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Re: [comets-ml] comet C/2009 P1 Garradd

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  • jbortle@aol.com
    In regard to recent posts, I would like to offer that the activity Comet Garrard reportedly is experiencing currently would not, under normal circumstances, be
    Message 1 of 11 , Jul 10, 2011
      In regard to recent posts, I would like to offer that the activity Comet
      Garrard reportedly is experiencing currently would not, under normal
      circumstances, be regarded as any sort of "outburst". By the descriptions offered
      it seems more likely to be just a simple and not unexpected brightening
      phase with the comet's approach to perihelion.

      There are basically three difference scenarios that can result in the rapid
      enhancement of the brightness of a comet, but I would add that, being
      comets, there will always be a few unique exceptions! That being said, the
      three classic rapid brightening scenarios can be roughly outlined as follows:

      1. A progressive, often fairly predictable, overall rapid brightening that
      results from a comet's approach to the Sun, the Earth, or both. When both
      r and delta are rather quickly decreasing this brightening can sometimes
      indeed manifest itself rather dramatically (recall Hyakutake's Great Comet?).
      This type of brightening scenario is generally accompanied by the degree
      of condensation remaining either relatively unchanged, or slowly increasing
      by one, or two units over time. The coma itself will likely seem to expand,
      while its surface brightness steadily increases relatively in step with a
      power-law formula as applied to r and delta.

      2. There is the "brightness surge", which can be even more dramatic
      (sometimes even observationally striking) and for those not familiar with the
      comets that exhibit these, truly amazing to see. They consists of a steady
      rise in overall surface brightness over a week, or 10 days, accompanied by a
      startling increase in coma diameter, along with a slowly increasing DC. This
      sort of event results from a combination of situations. First, the comet's
      nucleus actually does abruptly become somewhat more active, perhaps when
      the comet's primary active region first comes into sunlight(?). At the same
      time, there is also a perception situation. The initially weak, faint and
      diffuse central region seems to almost explosively expand outward as an ever
      growing low surface brightness disk and the entire object seems to
      brighten up. The comet can increase in m1 by sometimes two, three, or even four
      magnitudes and become huge in just a few days! Often different observers will
      report wildly differing coma diameters and thus highly conflicting m1
      values at this stage which are clearly dependant on their local sky brightness.
      Much of the apparent brightening and dramatic coma expansion actually is
      the result of the pre-existing, very faint, outer coma of the comet, now
      being enhanced at least somewhat by new nucleus out gassing, progressively
      rising above the brightness of the sky background and becoming visible to
      observers. Several periodic comets exhibit this form of activity in the extreme
      during their final weeks (or days) just before perihelion passage.
      Probably the best example of this sort of phenomenon is seen in regard to
      P/d'Arrest, especially when its geocentric distance is under about 0.75AU.

      3. Finally, there is the true "outburst" which is usually characterized by
      the abrupt appearance of a bright, initially almost star-like, body in the
      comet's nuclear region. This unusually intense feature will, in following
      days, rapidly evolve into a small disk, shell, or expanding wave of
      brightening. This feature over a relatively short time will expand and grow slowly
      more diffuse until it fills, and its brightness overwhelms, the entire
      fainter pre-existing coma. Such events are relatively uncommon and typified by
      the striking displays seen in conjunction with such objects as P/S-W1 and
      P/Holmes. Long period comets can display somewhat similar phenomena, but
      generally these are less visually dramatic events.

      J.Bortle





      [Non-text portions of this message have been removed]
    • gvnn64
      Thanks John, I was just wandering if there was any way to define a common background concept for the outburst phase of a comet, and how to distinguish it
      Message 2 of 11 , Jul 10, 2011
        Thanks John, I was just wandering if there was any way to define a common background concept for the "outburst" phase of a comet, and how to distinguish it from any other similar episodes frequently reported by the observers.
        .
        Bye,
        Giovanni Sostero

