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Countdown to 500 Comets: no. 487

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  • Alan Hale
    Comet Elenin C/2010 X1 This would certainly have to be considered among the more eagerly-awaited comets of recent years. It was discovered last December by
    Message 1 of 153 , Jun 9 10:08 AM
      Comet Elenin C/2010 X1

      This would certainly have to be considered among the more eagerly-awaited
      comets of recent years. It was discovered last December by Russian
      astronomer Leonid Elenin using a remote-controlled telescope in New Mexico;
      at that time it was a dim and distant object but has been steadily
      approaching the sun and Earth ever since. It was at opposition in mid-March
      and I successfully imaged it as an object of magnitude 15 1/2 to 16 later
      that month. I also began visual attempts around that time, but the comet
      remained elusive for the next two months. Finally, I picked up a very faint,
      diffuse, and "soft" suspect on the evening of May 23, and was able to verify
      this as being the comet by observations over several subsequent nights.
      (Because the comet was at its stationary point at that time there was hardly
      any motion from night to night.) On May 24.19, m1=14.4, 0.7' coma; on May
      31.18, m1=14.2, 1.1' coma.

      The comet is traveling in a remarkably low-inclination orbit (inclination
      1.8 degrees). It remains in the evening sky up through perihelion passage on
      September 10 (at which time its solar elongation will be 26 degrees),
      however after that it passes almost directly between the earth and the sun
      in late September and then rapidly emerges into the morning sky during the
      first week of October. It travels rapidly towards the west-northwest and
      passes 0.23 AU from Earth on October 16; by early November it enters Taurus
      and is at opposition shortly after the middle of that month before crossing
      the northern section of the Pleiades star cluster on November 23. The comet
      enters Aries at the end of November and remains there for the next two

      Comet Elenin possesses the potential to be a relatively bright, perhaps even
      conspicuous, naked-eye object. However, it is currently running quite a bit
      fainter than the original expectations for this time, and furthermore
      calculations have now shown that it is making its first visit into the inner
      solar system from the Oort Cloud; such comets tend to under-perform as they
      pass through perihelion. A cautiously optimistic projection based upon its
      present brightness suggests a peak brightness of 5th or 6th magnitude during
      September and October, although it could well be one or two or more
      magnitudes brighter, or fainter, than this. There is a possibility of a
      fairly strong brightness enhancement due to forward scattering of sunlight
      when the comet passes between the earth and the sun in late September,
      however this will probably be quite brief and, more importantly, the comet's
      elongation from the sun will be very small. (On the other hand, it should
      make for a spectacular show in the LASCO coronagraphs aboard SOHO.)

      Description at http://www.earthriseinstitute.org/coms48.html#487

      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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