ( http://jcometobs.web.fc2.com/cmt/k12s1.htm ) has calculated the original orbit for C/2012 S1 to be a very long ellipse with a period of
            Message 5 of 8 , Feb 24, 2013
              Kazuo Kinoshita ( http://jcometobs.web.fc2.com/cmt/k12s1.htm ) has calculated the original orbit for C/2012 S1 to be a very long ellipse with a period of around 6 million years. This puts it's aphelion well and truly in the Oort cloud with a future orbit ejecting it from the solar system.

              I'm glad David and John have put some balance on the hype around this Comet. David himself puts forth some good arguments in his Sungrazer eBook that even a very brilliant comet like C/1882 R1 did not exceed mag -12 to -13 at perihelion. He also points out that few if any of the Sunskirting comets of recent centuries became easy daylight objects, including Comet Seki-Lines which was not seen at all around perihelion. It will certainly be exciting to see how this plays out, but I'm certainly not expecting anything of full moon brightness.

              Terry
            • Piotr A. Dybczyński
              Hi, ... Please take into account, that it seems to be to early to obtain definitive orbit of C/2012 S1. Some hints you can find here:
              Message 6 of 8 , Feb 25, 2013
                Hi,

                > As regards a real relationship with ISON, the latter seems pretty
                > certainly to be dynamically new.

                Please take into account, that it seems to be to early to obtain
                definitive orbit of C/2012 S1. Some hints you can find here:

                http://apollo.astro.amu.edu.pl/PAD/index.php?n=WikicometPub.2012S1

                Regards,
                Piotr
                --
                /**************************************************************************
                Dr Piotr A. Dybczynski, Astronomical Observatory, A.Mickiewicz University
                homepage: http://apollo.astro.amu.edu.pl/PAD e-mail: dybol@...
                ********************************************************************PAD***/
              • cnj999
                At least until some folks began to throw the term Sungrazer around loosely, it indeed rightfully denoted specifically members of the long recognized Kreutz
                Message 7 of 8 , Aug 3, 2013
                  At least until some folks began to throw the term "Sungrazer" around
                  loosely, it indeed rightfully denoted specifically members of the long
                  recognized Kreutz sungrazing family of comets. And this is absolutely the ONLY group
                  of objects that the name should indicate, as they represent a clearly
                  singular type of comet, exhibiting a physical behavior pattern that separates
                  them from other comets.

                  The proper term applicable to ISON and potentially similar objects would
                  be "sun-skirter", of which there have been a handful over the centuries. All
                  behaved in ways that illustrated their difference from true Sungrazers.
                  The only exception was the Great Comet of 1680, about which several
                  authorities have expressed the well based opinion that it was in some manner
                  directly related to/evolved from the Kreutz sungrazing group itself.

                  In short, Comet ISON not a sungrazer, it is a sun-skirter, and should not
                  be termed so.

                  J.Bortle




                  In a message dated 8/3/2013 5:54:06 A.M. Eastern Daylight Time,
                  pachacoti@... writes:




                  Hi Rob,

                  > Very much agree -- especially with "sundancers" (ISON not a sungrazer).

                  I'm pretty curious about how you define "sungrazer". In my knowledge this
                  term remains ill-defined all the time. The perihelion of comet ISON already
                  falls within the Roche Limit of the sun and thus it will be subject to
                  tidal disruption then. "Sungrazer" should not be privileged to Kreutz group
                  comets only.

                  Man-To
                  --------------------------------------------------
                  Man-To Hui (Cantonese)
                  Wentao Xu, Wen-Tao Hsu (Mandarin Chinese)
                  Astrosite: comethunter.lamost.org
                  Blog: pachacoti.wordpress.com





                  [Non-text portions of this message have been removed]
                • Ervin Fleming
                  Makes sense but I would interject this thought. The term sungrazer has been around for a long time and I don t think it will be easily expunged from usage. It
                  Message 8 of 8 , Aug 3, 2013
                    Makes sense but I would interject this thought. The term sungrazer has been around for a long time and I don't think it will be easily expunged from usage. It may be worth the effort to differentiate by using the term "Kreutz Sungrazer" for that category and "sungrazer" generically for close approaching comets.  I don't think sun-skirter will overwhelm current usage.....  This for official communications with the unenlightened media.
                    Tom


                    ________________________________
                    From: "jbortle@..." <jbortle@...>
                    To: comets-ml@yahoogroups.com
                    Sent: Saturday, August 3, 2013 8:05 AM
                    Subject: Re: [comets-ml] ISON prospects


                     

                    At least until some folks began to throw the term "Sungrazer" around
                    loosely, it indeed rightfully denoted specifically members of the long
                    recognized Kreutz sungrazing family of comets. And this is absolutely the ONLY group
                    of objects that the name should indicate, as they represent a clearly
                    singular type of comet, exhibiting a physical behavior pattern that separates
                    them from other comets.

                    The proper term applicable to ISON and potentially similar objects would
                    be "sun-skirter", of which there have been a handful over the centuries. All
                    behaved in ways that illustrated their difference from true Sungrazers.
                    The only exception was the Great Comet of 1680, about which several
                    authorities have expressed the well based opinion that it was in some manner
                    directly related to/evolved from the Kreutz sungrazing group itself.

                    In short, Comet ISON not a sungrazer, it is a sun-skirter, and should not
                    be termed so.

                    J.Bortle




                    In a message dated 8/3/2013 5:54:06 A.M. Eastern Daylight Time,
                    mailto:pachacoti%40ymail.com writes:

                    Hi Rob,

                    > Very much agree -- especially with "sundancers" (ISON not a sungrazer).

                    I'm pretty curious about how you define "sungrazer". In my knowledge this
                    term remains ill-defined all the time. The perihelion of comet ISON already
                    falls within the Roche Limit of the sun and thus it will be subject to
                    tidal disruption then. "Sungrazer" should not be privileged to Kreutz group
                    comets only.

                    Man-To
                    --------------------------------------------------
                    Man-To Hui (Cantonese)
                    Wentao Xu, Wen-Tao Hsu (Mandarin Chinese)
                    Astrosite: comethunter.lamost.org
                    Blog: pachacoti.wordpress.com

                    [Non-text portions of this message have been removed]




                    [Non-text portions of this message have been removed]
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