Loading ...
Sorry, an error occurred while loading the content.

Possible tail length of P1

Expand Messages
  • JS & EJ Gifford
    Hi All, Is anyone willing to speculate on the visible tail length of P1 for us in the southern hemisphere in the days following perihelion, and thus the
    Message 1 of 6 , Jan 1, 2007
    View Source
    • 0 Attachment
      Hi All,
      Is anyone willing to speculate on the visible tail length of P1
      for us in the southern hemisphere in the days following perihelion, and
      thus the potential for any vertical tail to be seen after dusk when the
      comet is below the horizon?

      Regards, Jim Gifford.

      Bridgetown, Western Australia.
    • huihsing2004
      Hi Jim, Below some calculated results for P1. The used formulas are still experimental because of the lack of good data from comets with small perihelion
      Message 2 of 6 , Jan 2, 2007
      View Source
      • 0 Attachment
        Hi Jim,

        Below some calculated results for P1.
        The used formulas are still experimental because of the lack of good
        data from comets with small perihelion distances. Also the coma
        diameters and tail lengths are highly depending from the absolute
        magnitude of the comet (using for P1: m1= 6 + 5 log delta + 8 log
        r). Therefore the given coma diameters and tail lengths are highly
        speculative.

        Magnitude gain by forward scattering will take place when a comet,
        or better, the dust particles are placed between the observer and
        the sun and if these dust particles are of almost the same size as
        the radiation wavelength. Under very favorable circumstances, with a
        scatter angle of less than 30 degrees, it is possible that the
        brightness of a comet is increased dramatically due the forward
        scattering. The forward scattering is a property of almost all
        particles. To cause forward scattering the comet has to be within
        the orbit of the earth at a distance of less than 1 AU. However, the
        theoretical magnitude gain is highly dependent on the number and
        size of the dust particles.

        Therefore the calculated magnitude gain (in the table under Mv+) is
        speculative. The maximum of the forward scattering and magnitude
        gain of 2 magnitudes is calculated for January 14th.

        ------------------------------------
        Date Coma Tail PA Mv+
        ------------------------------------
        4 5 4 357 <0.1
        9 4 12 5 <0.1
        14 4 18 76 2.0
        19 6 11 157 0.3
        24 7 6 167 <0.1
        ------------------------------------
        Date = date fore 0h UT in Jan 2007.
        Coma = expected coma diameter in arc minutes.
        Tail = expected tail length in degrees (gas tail).
        PA = position angle in degrees (gas tail).
        Mv+ = theoretical magnitude gain by forward scattering.

        Note: The calculated results are only valid under good observational
        conditions (Limiting naked eye magnitude of about 6.0 – 6.5 at the
        altitude of the comet).

        Best regards and clear skies,

        Peter Bus, Groningen, The Netherlands.


        --- In comets-ml@yahoogroups.com, "JS & EJ Gifford" <jgifford@...>
        wrote:
        >
        > Hi All,
        > Is anyone willing to speculate on the visible tail length
        of P1
        > for us in the southern hemisphere in the days following
        perihelion, and
        > thus the potential for any vertical tail to be seen after dusk
        when the
        > comet is below the horizon?
        >
        > Regards, Jim Gifford.
        >
        > Bridgetown, Western Australia.
        >
      • huihsing2004
        Because the Tabel was indistinctly, the whole text again, Peter Bus. Hi Jim, Below some calculated results for P1. The used formulas are still experimental
        Message 3 of 6 , Jan 2, 2007
        View Source
        • 0 Attachment
          Because the Tabel was indistinctly, the whole text again, Peter Bus.

          Hi Jim,

          Below some calculated results for P1.
          The used formulas are still experimental because of the lack of good
          data from comets with small perihelion distances. Also the coma
          diameters and tail lengths are highly depending from the absolute
          magnitude of the comet (using for P1: m1= 6 + 5 log delta + 8 log
          r). Therefore the given coma diameters and tail lengths are highly
          speculative.

          Magnitude gain by forward scattering will take place when a comet,
          or better, the dust particles are placed between the observer and
          the sun and if these dust particles are of almost the same size as
          the radiation wavelength. Under very favorable circumstances, with a
          scatter angle of less than 30 degrees, it is possible that the
          brightness of a comet is increased dramatically due the forward
          scattering. The forward scattering is a property of almost all
          particles. To cause forward scattering the comet has to be within
          the orbit of the earth at a distance of less than 1 AU. However, the
          theoretical magnitude gain is highly dependent on the number and
          size of the dust particles.