        --- In comets-ml@yahoogroups.com, jbortle@... wrote:
        >
        > In regard to recent posts, I would like to offer that the activity Comet
        > Garrard reportedly is experiencing currently would not, under normal
        > circumstances, be regarded as any sort of "outburst". By the descriptions offered
        > it seems more likely to be just a simple and not unexpected brightening
        > phase with the comet's approach to perihelion.
        >
        > There are basically three difference scenarios that can result in the rapid
        > enhancement of the brightness of a comet, but I would add that, being
        > comets, there will always be a few unique exceptions! That being said, the
        > three classic rapid brightening scenarios can be roughly outlined as follows:
        >
        > 1. A progressive, often fairly predictable, overall rapid brightening that
        > results from a comet's approach to the Sun, the Earth, or both. When both
        > r and delta are rather quickly decreasing this brightening can sometimes
        > indeed manifest itself rather dramatically (recall Hyakutake's Great Comet?).
        > This type of brightening scenario is generally accompanied by the degree
        > of condensation remaining either relatively unchanged, or slowly increasing
        > by one, or two units over time. The coma itself will likely seem to expand,
        > while its surface brightness steadily increases relatively in step with a
        > power-law formula as applied to r and delta.
        >
        > 2. There is the "brightness surge", which can be even more dramatic
        > (sometimes even observationally striking) and for those not familiar with the
        > comets that exhibit these, truly amazing to see. They consists of a steady
        > rise in overall surface brightness over a week, or 10 days, accompanied by a
        > startling increase in coma diameter, along with a slowly increasing DC. This
        > sort of event results from a combination of situations. First, the comet's
        > nucleus actually does abruptly become somewhat more active, perhaps when
        > the comet's primary active region first comes into sunlight(?). At the same
        > time, there is also a perception situation. The initially weak, faint and
        > diffuse central region seems to almost explosively expand outward as an ever
        > growing low surface brightness disk and the entire object seems to
        > brighten up. The comet can increase in m1 by sometimes two, three, or even four
        > magnitudes and become huge in just a few days! Often different observers will
        > report wildly differing coma diameters and thus highly conflicting m1
        > values at this stage which are clearly dependant on their local sky brightness.
        > Much of the apparent brightening and dramatic coma expansion actually is
        > the result of the pre-existing, very faint, outer coma of the comet, now
        > being enhanced at least somewhat by new nucleus out gassing, progressively
        > rising above the brightness of the sky background and becoming visible to
        > observers. Several periodic comets exhibit this form of activity in the extreme
        > during their final weeks (or days) just before perihelion passage.
        > Probably the best example of this sort of phenomenon is seen in regard to
        > P/d'Arrest, especially when its geocentric distance is under about 0.75AU.
        >
        > 3. Finally, there is the true "outburst" which is usually characterized by
        > the abrupt appearance of a bright, initially almost star-like, body in the
        > comet's nuclear region. This unusually intense feature will, in following
        > days, rapidly evolve into a small disk, shell, or expanding wave of
        > brightening. This feature over a relatively short time will expand and grow slowly
        > more diffuse until it fills, and its brightness overwhelms, the entire
        > fainter pre-existing coma. Such events are relatively uncommon and typified by
        > the striking displays seen in conjunction with such objects as P/S-W1 and
        > P/Holmes. Long period comets can display somewhat similar phenomena, but
        > generally these are less visually dramatic events.
        >
        > J.Bortle
        >
        >
        >
        >
        >
        > [Non-text portions of this message have been removed]
        >
      • Hiroki Akisawa
        Dear All, I calculated the direction of dust tail of C/2009 P1. For example, July 9, 23:42 UT: http://homepage2.nifty.com/akisawa2/C2009P1_20110709.jpg You can
        Message 3 of 11 , Jul 11, 2011
          Dear All,

          I calculated the direction of dust tail of C/2009 P1.

          For example, July 9, 23:42 UT:
          http://homepage2.nifty.com/akisawa2/C2009P1_20110709.jpg

          You can compare with Rolando's image:
          http://tech.groups.yahoo.com/group/comets-ml/message/17602

          So, I think the left side tail is usually dust tail.

          best regards
          Hiroki Akisawa, Japan
        • Hiroki Akisawa
          Dear All, ... I m sorry... So, I think the left side tail is un-usually dust tail. best regards Hiroki Akisawa, Japan ... To: comets-ml@yahoogroups.com From:
          Message 4 of 11 , Jul 11, 2011
            Dear All,

            > So, I think the left side tail is usually dust tail.

            I'm sorry...

            So, I think the left side tail is un-usually dust tail.

            best regards
            Hiroki Akisawa, Japan


            ----- Original Message -----
            To: comets-ml@yahoogroups.com
            From: Hiroki Akisawa <hce02635@...>
            Date: Tue, 12 Jul 2011 10:35:49 +0900 (JST)
            Subject: Re: [comets-ml] comet C/2009 P1 Garradd


            Dear All,

            I calculated the direction of dust tail of C/2009 P1.

            For example, July 9, 23:42 UT:
            http://homepage2.nifty.com/akisawa2/C2009P1_20110709.jpg

            You can compare with Rolando's image:
            http://tech.groups.yahoo.com/group/comets-ml/message/17602

            So, I think the left side tail is usually dust tail.

            best regards
            Hiroki Akisawa, Japan
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