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2012 KT42 will transit the sun

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  • Andrew Lowe
    Another possibility to observe an NEO crossing the sun? On May 29 about 10:10 UT, the minimum geocentric elongation from the center of the sun will be 0.1
    Message 1 of 8 , May 28, 2012
      Another possibility to observe an NEO crossing the sun? On May 29 about 10:10 UT, the minimum geocentric elongation from the center of the sun will be 0.1 degrees, so given the parallax there will be a transit across the sun, centered in southern Asia. Could include Europe and eastern Asia, but I won't have time to compute this.

      If the diameter is about 5m, then the object could be about 6" across against the solar disk.

      Andrew
      http://members.shaw.ca/andrewlowe/home.htm
    • Aldo Vitagliano
      ... Hi Andrew, Here is the map for the transit: http://www.webalice.it/alvitagl/Figures/KT42Tran.gif Regards Aldo
      Message 2 of 8 , May 28, 2012
        --- In mpml@yahoogroups.com, "Andrew Lowe" <andrew.lowe@...> wrote:
        >
        > Another possibility to observe an NEO crossing the sun? On May 29 about 10:10 UT, the minimum geocentric elongation from the center of the sun will be 0.1 degrees, so given the parallax there will be a transit across the sun, centered in southern Asia. Could include Europe and eastern Asia, but I won't have time to compute this.
        >
        > If the diameter is about 5m, then the object could be about 6" across against the solar disk.
        >

        Hi Andrew,

        Here is the map for the transit:
        http://www.webalice.it/alvitagl/Figures/KT42Tran.gif

        Regards
        Aldo
      • Andrew Lowe
        The transit will occur at the zenith in Egypt, with a duration of 12 minutes. Since the apparent size could be half that of a Mercury transit, the object may
        Message 3 of 8 , May 28, 2012
          The transit will occur at the zenith in Egypt, with a duration of 12 minutes. Since the apparent size could be half that of a Mercury transit, the object may be visible with optical aid. Observers in the Middle East take note!

          Of course additional astrometry to refine the event would be welcome.

          Andrew

          > Hi Andrew,
          >
          > Here is the map for the transit:
          > http://www.webalice.it/alvitagl/Figures/KT42Tran.gif
          >
          > Regards
          > Aldo
          >
        • Andrew Lowe
          Ignore my comment about observing the transit. As Aldo points out, the size will be 0.006 , not 6 ... Andrew
          Message 4 of 8 , May 28, 2012
            Ignore my comment about observing the transit. As Aldo points out, the size will be 0.006", not 6"...

            Andrew

            --- In mpml@yahoogroups.com, "Andrew Lowe" <andrew.lowe@...> wrote:
            >
            > The transit will occur at the zenith in Egypt, with a duration of 12 minutes. Since the apparent size could be half that of a Mercury transit, the object may be visible with optical aid. Observers in the Middle East take note!
            >
            > Of course additional astrometry to refine the event would be welcome.
            >
            > Andrew
            >
            > > Hi Andrew,
            > >
            > > Here is the map for the transit:
            > > http://www.webalice.it/alvitagl/Figures/KT42Tran.gif
            > >
            > > Regards
            > > Aldo
            > >
            >
          • Dave Tholen
            ... That s even larger than Apophis will be on 2029 April 13, yet this object is almost two orders of magnitude smaller than Apophis, which means it would have
            Message 5 of 8 , May 28, 2012
              > If the diameter is about 5m, then the object could be about 6" across
              > against the solar disk.

              That's even larger than Apophis will be on 2029 April 13, yet this
              object is almost two orders of magnitude smaller than Apophis, which
              means it would have to get almost two orders of magnitude closer to
              subtend an angle as large as Apophis.

              A nice number to keep in your head is 206265, the number of arcsec
              in a radian.

