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C/2011 W3 (Lovejoy)

Orbit by Minor Planet Center

Image of comet Lovejoy on 2011 December 23
Copyright © 2011 by Vello Tabur (Michelago, New South Wales, Australia)

This image was acquired on December 23.7 (UT), using a Canon 400D DSLR camera with a 50mm lens.

Discovery

Terry Lovejoy (Thornlands, Queensland, Australia) discovered this comet in the course of his comet survey using a 20-cm Schmidt-Cassegrain telescope and a QHY9 CCD camera. On the morning of 2011 November 27, he acquired three images of about 200 different fields. After spending about two hours processing the images, he noticed a set made during November 27.73-27.75 (UT), which showed "a rapidly moving fuzzy object." Lovejoy was not certain what this was and made a note of "possible reflection" and continued examining the other images. The next night, he re-examined the images and noted that the "position, shape and motion didn't appear consistent with an optical reflection...." On November 29.7, Lovejoy acquired a series of images around the estimated position of the object and managed to "capture 6 images that showed a faint but definite fuzzy object near the expected position. Additionally the fuzzy object was consistent in both motion and appearance to the object found 2 mornings earlier." A request was made to "trusted observers," but all attempts on November 30 failed either because of bad weather or "insufficient limiting magnitude." Lovejoy said a communication from Michael Mattiazzo stated that the positions "were similar to that of a Kreutz sungrazer." Independent confirmation was finally made on December 1, when A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) managed to acquire four images of the comet using the 100-cm McLellan reflector and a CCD camera. Lovejoy made an report to the Central Bureau for Astronomical Telegrams and the comet was officially announced on December 2.


Image of comet Lovejoy on 2011 November 27
Copyright © 2011 by Terry Lovejoy (Thornlands, Queensland, Australia)

These are the three discovery images acquired by Lovejoy on the morning of 2011 November 27. The comet appears near the center and is very diffuse. It is moving toward the left, being over the top of a star in the middle picture.


Historical Highlights

  • The first parabolic orbit was calculated by G. V. Williams on 2011 December 2. He took 31 positions from the period spanning 2011 December 1-2 and determined the perihelion date as 2011 December 16.00. The perihelion distance was given as 0.0059 AU. This distance and the angular aspects of the orbit indicated this was a Kreutz sungrazer...the first such comet visible from Earth since 1970. The Minor Planet Center released a revised orbit on December 5 that showed only a slight variation in the orbit. The perihelion date was given as 2011 December 15.99, while the perihelion distance was 0.0056 AU. This was based on 40 positions from the period of December 1-4.

    The first elliptical orbit was published by Williams on December 11. Using 91 positions from the period of November 27 to December 8, Williams calculated a perihelion date of December 16.02, a perihelion distance of 0.0055, and a period of about 377 years. A revision was published by Williams on December 16. This extended the observational arc by two days and determined the perihelion date as December 16.01, the perihelion distance as 0.0056, and the period as about 680 years. K. Kinoshita published an elliptical orbit on December 17, which used 94 position from the period of November 27 to December 10. This gave the perihelion date as December 16.01 and the period as about 681 years.

  • Observations from around the Southern Hemisphere commenced on December 2, although the majority of these were acquired using various camera systems; however, there were still plenty of visual observers following the comet. Lovejoy saw the comet using his 32-cm reflector on December 3. He gave the magnitude as 11.6 and noted a moderately condensed coma 1' across. M. Goiato (Aracatuba, Brazil) saw the comet on December 4. Using his 22-cm reflector, he gave the magnitude as 10.7 and said the coma was 2' across. M. Mattiazzo (Castlemaine, Victoria, Australia) spotted the comet on December 5, using his 28-cm reflector. He estimated the magnitude as 11.2 and noted a moderately condensed coma 1' across.
  • In the days following the discovery, discussions on several comet blogs turned to the comet's survival probability. Among the very experienced comet observers, the opinion evolved that the comet was too small to survive perihelion and that the real question was, would it perish before or during perihelion. This assumption was based on the fact that the comet initially appeared similar to the more than a thousand pygmy sungrazers that had been observed by the SOHO spacecraft during the previous 16 years...none of which survived perihelion. Interestingly, the comet started to dramatically brighten a couple of days prior to passing perihelion, prompting R. McNaught (Siding Spring Observatory, New South Wales, Australia) to suggest this could be a comet that is intermediate between the pygmies and the bright visual sungrazers seen from Earth in the past.
  • When the comet was closest to the sun, an armada of spacecraft designed to observe the sun and its surroundings, provided movies of the comet's approach and re-emergence.
  • Movie acquired by the Solar Terrestrial Relations Observatory (STEREO)
    2011 December 12-14 (during comet approach to Sun)