          Therefore the calculated magnitude gain (in the table under Mv+) is
          speculative. The maximum of the forward scattering and magnitude
          gain of 2 magnitudes is calculated for January 14th.

          ----------------------------
          Date Coma Tail PA Mv+
          ----------------------------
          4 5 4 357 <0.1
          9 4 12 5 <0.1
          14 4 18 76 2.0
          19 6 11 157 0.3
          24 7 6 167 <0.1
          ----------------------------
          Date = date fore 0h UT in Jan 2007.
          Coma = expected coma diameter in arc minutes.
          Tail = expected tail length in degrees (gas tail).
          PA = position angle in degrees (gas tail).
          Mv+ = theoretical magnitude gain by forward scattering.

          Note: The calculated results are only valid under good observational
          conditions (Limiting naked eye magnitude of about 6.0 – 6.5 at the
          altitude of the comet).

          Best regards and clear skies,

          Peter Bus, Groningen, The Netherlands.


          --- In comets-ml@yahoogroups.com, "JS & EJ Gifford" <jgifford@...>
          wrote:
          >
          > Hi All,
          > Is anyone willing to speculate on the visible tail length
          of P1
          > for us in the southern hemisphere in the days following
          perihelion, and
          > thus the potential for any vertical tail to be seen after dusk
          when the
          > comet is below the horizon?
          >
          > Regards, Jim Gifford.
          >
          > Bridgetown, Western Australia.
          >
        • amar sharma
          ... Hello all, The above calculated table says that the gas tail is going to be visible at 18 degrees length on 14th. But can I know what is going to be the
          Message 4 of 6 , Jan 3, 2007
          View Source
          • 0 Attachment
            --- huihsing2004 <huihsing2004@...> wrote:

            > ----------------------------
            > Date Coma Tail PA Mv+
            > ----------------------------
            > 14 4 18 76 2.0
            > ----------------------------
            > Date = date fore 0h UT in Jan 2007.
            > Coma = expected coma diameter in arc minutes.
            > Tail = expected tail length in degrees (gas tail).

            Hello all,
            The above calculated table says that the 'gas'
            tail is going to be visible at 18 degrees length on
            14th. But can I know what is going to be the status or
            visibility of the dust one, if any? Currently that's
            the one being observed, so can any estimations of that
            be made? Is the gas tail dominant at this close
            distance? And the coma estimate made above, is it the
            visual one in strong twilight, or the actual size?
            (Sorry, I'm not too sure).

            Coincidentally 14th is the date it's going to be
            visible to us the best here at latitude +13 degrees,
            in the Southern part of India. Hence we have already
            made plans to get this one visually and probably
            wide-field image it if possible. It's going to be just
            5-6 degrees above the Sun, and we have a plan to start
            hunting it down early. It's on 14th that the
            McNaught-Mercury conjunction is there visible for us.

            Another question, can this get better than C/2004 F4
            Bradfield in appearance? That's the only one I feel
            like comparing to this! I never saw that except for in
            images. Please do reply. Thanking You. Amar.

            Send free SMS to your Friends on Mobile from your Yahoo! Messenger. Download Now! http://messenger.yahoo.com/download.php
          • cnj999
            ... Amar - As is usually the case for the physical development of a given comet with approach to perihelion, many variables are involved that can not easily be
            Message 5 of 6 , Jan 4, 2007
            View Source
            • 0 Attachment
              --- In comets-ml@yahoogroups.com, amar sharma <amar10sharmaa@...>
              wrote:
              >
              > --- huihsing2004 <huihsing2004@...> wrote:
              >
              > > ----------------------------
              > > Date Coma Tail PA Mv+
              > > ----------------------------
              > > 14 4 18 76 2.0
              > > ----------------------------
              > > Date = date fore 0h UT in Jan 2007.
              > > Coma = expected coma diameter in arc minutes.
              > > Tail = expected tail length in degrees (gas tail).
              >
              > Hello all,
              > The above calculated table says that the 'gas'
              > tail is going to be visible at 18 degrees length on
              > 14th. But can I know what is going to be the status or
              > visibility of the dust one, if any? Currently that's
              > the one being observed, so can any estimations of that
              > be made? Is the gas tail dominant at this close
              > distance? And the coma estimate made above, is it the
              > visual one in strong twilight, or the actual size?
              > (Sorry, I'm not too sure).
              >
              > Coincidentally 14th is the date it's going to be
              > visible to us the best here at latitude +13 degrees,
              > in the Southern part of India. Hence we have already
              > made plans to get this one visually and probably
              > wide-field image it if possible. It's going to be just
              > 5-6 degrees above the Sun, and we have a plan to start
              > hunting it down early. It's on 14th that the
              > McNaught-Mercury conjunction is there visible for us.
              >
              > Another question, can this get better than C/2004 F4
              > Bradfield in appearance? That's the only one I feel
              > like comparing to this! I never saw that except for in
              > images. Please do reply. Thanking You. Amar.
              >

