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Incoming Activity of comet 107P/Wilson-Harrington?

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  • iferrinv
    Hello all: 107P/Wilson-Harrington is a comet-asteroid transition object that exhibited activity on one single night in 1949, and has remained inactive since.
    Message 1 of 15 , Nov 10, 2009
      Hello all:
      107P/Wilson-Harrington is a comet-asteroid transition object that
      exhibited activity on one single night in 1949, and has remained
      inactive since. The activity was recorded in two Palomar Observatory
      plates. The red plate did not show activity, while the blue plate
      exhibited a faint tail. This prompted Yanga Fernandez et al. to
      conclude that the comet had an ion tail. The interesting thing
      is that the activity took place 41 days after perihelion. Well,
      the comet has just passed perihelion and 41 days will take place
      next December 4th, 3 WEEKS FROM NOW! The present email is to
      alert you of the possibility of a new outburst of this object
      next month, and to request your help in securing observations to
      confirm or deny its activity. The comet was recovered by Sostero
      et al. last year. Currently is at magnitude 14-15 and will be
      magnitude 13-14 in December so it is within reach of small
      telescopes in the morning sky just before sunrise. If the
      comet does not show activity then we can declare it dead, and
      by itself this is an important result. So please make an effort
      to make CCD observations of this object in V, R or without filter,
      and let me know about your work sending me an email at
      ferrin@.... You can see the light curve of this object in
      the "Atlas of Secular Light Curves of Comets",

      http://arxiv.org/ftp/arxiv/papers/0909/0909.3498.pdf

      Additional information and the call for observations will be
      posted in my web site

      http://webdelprofesor.ula.ve/ciencias/ferrin

      Clear skies to all.

      Ignacio Ferrín,
      Center for Fundamental Physics,
      University of the Andes,
      Mérida, Venezuela
      +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    • P. Clay Sherrod
      This is an excellent reminder, but I hesitate to agree that if we do not see activity this December that we can declare it dead. With its past, there is
      Message 2 of 15 , Nov 10, 2009
        This is an excellent reminder, but I hesitate to agree that if we do not see activity this
        December that we "can declare it dead." With its past, there is always potential for some
        outgassing without warning nor without specifics to position or orientation. Without a
        doubt it is an unusual object and we are not at all certain of the nature of its makeup,
        be it cometary or asteroidal.

        Thanks for posting this; a very good target with some potential.

        Clay
        _____
        Dr. P. Clay Sherrod
        Arkansas Sky Observatories
        MPC H45 - Petit Jean Mountain South
        MPC H41 - Petit Jean Mountain
        MPC H43 - Conway West
        http://www.arksky.org/

        ----- Original Message -----
        From: "iferrinv" <ferrin@...>
        To: <comets-ml@yahoogroups.com>
        Sent: Tuesday, November 10, 2009 12:25 PM
        Subject: [comets-ml] Incoming Activity of comet 107P/Wilson-Harrington?


        Hello all:
        107P/Wilson-Harrington is a comet-asteroid transition object that
        exhibited activity on one single night in 1949, and has remained
        inactive since. The activity was recorded in two Palomar Observatory
        plates. The red plate did not show activity, while the blue plate
        exhibited a faint tail. This prompted Yanga Fernandez et al. to
        conclude that the comet had an ion tail. The interesting thing
        is that the activity took place 41 days after perihelion. Well,
        the comet has just passed perihelion and 41 days will take place
        next December 4th, 3 WEEKS FROM NOW! The present email is to
        alert you of the possibility of a new outburst of this object
        next month, and to request your help in securing observations to
        confirm or deny its activity. The comet was recovered by Sostero
        et al. last year. Currently is at magnitude 14-15 and will be
        magnitude 13-14 in December so it is within reach of small
        telescopes in the morning sky just before sunrise. If the
        comet does not show activity then we can declare it dead, and
        by itself this is an important result. So please make an effort
        to make CCD observations of this object in V, R or without filter,
        and let me know about your work sending me an email at
        ferrin@.... You can see the light curve of this object in
        the "Atlas of Secular Light Curves of Comets",

        http://arxiv.org/ftp/arxiv/papers/0909/0909.3498.pdf

        Additional information and the call for observations will be
        posted in my web site

        http://webdelprofesor.ula.ve/ciencias/ferrin

        Clear skies to all.