    Movie of comet Lovejoy during 2011 December 12-14
    Copyright © 2011 by NASA/STEREO/NRL

    Movie acquired by the Solar Dynamics Observatory (SDO)
    2011 December 15-16 (during comet approach to Sun)

    Movie of comet Lovejoy during 2011 December 12-14
    Copyright © 2011 by NASA/SDO

    Movie acquired by the Solar Terrestrial Relations Observatory (STEREO)
    using the EUVI instrument at the 171-angstrom wavelength
    2011 December 16 (during comet emergence from behind Sun)

    Movie of comet Lovejoy during 2011 December 16
    Copyright © 2011 by NASA/STEREO/NRL


    Earliest Post-Perihelion observations from Earth


  • The very first observation made from Earth following perihelion came from Rick Baldridge and Brian Day (Foothill College Observatory, Los Altos Hills, California) on December 16.83. Using a 41-cm Schmidt-Cassegrain telescope with a nearly 8-cm off-axis mask, Baldridge used the dome shutter to block the sun, focused the telescope on Venus, and then moved the telescope to the comet's predicted position. After a few moments, he saw a "very star-like nucleus with a faint but obvious fan shaped glow streaming away from it. The fan was maybe 20 arc-seconds long. A very rough guess was the nucleus was magnitude -1, based on my impression of the appearance of Mercury years ago at a similar solar elongation." Baldridge called Day, who was parking his car, and Day soon entered the observatory for a look. Upon looking through the telescope and letting his eyes adjust, Day exclaimed, "DAMN! There is is!"
  • A few hours after the visual sighting, the comet's discoverer, Terry Lovejoy, photographed the comet from his home in Australia on December 17.05. Using the same 20-cm reflector he used to discover the comet and a Canon 350D digital camera, Lovejoy reduced the opening to 5-cm and attached a hood ("to reduce sunlight into the scope") and acquired 14 1/320-second exposures. A comparison with Venus (magnitude -3.9) enabled Lovejoy to estimate the magnitude as -1.2. He added that the coma was about 0.5 arc minutes across, while there was some hint of tail. Lovejoy acquired eight 1/1250-second expsoures with the same equipment on December 17.85 (still daylight). He estimated the magnitude as -0.8. The coma and tail were unchanged from earlier in the day.
  • Image acquired in daylight by T. Lovejoy on 2011 December 17.05
    Image of comet Lovejoy on 2011 December 17
    Copyright © 2011 by Terry Lovejoy (Thornlands, Queensland, Australia)

  • Another exceptional set of observations was made by Vincent Jacques (Breil-sur-Roya, France). During the period of December 17.38 to 17.54, he said the comet was easily visible in daylight using an 8-cm refractor. In addition, using the same telescope, he acquired several images using an near infrared filter and a DMK21 CCD camera.
  • Movie of comet Lovejoy during 2011 December 17
    Copyright © 2011 by Vincent Jacques (Breil-sur-Roya, France)

    Movie of comet Lovejoy during 2011 December 17
    Copyright © 2011 by Vincent Jacques (Breil-sur-Roya, France)

    Even More Post-Perihelion observations


  • Additional visual observations were made as the comet continued to move away from the sun. Alexandre Amorim (Florianopolis, Brazil) spotted the comet using 10x50 binoculars on December 17. He estimated the magnitude as -2.9 and said the coma was very strongly condensed and about 1 arc minute across. He noted the tail extended 0.2 degrees in PA 240. The comet was then 4 degrees above the horizon, while the sun was 0.9 degrees below the horizon. William Souza (Sao Paulo, Brazil) saw the comet on December 18 using 11x80 binoculars. He gave the magnitude as -1.0 and said the coma was 1' across. The tail extended 5' in PA 240 degrees. Noel Munford and Ian Cooper (Sluggish Creek Observatory, Glen Oroua, Manawatu, New Zealand) were seemingly headed for an unsuccessful search for this comet on the morning of December 19, because of clouds over the eastern horizon; however, using 10x50 binoculars, they finally spotted the tail extending 30' to 40' above the cloud tops toward a position angle of 120 degrees. Later the same day, the comet was again seen by Souza. Using his 11x80 binoculars, he gave the magnitude as -0.5 and noted the tail extended 0.3 degrees in PA 240 degrees.
  • Sudden Transformation


  • Late on December 20 (UT) images began revealing that the comet might be undergoing a dramatic change. J. Cerny released images that had been acquired by the FRAM telescope around December 20.86, which showed the nucleus had apparently become bar-shaped and was accompanied by a bright tail ray, as shown below:
  • Movie of comet Lovejoy during 2011 December 20
    Copyright © 2011 by Jakob Cerny


