Comet PANSTARRS Grows Fan-tastic Tail

Italian amateur astronomer Lorenzo Comolli captured beautiful symmetric rays called synchronic bands in the dust tail of Comet C/2011 L4 PANSTARRS on March 21, 2013 through his 5.5-inch refracting telescope. Credit: Lorenzo Comolli

I know. You’re probably got PANSTARRS fatigue. Still, I can’t help but direct your eyes once again to yet another wonderful photograph, this one made by Italian amateur astronomer Lorenzo Comolli. Like many of us, he lives in a light polluted area and must escape to find darker skies. For Lorenzo that means a trip to the Alps or Apennines.

Lorenzo with the scope he used to photograph the comet. Credit: Lorenzo Comolli

His spectacular image was made using a 5.5-inch (140mm) wide-field refractor, a sensitive CCD camera and seven images. Each exposure lasted 2 minutes during which time he carefully guided the telescope to follow the comet’s motion across the star field. Lorenzo then stacked all seven images one atop the other in an photo program like Photoshop to create a single, high resolution photo.

Astrophotographers prefer stacking a series of short-exposures instead of making one long exposure because it reduces noise (graininess) and the effects of light pollution. A 14-minute time exposure picks up more unwanted light than a 2-minute one.

Lorenzo added this information to his photo of PANSTARRS. The main tail is composed of very tiny dust particles; the short tail to the left, which tracks along the comet’s orbital path, is formed from the largest, heaviest dust bits. Credit: Lorenzo Comolli

Studying the picture we’re struck by the fan-like spread of multiple plumes of dust released by the comet as the heat of the sun vaporizes dust-laden ices. Cometary dust particles are extremely small, ranging in size from less than a micron (equal to one-thousandth of a millimeter) to 1/100 of a millimeter. For comparison, particles in wood smoke fall in the same range. Sunlight pressure physically pushes these tiny motes back to form the tail.

The real eye-catchers are the synchronic bands. Our best model points to their formation from individual fragments or chunks that break up once they’re released from the comet. As each new fragment crumbles into fine dust, it’s raked into a fresh by sunlight. I think you would agree the end result of such a simple process is breathtaking.

Comolli’s picture also records a dim tail made of sodium atoms, possibly released by collisions between dust grains flying off the comet’s nucleus, and a second dust tail of larger particles trailing behind the comet as it moves along its orbit around the sun. For more of Lorenzo’s images of Comet PANSTARRS, click HERE.

I’ve labeled the different parts of Comet PANSTARRS tail using information from Uwe Pilz on dust particles sizes. Cigarette smoke is 0.01 to 1 micron in size, a level or two smaller what we see for dust in comets. Credit: Lorenzo Comelli

Uwe Pilz of Leipzig, Germany has created a wonderful series of simulations of PANSTARRS’ tail that reveal how dust particles are sorted according to size across the comet’s multiple tails.

I’ve used his information to help you see what’s where in Lorenzo’s photo. Again for reference, a typical bacterium is between 0.2 and 3 microns across (same  as fine comet dust!), a human red blood cell 5 microns and a human hair is about 75 microns but varies by hair type.

While most of us will never see such such riches through our telescopes and binoculars, we can appreciate this hidden side side of PANSTARRS that superb amateur photography can reveal.

12 Responses

  1. Wayne Hawk

    Aloha Astro Bob!

    In my very humble opinion, I could NEVER get fatigued from information on any comet that is within viewing range (by amateur astronomers or ordinary people). Comets have been one of the biggest (if not tied for #1) mysteries of human beings ever since the first “person” looked up and saw one.

    Even with all the technology we have today and all we have learned about comets, there is so much we really don’t know about them that I doubt we will ever satisfy our curiosity. What we think of as “facts” today may very well be tomorrow’s false theories. As long as we keep seeking answers to all those “objects” that are constantly moving around “out there”, who knows what new “truths” will be discovered some day?

    This was a fascinating read and I can’t imagine how much money Lorenzo Comolli must have invested in his “photo-telescopic” setup, however, when a photograph is captured/assembled such as this one, I’m sure he feels it was all well worth it!

    Mahalo Bob!

    Aloha For Now!

  2. Brock

    Hi Bob,
    I love your articles and I’ve used your references on many occasions to star gaze. Could you please give a current update on the best time of day and location in the sky for us Minnesotans to see the comet PANSTARRS? Thanks much…


  3. Edward M. Boll

    It has now been 5 days since I have seen Panstaars. If it is clear I will be out tonight despite the fact that my alarm is set for work at 3 AM. At least that is not every day. Some including John Bortle are being cautious about ISON. It seems to be lagging for the last couple weeks. It may not reach magnitude -20, but I am still planning for a hopeful great show. Perhaps the tail may be the best part of it.

    1. astrobob

      Good luck tonight. I have to teach this evening so I won’t see it but looking forward to Thursday and no moon. -20 seems very, very optimistic, don’t you think?

  4. Stephen Atkinson

    Wouldn’t “individual fragments or chunks that break up once they’re released from the comet” be quite a random process, which wouldn’t give rise to such regular banding? My first thought is that it is some process tied to rotation of the nucleus – periodic differential heating and/or jetting.

    1. astrobob

      Hi Stephen,
      I agree with you and even recall reading that explanation a long time back, however I couldn’t find my old reference (or a new one) when I was writing the piece, so I held back. I’m picturing a continuously-active jet on a spinning nucleus. This did in fact happen with Comet Hale-Bopp, which resulted in multiple shells or halos around the false nucleus – a striking sight in the telescope. Comet PANSTARRS doesn’t appear to have any of these features.

  5. Kjell Olauson

    Hi Bob! Great pictures of PANSTARRS. Looking forward to a wide field image April 3rd or 4th when PANSTARRS and the Andromeda galaxy are separated by merely 2 or 3°.

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