        Ignacio Ferrín,
        Center for Fundamental Physics,
        University of the Andes,
        Mérida, Venezuela
        +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++





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

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      • Alan Hale
        Dear Ignacio, and all, It is good to have a timely reminder that this object is now in prime viewing position for detecting possible activity. It is nearest
        Message 3 of 15 , Nov 10, 2009
          Dear Ignacio, and all,

          It is good to have a timely reminder that this object is now in prime
          viewing position for detecting possible activity. It is nearest Earth (0.379
          AU) on November 19; this is the closest it has been to Earth since 1979
          (when it was re-discovered by Helin et al.) and the closest approach it
          makes until 2039. Unfortunately, this is not as close an approach as one
          might like, but we have to work with what nature gives us.

          I don't believe there is anything magical about the "41 days" -- if it is
          going to exhibit activity, it could theoretically do so at any time. (For
          that matter, we don't know whether or not it was active prior to its
          discovery in 1949.) It has not exhibited any activity (that we know of,
          anyway) at any subsequent return (at least, since 1979) so that in itself
          gets rid of any significance behind any particular timeframe with respect to
          perihelion. Incidentally, the red plate in 1949 does show the tail; it's
          very faint (and on the DSS image you have to enhance the contrast -- but it
          is there); the tail is obvious on the blue image.

          107P is now in the evening sky, around 20h 50m, -11d, elongation 84 degrees.
          The recent CCD magnitudes that have been published on the DOU MPECs are
          indicating a magnitude of 16 to 17. Visually, I have so far been unable to
          detect it (fainter than mag ~15.2); I've just cleaned my optical system and
          am waiting for a very clear night to try it again.


          Sincerely,

          Alan
        • RICHARD MILES
          Ignacio, Thanks for alerting the comet community. I agree that during the next few weeks it is worth monitoring this asteroid (4105) for activity. My
          Message 4 of 15 , Nov 10, 2009
            Ignacio,

            Thanks for alerting the comet community. I agree that during the next few
            weeks it is worth monitoring this asteroid (4105) for activity. My
            interpretation of the bluish ion tail in 1949 was that it was caused by a
            particularly energetic solar flare which sputtered material off of the
            asteroids surface and not that it was volatile material finding its way from
            within the nucleus. I have already started observations of (4015). Here's
            an extract of a report made on November 04:

            >> A tracked and stacked set of 6 x 90 sec images taken with the B filter in
            >> a dark sky on the 2.0-m Faulkes Telescope South on 2009 November 04 at
            >> 10:19UT of 'Comet 107P' at a solar elongation of 80 deg two weeks past
            >> perihelion shows no evidence of cometary activity. Likewise for a single
            >> R-filter image. (R.Miles) <<

            Just to illustrate the point that this is a particularly favourable
            perihelic return of the 'comet', here are the approx. distances from the
            Earth at each of its perihelic returns since first discovered:

            Year Delta
            1949 0.20 AU
            1954 1.8 AU
            1958 1.8 AU
            1962 0.5 AU
            1966 1.1 AU
            1971 2.0 AU
            1975 1.3 AU
            1979 0.15 AU
            1984 1.7 AU
            1988 1.8 AU
            1992 0.50 AU
            1997 1.2 AU
            2001 2.0 AU
            2005 1.1 AU
            2009 0.38 AU

            BTW: Concerning its brightness, I think you are over-estimating this. My
            photometry using 7 CMC-14 reference stars on Nov 4 10:09 UT gave R=17.01 +/-
            0.05. The V magnitude predicted by JPL Horizons for this epoch is 16.71 and
            that it will be brightest at V=16.37 on November 27.

            Richard Miles
            British Astronomical Association

            ----- Original Message -----
            From: "iferrinv" <ferrin@...>
            To: <comets-ml@yahoogroups.com>
            Sent: Tuesday, November 10, 2009 6:25 PM
            Subject: [comets-ml] Incoming Activity of comet 107P/Wilson-Harrington?