  • Shortly after this image was posted on the comets-ml discussion group, Alan Watson brought attention to a movie that had been put together using images from the STEREO HI1A spacecraft that were taken during December 18 and 19. These seemed to show the head of the comet decreasing in size and a "dust tail wedge...getting longer and broader." This movie is shows below:
  • Movie of comet Lovejoy during 2011 December 18-19
    Copyright © 2011 by NASA/STEREO/NRL

    More Visual Observations


  • Marco Goiato (Aracatuba, Brazil) saw the comet with 20x100 binoculars on the 20th and gave the magnitude as 1.2. The coma was very strongly condensed. On the 21st, the comet was independently seen by Reginaldo Nazar (Agudos do Sul, Parana, Brazil) and Jose Guilherme de Souza Aguiar (Campinas, Brazil). They gave the magnitude as 2.0 and 2.1, respectively. Nazar noted the coemt was moderately condensed and 10' across, while the tail extended 15 degrees. On the 22nd, Chris Wyatt (Bendemeer, New South Wales, Australia) saw the comet using 7x50 binoculars and said the tail was about 14 degrees long.David Herald (Murrumbateman, Australia) first saw the comet about a half hour before its head was supposed to rise. He noted 10 degrees of the tail was visible, with a surface brightness "similar to the Magellanic clouds--even though they are higher in the sky."

    A number of observations were reported for December 26. Vello Tabur (Boorawa, New South Wales, Australia) said the comet had faded significantly, but was still an easy naked-eye object. He said "the tail was fainter than the nearby Milky Way and is now only slighlty brighter than the SMC [Small Magellanic Cloud]."David Seargent (Cowra, New South Wales, Australia) said the magnitude of the comet's head was 5.3, while the tail was about 37 degrees long. John Drummond (Gisborne, New Zealand) photographed the comet and said the tail was 38 degrees long. He added that the tail exhibited a "faint, greenish hue starting at the bottom and going straight up to nearly the top."

    Andrew Pearce (Lockington, Victoria, Australia) observed the comet on December 28. He said the tail was 30 degrees long and noted, "What is most striking about it is it's extreme straightness." He added that the head was "virtually non existent."

  • Additional Images

    Images: 2011 November 27 to December 15


    Images: 2011 December 18-19


    Image of comet Lovejoy on 2011 December 20
    Copyright © 2011 by Colin Legg (Mandurah Estuary, Western Australia, Australia)

    Colin shot this image of the comet on December 20.82, 2011 (UT) using a Canon 5D Mark 2 DSLR camera and a 73mm lens. This was a 12-second exposure.


    Images: 2011 December 21


    Image of comet Lovejoy on 2011 December 22
    Copyright © 2011 by Rodney Austin (New Plymouth, New Zealand)

    This image was acquired on December 22.63.This was a 30-second exposure using a Canon Kiss DSLR and a 43mm lens.


    Image of comet Lovejoy on 2011 December 23
    Copyright © 2011 by Gordon Garradd (Loomberah, New South Wales, Australia)


    Image of comet Lovejoy on 2011 December 23
    Copyright © 2011 by Rob Kaufman (Bright, Victoria, Australia)


    Image of comet Lovejoy on 2011 December 23
    Copyright © 2011 by Andrew Wall (Dublin, South Australia, Australia)

    Andrew obtained this widefield image showing the comet on December 23. He was using a Canon 17-40mm lens.


    Image of comet Lovejoy on 2011 December 23
    Copyright © 2011 by Robert McNaught (Siding Spring Observatory, New South Wales, Australia)

    Rob obtained this wide-angle image showing the comet, the Milky Way, and the dome of the Anglo-Australian Telescope on December 23.72 (UT). This is a 240-second exposure acquired using a Canon 5D and a 24mm lens.


    Image of comet Lovejoy on 2011 December 25
    Copyright © 2011 by Colin Legg (Esperance, Western Australia, Australia)

    Colin shot this image of the comet on December 25.78, 2011 (UT) using a Canon 5D Mark 2 DSLR camera and a 14mm lens. This was a 25-second exposure.


    Image of comet Lovejoy on 2011 December 26
    Copyright © 2011 by Vello Tabur (Boorowa, New South Wales, Australia)

    Tabur acquired this image on December 26.7 (UT), using a Canon 400D DSLR camera with a 50mm lens. This was a 153-second exposure.


    Image of comet Lovejoy on 2011 December 29
    Copyright © 2011 by Gordon Garradd (Loomberah, New South Wales, Australia)

    Garradd acquired this image on December 29, 2011, showing the comet and the Milky Way.


    Image of comet Lovejoy on 2012 January 4
    Copyright © 2012 by Michael Mattiazzo (Castlemaine, Victoria, Australia)

    M. Mattiazzo acquired this image on 2012 January 4.69, using a Canon 300D DSLR camera with an 18mm lens. Twelve 30-second exposures were stacked to produce this image.


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