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Countdown to 500 Comets: no. 500

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  • Alan Hale
    Comet Lovejoy C/2011 W3 Made it to 500! My project completed comet is, on one hand, one of the brightest and most scientifically interesting comets of recent
    Message 1 of 153 , Jan 28, 2012
      Comet Lovejoy C/2011 W3

      Made it to 500! My "project completed" comet is, on one hand, one of the
      brightest and most scientifically interesting comets of recent years, and,
      on the other hand, one of the most difficult and challenging comets I have
      ever observed.

      Comet Lovejoy is a Kreutz sungrazer, the first such comet discovered from
      the ground in 41 years (although hundreds have been detected by orbiting
      coronagraphs aboard spacecraft, most notably SOHO). After passing through
      perihelion on December 16 it emerged into the southern hemisphere's morning
      sky during the last two weeks of 2011. From all accounts, Comet Lovejoy was
      a spectacular sight from the southern hemishere during that time, with a
      naked-eye tail in excess of 30 degrees long, and with several observers
      according it "Great Comet" status.

      The situation was very different from the northern hemisphere. I did try for
      the comet during daylight on several occasions as it was approaching and
      receding from perihelion, but apparently it wasn't quite bright enough to
      detect with the equipment I had. Afterwards, all I could do was view with
      envy the images from the southern hemisphere, and read accounts of how,
      after early January, it began fading, until by mid-month there was little
      left but a "ghostly" tail (still quite long) and essentially no coma.

      By the latter part of January the comet had traveled far enough north for me
      to attempt. On the evening of the 22nd, with the 41-cm telescope I seemed to
      detect an extremely pale and vague "something" with about the same surface
      brightness as the gegenschein, that nevertheless moved with the expected
      rate in the expected direction during the 1 1/2 hours that I followed it.
      After being clouded out the next two nights I tried again on the evening of
      the 25th, and once again saw this extremely pale and vague glow, and I was
      able to confirm it as being the comet by following it for two hours as it
      again moved with the expected rate and direction. On January 26.15, "m1" =
      12.0 (extinction corrected); 3' "coma;" I would take both of these values
      with the proverbial grain of salt, since I'm not sure what physical meaning
      the "magnitude" has in a situation like this, and the "coma" was so
      ill-defined that it was almost meaningless to attempt a size measurement; at
      times it seemed to be twice this size, or even larger.

      I am almost certainly finished with the comet, as the moon is now starting
      to wash out the evening sky, and I'm sure there will be nothing left to
      detect of it once the moon clears out. Since Comet Lovejoy may well be the
      first member of a "cluster" of Kreutz sungrazers that was predicted in a
      recent paper by Zdenek Sekanina and Paul Chodas, there may be more of these
      comets in the years to come, and hopefully at least one will pass through
      perihelion during the September/October timeframe, which will allow
      observations from the northern hemisphere as well.

      Description at http://www.earthriseinstitute.org/coms49.html#500

      Images and reports (including reports of outreach efforts) are welcome.


    • Alan Hale
      Hi everyone, First off, I would like to thank everyone for their kind comments and words of encouragement after I successfully added comet no. 500. (And
      Message 153 of 153 , Feb 5, 2012
        Hi everyone,

        First off, I would like to thank everyone for their kind comments and words
        of encouragement after I successfully added comet no. 500. (And special
        thanks to Terry Lovejoy for discovering it!) It has been an interesting
        ride, not only the past five years while I was actually pursuing
        "Countdown," but the entire 42 years since I spotted Comet Tago-Sato-Kosaka
        on that February evening way back when.

        Everyone's asking, "what's next?" For one thing, I'm continuing to observe
        as I always have, and I've already been looking for no. 501. (Don't have it
        yet, although I've already looked for four different comets that could have
        been it had I successfully detected them.) I don't foresee slowing down or
        stopping anytime soon, although there will probably come a point sometime
        when I no longer feel like trying to track down every single 14th-magnitude
        comet that comes along. At the end of the essay I wrote when I started
        "Countdown" (http://www.earthriseinstitute.org/comessay.html) I mentioned
        some comets that I hope to see in the future; to those I might add comets
        like PANSTARRS C/2011 L4 (it would be nice if we northerners could have a
        "Great Comet" for a change), and any additional incoming members of the
        Sekanina-Chodas "cluster" of Kreutz sungrazers (please, please, will at
        least one of these pass perihelion during September or October so we
        northerners can appreciate it, too?) While I don't expect it to get bright,
        it will be most interesting to follow 67P/Churyumov-Gerasimenko during its
        next return while it is being accompanied by Rosetta.

        For the time being, I will continue to update my update page
        (http://www.earthriseinstitute.org/comupdate.html) on an approximately
        weekly basis. I will certainly include new tally additions as they are
        added, although this will usually be done without announcement or fanfare.

        As for future programs:

        Most of you are probably aware, perhaps through my various "Countdown"
        announcements, that I underwent some significant upheavals in my personal
        life over the past few years, and among other things these have forced me to
        put any kind of Earthrise-related activities and programs on the back
        burner. However, those upheavals and changes are behind me now, and I am
        once again able to focus on developing some worthwhile educational and
        research programs.

        With that thought, yes, there will be a new comet-related observing program,
        and I am currently in the process of putting it together. Although there are
        still a number of details to be worked out, the primary focus will be on
        scientific observations of comets, and in fact some of you have already
        communicated some interesting thoughts to me along these lines, and I will
        likely be incorporating these into the program. Some of you have also
        privately communicated an interest in being part of such a program, and I
        can pretty much guarantee I will be taking you up on that, and meanwhile
        sometime in the not-too-distant future I will likely be issuing a general
        call for others who might be interested, and will also likely approach a few
        of you privately as well.

        I also should be acquiring some new equipment within the fairly near future,
        which should enable me to re-start my imaging program. I know I will never
        be able to match the quality of the work of some of the talented people on
        this list, but even so I would like to think I can take some images that are
        somewhat aesthetically pleasing as well as scientifically useful.

        So, I would just say, "watch this space!" I'm hopeful of announcing the new
        program in two to three months, but we'll see. In any event, may there
        continue to be comets that keep appearing for all of us to enjoy.


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