            Hello all:
            107P/Wilson-Harrington is a comet-asteroid transition object that
            exhibited activity on one single night in 1949, and has remained
            inactive since. The activity was recorded in two Palomar Observatory
            plates. The red plate did not show activity, while the blue plate
            exhibited a faint tail. This prompted Yanga Fernandez et al. to
            conclude that the comet had an ion tail. The interesting thing
            is that the activity took place 41 days after perihelion. Well,
            the comet has just passed perihelion and 41 days will take place
            next December 4th, 3 WEEKS FROM NOW! The present email is to
            alert you of the possibility of a new outburst of this object
            next month, and to request your help in securing observations to
            confirm or deny its activity. The comet was recovered by Sostero
            et al. last year. Currently is at magnitude 14-15 and will be
            magnitude 13-14 in December so it is within reach of small
            telescopes in the morning sky just before sunrise. If the
            comet does not show activity then we can declare it dead, and
            by itself this is an important result. So please make an effort
            to make CCD observations of this object in V, R or without filter,
            and let me know about your work sending me an email at
            ferrin@.... You can see the light curve of this object in
            the "Atlas of Secular Light Curves of Comets",

            http://arxiv.org/ftp/arxiv/papers/0909/0909.3498.pdf

            Additional information and the call for observations will be
            posted in my web site

            http://webdelprofesor.ula.ve/ciencias/ferrin

            Clear skies to all.

            Ignacio Ferrín,
            Center for Fundamental Physics,
            University of the Andes,
            Mérida, Venezuela
          • Matson, Robert D.
            I was tempted to try 107P from SSO (0.61-m, no filter) during this lunation and stack a bunch of 90-second images. On clear nights, I routinely get down to
            Message 5 of 15 , Nov 10, 2009
              I was tempted to try 107P from SSO (0.61-m, no filter) during this
              lunation and stack a bunch of 90-second images. On clear nights,
              I routinely get down to magnitude +20.3 using this scope with a
              120-second integration time, so I would think it would have no
              problem showing cometary activity if present.

              But if the 2-meter Faulkes saw no such activity a week ago, I
              wonder if it's even worth trying with less than 1/10th the
              aperture area. --Rob

              -----Original Message-----
              From: mpml@yahoogroups.com [mailto:mpml@yahoogroups.com] On Behalf Of
              RICHARD MILES
              Sent: Tuesday, November 10, 2009 2:14 PM
              To: comets-ml@yahoogroups.com
              Cc: Edward Gomez; mpml@yahoogroups.com
              Subject: {MPML} Re: [comets-ml] Incoming Activity of comet
              107P/Wilson-Harrington?

              Ignacio,

              Thanks for alerting the comet community. I agree that during the next
              few weeks it is worth monitoring this asteroid (4105) for activity. My
              interpretation of the bluish ion tail in 1949 was that it was caused by
              a particularly energetic solar flare which sputtered material off of the
              asteroids surface and not that it was volatile material finding its way
              from within the nucleus. I have already started observations of (4015).
              Here's an extract of a report made on November 04:

              >> A tracked and stacked set of 6 x 90 sec images taken with the B
              >> filter in a dark sky on the 2.0-m Faulkes Telescope South on 2009
              >> November 04 at 10:19UT of 'Comet 107P' at a solar elongation of 80
              >> deg two weeks past perihelion shows no evidence of cometary activity.

              >> Likewise for a single R-filter image. (R.Miles) <<

              Just to illustrate the point that this is a particularly favourable
              perihelic return of the 'comet', here are the approx. distances from the
              Earth at each of its perihelic returns since first discovered:

              Year Delta
              1949 0.20 AU
              1954 1.8 AU
              1958 1.8 AU
              1962 0.5 AU
              1966 1.1 AU
              1971 2.0 AU
              1975 1.3 AU
              1979 0.15 AU
              1984 1.7 AU
              1988 1.8 AU
              1992 0.50 AU
              1997 1.2 AU
              2001 2.0 AU
              2005 1.1 AU
              2009 0.38 AU

              BTW: Concerning its brightness, I think you are over-estimating this.
              My photometry using 7 CMC-14 reference stars on Nov 4 10:09 UT gave
              R=17.01 +/- 0.05. The V magnitude predicted by JPL Horizons for this
              epoch is 16.71 and that it will be brightest at V=16.37 on November 27.

              Richard Miles
              British Astronomical Association
            • gvnn64@libero.it
              Dear Richard and all. ... In the few instances where asteroidal object have shown discontinuous signs of cometary activity (e.g. the so called main belt
              Message 6 of 15 , Nov 11, 2009
                Dear Richard and all.