              6" / 206265" = 0.000029

              5 m / 0.000029 = 172000 m = 172 km

              Because it will pass more like 20,500 km from the center of the Earth,
              or about 14,000 km from the surface, that's about a factor of 80 farther
              away, so a factor of 80 smaller. Not knowing what the close approach
              distance uncertainty is, let's put it in the 0.07 to 0.08 arcsec range.
              Then there's the diameter uncertainty stemming from the unknown albedo.
              Not sure where the 0.006 arcsec value came from. Maybe somebody felt
              that the 6 arcsec figure came from a kilometers versus meters mistake?
            • Dave Herald
              How did the figure of 6 arc sec diameter get derived for a 5m diameter asteroid? At the time of the transit, the geocentric distance is about .0008AU, or about
              Message 6 of 8 , May 29, 2012
                How did the figure of 6 arc sec diameter get derived for a 5m diameter asteroid?

                At the time of the transit, the geocentric distance is about .0008AU, or about 120,000km (about 1/3 of the lunar distance). At that distance, 5 meters equates to about 9mas – far far too small to be visible in transit. If you are in doubt about this – ask yourself whether in your scope you can see things that are 15meters across on the surface of the moon....

                May I suggest that someone lost track of powers of 10, and derived the apparent diameter based on the asteroid being 5_km_ in diameter.... oops!


                Dave Herald
                Murrumbateman, Australia


                From: Aldo Vitagliano
                Sent: Tuesday, May 29, 2012 3:10 AM
                To: mpml@yahoogroups.com
                Subject: {MPML} Re: 2012 KT42 will transit the sun


                --- In mpml@yahoogroups.com, "Andrew Lowe" <andrew.lowe@...> wrote:
                >
                > Another possibility to observe an NEO crossing the sun? On May 29 about 10:10 UT, the minimum geocentric elongation from the center of the sun will be 0.1 degrees, so given the parallax there will be a transit across the sun, centered in southern Asia. Could include Europe and eastern Asia, but I won't have time to compute this.
                >
                > If the diameter is about 5m, then the object could be about 6" across against the solar disk.
                >

                Hi Andrew,

                Here is the map for the transit:
                http://www.webalice.it/alvitagl/Figures/KT42Tran.gif

                Regards
                Aldo




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

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                Posts to this list or information found within may be freely used, with the stipulation that MPML and the originating author are cited as the source of the information.Yahoo! Groups Links




                [Non-text portions of this message have been removed]
              • Robert M. Elowitz
                From: mpml@yahoogroups.com [mailto:mpml@yahoogroups.com] On Behalf Of Dave Herald Sent: Tuesday, May 29, 2012 4:03 AM To: mpml@yahoogroups.com; Aldo Vitagliano
                Message 7 of 8 , May 29, 2012
                  From: mpml@yahoogroups.com [mailto:mpml@yahoogroups.com] On Behalf Of Dave Herald
                  Sent: Tuesday, May 29, 2012 4:03 AM
                  To: mpml@yahoogroups.com; Aldo Vitagliano
                  Subject: Re: {MPML} Re: 2012 KT42 will transit the sun



                  For a 5 meter asteroid at a distance of 120000 km, its apparent angular diameter would be

                  calculated as



                  theta = (5 m / 1.20E8) * 206265 = 0.0086 arcsec



                  I would think you would need a telescope with a 30 meter primary aperture to see this event.



                  How did the figure of 6 arc sec diameter get derived for a 5m diameter asteroid?

                  At the time of the transit, the geocentric distance is about .0008AU, or about 120,000km (about 1/3 of the lunar distance). At that distance, 5 meters equates to about 9mas – far far too small to be visible in transit. If you are in doubt about this – ask yourself whether in your scope you can see things that are 15meters across on the surface of the moon....

                  May I suggest that someone lost track of powers of 10, and derived the apparent diameter based on the asteroid being 5_km_ in diameter.... oops!