              Amar - As is usually the case for the physical development of a given
              comet with approach to perihelion, many variables are involved that
              can not easily be defined beforehand.

              Because C/2006 P1 has been so poorly observed up until now, its
              absolute or intrinsic magnitude, as well as the variable "n", are
              still quite uncertain and the former figure is typically of great
              importance in the development of the tails (especially the dust
              tail). Likewise, particle size relative to sunlight pressure,
              heliocentric distance and the projection circumstances, all play
              major rolls in at least the dust tail's apparent length and curvature.

              Should Ho be about magnitude 6.5 or fainter, then the dust tail is
              likely to be fairly weakly and with no more than a few degrees of its
              length visible in the bright twilight, initially projecting in the
              same relative direction as calculated for the ion tail around the
              time of perihelion. One might well expect an appearance similar to a
              somewhat enhanced version of Ikeya-Zang, or perhaps like Bradfield
              2004 F4.

              However, if it turns out that C/2006 P1 is actually a major comet,
              with an Ho around 5 or so, the situation could change rather
              dramatically (he says, taking a deep and hesitant breath!). In that
              case, a strong, high surface brightness dust tail is likely to form.
              And at the same time, tail projection circumstances and the small q
              should favor much of the length of any dust tail to almost overlap
              the ion tail for perhaps 1/2 to 2/3's the calculated span, before
              significantly curving off to the north.

              Under the very best of circumstances, from a visual standpoint C/2006
              P1 could become a truly spectacular object (especially when factoring
              in a major forward-scattering event), with possibly a degree or more
              of tail visible in the daytime, given a really good sky. The overall
              appearance might be similar to descriptions of the brilliant Comet
              Skjellerup-Maristany in 1927, when it was viewed in daylight not far
              from the Sun.

              Immediately following sunset, the comet's head would likely appear a
              dramatic yellowish hue, due to the strong emission lines of sodium,
              as would the beginnings of the tail, this often being seen in
              conjunction with major comets at small q. The intense, almost
              straight, combined ion-dust tail might be traced 10 or more degrees
              upwards in the bright sky, with both components becoming much longer
              as twilight deepens. I would speculate that the overall impression at
              that time might be somewhat similar to that displayed after sunset by
              the Great Daylight Comet of 1910, given that the tail projection
              circumstances happen to be so favorable.

              HOWEVER, any such potential grand display is, at the moment, pure
              speculation. The next few days of twilight observations are likely to
              tell the true story. And remember, even if C/2006 P1 does develop
              dramatically, its display is likely to be rather short-lived, both
              because of the brief duration of the forward-scattering event and the
              fact that the comet swiftly moves away from the Earth after mid
              January. So...pray for universally clear weather in mid January!

              JBortle
            • Carey Johnson
              ... Astronomy Picture of the Day http://antwrp.gsfc.nasa.gov/apod/astropix.html Carey _________________________________________________________________ Find
              Message 6 of 6 , Jan 4, 2007
              View Source
              • 0 Attachment
                >HOWEVER, any such potential grand display is, at the moment, pure
                >speculation. The next few days of twilight observations are likely to
                >tell the true story. And remember, even if C/2006 P1 does develop
                >dramatically, its display is likely to be rather short-lived, both
                >because of the brief duration of the forward-scattering event and the
                >fact that the comet swiftly moves away from the Earth after mid
                >January. So...pray for universally clear weather in mid January!
                >
                >JBortle
                >


                Astronomy Picture of the Day

                http://antwrp.gsfc.nasa.gov/apod/astropix.html


                Carey

                _________________________________________________________________
                Find sales, coupons, and free shipping, all in one place! �MSN Shopping
                Sales & Deals
                http://shopping.msn.com/content/shp/?ctid=198,ptnrid=176,ptnrdata=200639
              Your message has been successfully submitted and would be delivered to recipients shortly.