                > My
                > interpretation of the bluish ion tail in 1949 was that it was caused by a
                > particularly energetic solar flare which sputtered material off of the
                > asteroids surface and not that it was volatile material finding its way from
                > within the nucleus.

                In the few instances where asteroidal object have shown discontinuous signs of cometary activity (e.g. the so called "main belt comets"), dust and not gases were considered to be responsable of the observed tails. All the evidences rules out the presence of ion tails...

                Some interesting readings:
                http://adsabs.harvard.edu/abs/2009MNRAS.399L..79P
                http://adsabs.harvard.edu/abs/2009DPS....41.2003J
                http://adsabs.harvard.edu/abs/2009AJ....137.4313J
                ect.

                With kind regards,
                Giovanni Sostero
              • Juan Lacruz
                Dear all, In the case of non-main belt, NEO comets like 107P (apollo) and 162P (amor) the tails have been found to be of Ionic nature (107P Yanga Fernandez et
                Message 7 of 15 , Nov 11, 2009
                  Dear all,

                  In the case of non-main belt, NEO comets like 107P (apollo) and 162P (amor)
                  the tails have been found to be of Ionic nature (107P Yanga Fernandez et
                  al., 162P Seiichi Yoshida).

                  Intermitent activity was detected in the case of 162P, if observations do
                  not show activity that wouldn't ensure the object is dead.

                  Others consider the posibility of ignition triggered by colisions with
                  meteoroids.

                  Regards
                  Juan



                  On Wed, Nov 11, 2009 at 9:40 AM, gvnn64@... <gvnn64@...> wrote:

                  >
                  >
                  > Dear Richard and all.
                  >
                  >
                  > > My
                  > > interpretation of the bluish ion tail in 1949 was that it was caused by a
                  >
                  > > particularly energetic solar flare which sputtered material off of the
                  > > asteroids surface and not that it was volatile material finding its way
                  > from
                  > > within the nucleus.
                  >
                  > In the few instances where asteroidal object have shown discontinuous signs
                  > of cometary activity (e.g. the so called "main belt comets"), dust and not
                  > gases were considered to be responsable of the observed tails. All the
                  > evidences rules out the presence of ion tails...
                  >
                  > Some interesting readings:
                  > http://adsabs.harvard.edu/abs/2009MNRAS.399L..79P
                  > http://adsabs.harvard.edu/abs/2009DPS....41.2003J
                  > http://adsabs.harvard.edu/abs/2009AJ....137.4313J
                  > ect.
                  >
                  > With kind regards,
                  > Giovanni Sostero
                  >
                  >
                  >



                  --
                  Eppur si muove
                  ------------------------------------------------------------
                  Site http://www.lacanada.es
                  Nature http://lacanadawx.blogspot.com
                  Astro http://asteroblog.blogspot.com
                  Meteors http://cometeors.blogspot.com


                  [Non-text portions of this message have been removed]
                • RICHARD MILES
                  Dear Giovanni, Some meteorites and presumably asteroids contain a significant proportion of hydrated minerals. Energetic particles from a solar flare would
                  Message 8 of 15 , Nov 11, 2009
                    Dear Giovanni,

                    Some meteorites and presumably asteroids contain a significant proportion of
                    hydrated minerals. Energetic particles from a solar flare would dissociate
                    the water of hydration liberating it to form a temporary ion tail.

                    Following my suggestion, today I checked the database at:
                    ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_FLARES/HALPHA_FLARES/earlierdata/opt1949
                    which contains the worldwide H-alpha solar flare records for 1949.

                    Comet 107P was discovered on an image taken on 1949 November 19. Turns out
                    that the second-most active series of solar flares during the entire year
                    took place on Nov 18-19 !!
                    (The most active day for flares was on August 5).

                    I rest my case.
                    Richard Miles

                    ----- Original Message -----
                    From: <gvnn64@...>
                    To: "comets-ml" <comets-ml@yahoogroups.com>
                    Sent: Wednesday, November 11, 2009 8:40 AM
                    Subject: Re: [comets-ml] Incoming Activity of comet 107P/Wilson-Harrington?