                  Dave Herald
                  Murrumbateman, Australia

                  From: Aldo Vitagliano
                  Sent: Tuesday, May 29, 2012 3:10 AM
                  To: mpml@yahoogroups.com <mailto:mpml%40yahoogroups.com>
                  Subject: {MPML} Re: 2012 KT42 will transit the sun

                  --- In mpml@yahoogroups.com <mailto:mpml%40yahoogroups.com> , "Andrew Lowe" <andrew.lowe@...> wrote:
                  >
                  > Another possibility to observe an NEO crossing the sun? On May 29 about 10:10 UT, the minimum geocentric elongation from the center of the sun will be 0.1 degrees, so given the parallax there will be a transit across the sun, centered in southern Asia. Could include Europe and eastern Asia, but I won't have time to compute this.
                  >
                  > If the diameter is about 5m, then the object could be about 6" across against the solar disk.
                  >

                  Hi Andrew,

                  Here is the map for the transit:
                  http://www.webalice.it/alvitagl/Figures/KT42Tran.gif

                  Regards
                  Aldo

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

                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

                  Posts to this list or information found within may be freely used, with the stipulation that MPML and the originating author are cited as the source of the information.Yahoo! Groups Links

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





                  [Non-text portions of this message have been removed]
                • amaury@spaceobs.com
                  With a substantial mylar solar filter... :) Alain
                  Message 8 of 8 , May 29, 2012
                    With a substantial mylar solar filter... :)
                    Alain


                    "Robert M. Elowitz" <elowitzr@...> a écrit :

                    >
                    >
                    >
                    >
                    > From: mpml@yahoogroups.com [mailto:mpml@yahoogroups.com] On Behalf
                    > Of Dave Herald
                    > Sent: Tuesday, May 29, 2012 4:03 AM
                    > To: mpml@yahoogroups.com; Aldo Vitagliano
                    > Subject: Re: {MPML} Re: 2012 KT42 will transit the sun
                    >
                    >
                    >
                    > For a 5 meter asteroid at a distance of 120000 km, its apparent
                    > angular diameter would be
                    >
                    > calculated as
                    >
                    >
                    >
                    > theta = (5 m / 1.20E8) * 206265 = 0.0086 arcsec
                    >
                    >
                    >
                    > I would think you would need a telescope with a 30 meter primary
                    > aperture to see this event.
                    >
                    >
                    >
                    > How did the figure of 6 arc sec diameter get derived for a 5m
                    > diameter asteroid?
                    >
                    > At the time of the transit, the geocentric distance is about
                    > .0008AU, or about 120,000km (about 1/3 of the lunar distance). At
                    > that distance, 5 meters equates to about 9mas ? far far too small to
                    > be visible in transit. If you are in doubt about this ? ask yourself
                    > whether in your scope you can see things that are 15meters across on
                    > the surface of the moon....
                    >
                    > May I suggest that someone lost track of powers of 10, and derived
                    > the apparent diameter based on the asteroid being 5_km_ in
                    > diameter.... oops!
                    >
                    > Dave Herald
                    > Murrumbateman, Australia
                    >
                    > From: Aldo Vitagliano
                    > Sent: Tuesday, May 29, 2012 3:10 AM
                    > To: mpml@yahoogroups.com <mailto:mpml%40yahoogroups.com>
                    > Subject: {MPML} Re: 2012 KT42 will transit the sun
                    >
                    > --- In mpml@yahoogroups.com <mailto:mpml%40yahoogroups.com> ,
                    > "Andrew Lowe" <andrew.lowe@...> wrote:
                    >>
                    >> Another possibility to observe an NEO crossing the sun? On May 29
                    >> about 10:10 UT, the minimum geocentric elongation from the center
                    >> of the sun will be 0.1 degrees, so given the parallax there will be
                    >> a transit across the sun, centered in southern Asia. Could include
                    >> Europe and eastern Asia, but I won't have time to compute this.
                    >>
                    >> If the diameter is about 5m, then the object could be about 6"
                    >> across against the solar disk.
                    >>
                    >
                    > Hi Andrew,
                    >
                    > Here is the map for the transit:
                    > http://www.webalice.it/alvitagl/Figures/KT42Tran.gif
                    >
                    > Regards
                    > Aldo
                    >
                    > ------------------------------------
                    >
                    > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                    >
                    > Posts to this list or information found within may be freely used,
                    > with the stipulation that MPML and the originating author are cited
                    > as the source of the information.Yahoo! Groups Links
                    >
                    > [Non-text portions of this message have been removed]
                    >
                    >
                    >
                    >
                    >
                    > [Non-text portions of this message have been removed]
                    >
                    >
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