                    > Dear Richard and all.
                    >
                    >> My
                    >> interpretation of the bluish ion tail in 1949 was that it was caused by a
                    >> particularly energetic solar flare which sputtered material off of the
                    >> asteroids surface and not that it was volatile material finding its way
                    >> from
                    >> within the nucleus.
                    >
                    > In the few instances where asteroidal object have shown discontinuous
                    > signs of cometary activity (e.g. the so called "main belt comets"), dust
                    > and not gases were considered to be responsable of the observed tails. All
                    > the evidences rules out the presence of ion tails...
                    >
                    > Some interesting readings:
                    > http://adsabs.harvard.edu/abs/2009MNRAS.399L..79P
                    > http://adsabs.harvard.edu/abs/2009DPS....41.2003J
                    > http://adsabs.harvard.edu/abs/2009AJ....137.4313J
                    > ect.
                    >
                    > With kind regards,
                    > Giovanni Sostero
                  • gvnn64@libero.it
                    Dear Richard yours is a fashinating working hypothesis (as there are many others). Obviously, without a robust experimental support, I m afraid it will remain
                    Message 9 of 15 , Nov 11, 2009
                      Dear Richard
                      yours is a fashinating working hypothesis (as there are many others). Obviously, without a robust experimental support, I'm afraid it will remain as such.
                      With kind regards,
                      Giovanni
                    • RICHARD MILES
                      Giovanni, I guess this is how science works, people come forward with options for working hypotheses and these are then compared with experimental observation.
                      Message 10 of 15 , Nov 11, 2009
                        Giovanni,

                        I guess this is how science works, people come forward with options for
                        working hypotheses and these are then compared with experimental
                        observation. In this case, I am flagging the possibility that some
                        asteroids in comet-like orbits when struck by energetic particles
                        originating from a major solar flare will have water molecules ejected from
                        otherwise stable hydrated minerals. It might be a worthwhile exercise to
                        test this in an ultrahigh vacuum chamber in the laboratory. Certainly the
                        energy of some particles emitted from the Sun is sufficient to sputter and
                        erode the surface on the molecular scale.

                        If the hypothesis is valid then we would expect other low-albedo asteroidal
                        objects in comet-like orbits, which spend only a small fraction of their
                        life close to the Sun, to exhibit similar behaviour when exposed to
                        highly-energetic particles arising from solar flares. So, for observers
                        like ourselves, we should consider monitoring those few comet-like objects
                        as they make their perihelion passage around the time of the next solar
                        maximum since one might then discover another 'comet' of this type. One
                        requirement for success is that the object would need to be relatively close
                        to the Earth for the emitted material to be detected. In the case of 107P
                        at the time of discovery, it was really quite close at about 0.22 AU.

                        btw: A definitive study of the case of 107P was published in:

                        Icarus, Volume 128, Issue 1, July 1997, Pages 114-126
                        Analysis of POSS Images of Comet-Asteroid Transition Object 107P/1949 W1
                        (Wilson-Harrington)
                        Yanga R. Fernández, Lucy A. McFadden, Carey M. Lisse, Eleanor F. Helin and
                        Alan B. Chamberlin
                        http://adsabs.harvard.edu/abs/1997Icar..128..114F

                        I have only been able to read the abstract online. I would imagine that in
                        their discussion they would have mooted a similar hypothesis to the one I am
                        suggesting.

                        Cheers,
                        Richard

                        P.S. It's a pity that the Sun is so inactive at present.

                        ----- Original Message -----
                        From: <gvnn64@...>
                        To: "comets-ml" <comets-ml@yahoogroups.com>
                        Cc: "comets-ml" <comets-ml@yahoogroups.com>; "mpml" <mpml@egroups.com>
                        Sent: Wednesday, November 11, 2009 9:56 AM
                        Subject: Re: [comets-ml] Incoming Activity of comet 107P/Wilson-Harrington?


                        > Dear Richard
                        > yours is a fascinating working hypothesis (as there are many others).
                        > Obviously, without a robust experimental support, I'm afraid it will
                        > remain as such.
                        > With kind regards,
                        > Giovanni
                      • iferrinv
                        I agree with Richard Miles that this is how science works. So it is fascinating to see so many hypothesis poping up. In this regard I would like to point out
                        Message 11 of 15 , Nov 11, 2009
                          I agree with Richard Miles that this is how science works.
                          So it is fascinating to see so many hypothesis poping up.
                          In this regard I would like to point out two things:

                          (1) The activity may have been triggered by a) the thermal
                          wave penetrating inside the nucleus and activating a deep
                          layer of ice. This hypothesis finds support from the
                          fact that the activity was observed +42 days *after*
                          perihelion. Or b) the pole of the comet is pointing to the sun
                          at +42 days after perihelion. Then there is no night and
                          the amount of solar energy received is maximum.

                          (2) The critical observing period starts next december 4th.
                          So please try to make an effort to observe from that day
                          onward. In a previous posting Clay Sherrod and Alan Hale
                          suggested that the activity may take place at any time.
                          They may be correct. We really do not know. The pole
                          position may have shifted, the deep layer may have
                          been exhausted, etc. So we should be observing for as long
                          as possible.

                          I am already plotting the secular light curve of this
                          object in 2009 and I will have it available soon. Please
                          let me know of your magnitudes to place them in the plot.
                          Robert Mason and all, go ahead with your observations. The
                          object deserved all our attention. In the Atlas of Secular
                          Light Curves this comet has a photometric age of 760 comet
                          years, so it is a methuselah comet. The question is if it
                          is dead or alive.

                          Kind Regards,

                          Ignacio
                          Center for Fundamental Physics,
                          University of the Andes,
                          Merida, Venezuela

                          +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                          --- In comets-ml@yahoogroups.com, "RICHARD MILES" <rmiles.btee@...> wrote:
                          >
                          > Giovanni,
                          >
                          > I guess this is how science works, people come forward with options for
                          > working hypotheses and these are then compared with experimental
                          > observation. In this case, I am flagging the possibility that some
                          > asteroids in comet-like orbits when struck by energetic particles
                          > originating from a major solar flare will have water molecules ejected from
                          > otherwise stable hydrated minerals. It might be a worthwhile exercise to
                          > test this in an ultrahigh vacuum chamber in the laboratory. Certainly the
                          > energy of some particles emitted from the Sun is sufficient to sputter and
                          > erode the surface on the molecular scale.
                          >
                          > If the hypothesis is valid then we would expect other low-albedo asteroidal
                          > objects in comet-like orbits, which spend only a small fraction of their
                          > life close to the Sun, to exhibit similar behaviour when exposed to
                          > highly-energetic particles arising from solar flares. So, for observers
                          > like ourselves, we should consider monitoring those few comet-like objects
                          > as they make their perihelion passage around the time of the next solar
                          > maximum since one might then discover another 'comet' of this type. One
                          > requirement for success is that the object would need to be relatively close
                          > to the Earth for the emitted material to be detected. In the case of 107P
                          > at the time of discovery, it was really quite close at about 0.22 AU.
                          >
                          > btw: A definitive study of the case of 107P was published in:
                          >
                          > Icarus, Volume 128, Issue 1, July 1997, Pages 114-126
                          > Analysis of POSS Images of Comet-Asteroid Transition Object 107P/1949 W1
                          > (Wilson-Harrington)
                          > Yanga R. Fernández, Lucy A. McFadden, Carey M. Lisse, Eleanor F. Helin and
                          > Alan B. Chamberlin
                          > http://adsabs.harvard.edu/abs/1997Icar..128..114F
                          >
                          > I have only been able to read the abstract online. I would imagine that in
                          > their discussion they would have mooted a similar hypothesis to the one I am
                          > suggesting.
                          >
                          > Cheers,
                          > Richard
                          >
                          > P.S. It's a pity that the Sun is so inactive at present.
                          >
                          > ----- Original Message -----
                          > From: <gvnn64@...>
                          > To: "comets-ml" <comets-ml@yahoogroups.com>
                          > Cc: "comets-ml" <comets-ml@yahoogroups.com>; "mpml" <mpml@egroups.com>
                          > Sent: Wednesday, November 11, 2009 9:56 AM
                          > Subject: Re: [comets-ml] Incoming Activity of comet 107P/Wilson-Harrington?
                          >
                          >
                          > > Dear Richard
                          > > yours is a fascinating working hypothesis (as there are many others).
                          > > Obviously, without a robust experimental support, I'm afraid it will
                          > > remain as such.
                          > > With kind regards,
                          > > Giovanni
                          >
                        • Alan Hale
                          Hi everyone, I am happy to see this worthwhile discussion on this most interesting object, and like the other posters I would encourage physical observation
                          Message 12 of 15 , Nov 11, 2009
                            Hi everyone,

                            I am happy to see this worthwhile discussion on this most interesting
                            object, and like the other posters I would encourage physical observation
                            attempts of all kinds while it is currently well-placed and near Earth.

                            There is one point I tried to make which, upon re-reading my earlier post,
                            may not have been as clear as I had thought:

                            The comet was discovered on photographs taken November 19, 1949. We do not
                            know, however, what its activity level was prior to that date; it
                            conceivably could have been active days, perhaps even weeks or months, prior
                            to that date, and we simply didn't know that since the comet's existence
                            wasn't yet known. We should probably keep this in mind now, both when
                            planning observing strategies as well as in formulating explantions for the
                            activity.

                            For what it's worth, I made another unsuccessful visual attempt last night.
                            My sky conditions probably weren't the greatest, but on the other hand I now
                            have a very clean optical system. Assuming a stellar object, the "comet" is
                            certainly no brighter than "m1" ~15.3, and probably a few tenths fainter
                            than that. This is, of course, consistent with the DOU MPECs as well as with
                            the photometry that has been reported in this forum.


                            Sincerely,

                            Alan
                          • gvnn64@libero.it
                            Dear Ignacio and all. ... Science works on data and experimental facts, and here we have only *one* observational evidence about a certain occurence. Then,
                            Message 13 of 15 , Nov 11, 2009
                              Dear Ignacio and all.

                              > I agree with Richard Miles that this is how science works.

                              Science works on data and experimental facts, and here we have only *one* observational evidence about a certain occurence.
                              Then, anyone can propose nearly any theory to explain such unique event, and it would be very difficult to accept or refuse it, just relying over one sporadic observation.

                              I agree that more observations are needed.

                              Giovanni
                            • Charles Bell
                              (4015) Wilson-Harrington was an object of study by the Midcourse Space Experiment (MSX) mission Mission images are available in the Planetary Data System MSX
                              Message 14 of 15 , Nov 11, 2009
                                (4015) Wilson-Harrington was an object of study by the Midcourse Space Experiment (MSX) mission

                                Mission images are available in the Planetary Data System MSX Small Bodies Images data set:

                                "Kraemer, K., Lisse, C.M., Price, S., Mizuno, D., Walker, R.G., Farnham, T.L., and Makinen, T., MSX Small Bodies Images. MSX-C-SPIRIT3-3-MSXSB-V1.0. NASA Planetary Data System, 2005."

                                http://www.psi.edu/pds/resource/msxsb.html

                                in this directory:
                                http://www.psi.edu/pds/asteroid/MSX_C_SPIRIT3_3_MSXSB_V1_0/data/wilsonh/


                                There is an on line article about this mission:

                                MIDCOURSE SPACE EXPERIMENT OBSERVATIONS OF SMALL SOLAR SYSTEM BODIES by KATHLEEN E. KRAEMER, C. M. LISSE, STEPHAN D. PRICE,D. MIZUNO, R. G. WALKER,T. L. FARNHAM,5 AND T. MÄKINEN, 2005

                                http://www.iop.org/EJ/article/1538-3881/130/5/2363/204596.text.html

                                Figure 15 text gives a summary

                                MSX images of the asteroid-comet transition object (4015) P/Wilson-Harrington taken on 1997 January 6 (left) and 10 (right). The target was detected at 8.3 m on both days, at 14.7 m on January 10, but not at the other wavelengths on either day. There is no apparent extension of the image due to an extended dust atmosphere.
                                http://www.iop.org/EJ/article/1538-3881/130/5/2363/204596.fg15.html
                              • iferrinv
                                Giovanni is correct, of course. Ignacio
                                Message 15 of 15 , Nov 16, 2009
                                  Giovanni is correct, of course.

                                  Ignacio

                                  --- In comets-ml@yahoogroups.com, "gvnn64\@...\.it" <gvnn64@...> wrote:
                                  >
                                  > Dear Ignacio and all.
                                  >
                                  > > I agree with Richard Miles that this is how science works.
                                  >
                                  > Science works on data and experimental facts, and here we have only *one* observational evidence about a certain occurence.
                                  > Then, anyone can propose nearly any theory to explain such unique event, and it would be very difficult to accept or refuse it, just relying over one sporadic observation.
                                  >
                                  > I agree that more observations are needed.
                                  >
                                  > Giovanni
                                  >
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