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81P/Wild 2

Past, Present, and Future Orbits by Kazuo Kinoshita

Stardust image of 81P exposed on 2004 January 2
Copyright © 2004 by Jet Propulsion Laboratory

These images of the nucleus of periodic comet Wild 2 were taken by the Stardust space probe on 2004 January 2. They were shot within minutes of the closest approach to the nucleus. Details released on the right-hand image indicate it is a 10-millisecond exposure.


     Paul Wild (Astronomical Institute of Berne, Switzerland) discovered this comet on photos exposed by him on 1978 January 6 and 8. He said the comet was between magnitude 13.5 and 14, with a marked condensation. The discovery was announced on IAU Circular 3166 (1978 January 26). Meanwhile, Wild had photographed the comet again on January 25. This observation allowed Brian G. Marsden to determine the comet moved in a short-period orbit of about 6.15 years.

Historical Highlights

  • Although Marsden had indicated in 1978 that this comet had passed close to Jupiter in 1974, it was S. Nakano who uncovered more of the details in 1979. He said the comet had passed only 0.2 AU from Jupiter in 1974. This close approach drastically decreased the orbital period from nearly 40 years to only 6.17 years, while the perihelion distance was decreased from 4.9 AU to only 1.49 AU.
  • The comet was next recovered on 1983 September 18.44 and has been seen nearly every year up to the present time, as the orbit barely takes it out of range of present-day telescopes when it is nearing aphelion. Following the 1983 recovery, observatories managed to acquire observations every month through 1984 April. Additional observations were obtained during the period of 1985 April to September and 1986 September. After a break in 1987 (the comet's aphelion), observations were acquired in 1988, 1989, 1990, 1991, and 1992 as the comet approached and passed its third observed perihelion passage.
    [Perihelion Date=1997 May 6.63; Period=6.39 years]
         The comet's next perihelion date was 1997 May 6. The comet was recovered on 1995 January 2 and was kept under observation until 1998 September 16. It was kept under observation every month from 1996 August through 1997 August. During the first months of 1997 the total magnitude peaked near 9.

    [Perihelion Date=2003 September 25.94; Period=6.40 years]
         This comet was picked up at during September of 2002 at a magnitude between 19 and 20. It brightened rapidly and by 2003 January 1 it was already reported at between magnitude 15 and 16. The comet was followed into May, when observers indicated it had reached magnitude 14, if not slightly brighter. The comet was then lost in the sun's glare for the remainder of the year.
         This comet was visited by STARDUST, NASA's comet sample return mission, on 2004 January 2. Stardust flew through the coma on the sunward side of the nucleus and missed the nucleus by just 240 kilometers. STARDUST has a panel containing a material called aerogel, which collected samples of the comet's dust. These samples will be returned to Earth on 2006 January 15.

  • Close approaches to planets: This comet made 1 close approach to Earth, 1 close approach to Mars, and 1 close approach to Jupiter during the 20th century. It makes 3 close approaches to Earth during the first half of the 21st century. (From the orbital work of Kazuo Kinoshita)
    • 0.0061 AU from Jupiter on 1974 September 9
      • decreased perihelion distance from 4.95 AU to 1.49 AU
      • decreased orbital period from 43.17 to 6.17 years
    • 0.07 AU from Mars on 1978 August 5
    • 0.85 AU from Earth on 1997 February 12
    • 0.67 AU from Earth on 2010 April 5
    • 0.92 AU from Earth on 2029 February 8
    • 0.65 AU from Earth on 2042 April 5

    Additional Images

    Tichy and Moravec image of 81P exposed on 1997 January 15
    Copyright © 1997 by M. Tichy and Z. Moravec (Klet' Observatory, Czech Republic)

    The image of comet 81P/Wild 2 was taken on 1997 January 15.936 UT with 0.57-m f/5.2 reflector + CCD camera SBIG ST-8 of Klet' Observatory and is 60 seconds exposure. The field of view is 16 to 10 arcminutes with north to the top and west to the right.

    G. Masi image of 81P exposed on 1997 March 3
    Copyright © 1997 by Gianluca Masi (Ceccano, Italy)

    This image of comet Wild 2 was taken by G. Masi on 1997 March 3 at 18:57 UT. It was a 12-minute exposure obtained with a 15-cm f/5 reflector and an SBIG ST-7 CCD.

    Michael Brown image of 81P exposed on 1997 April 1
    Copyright © 1997 by Michael Brown (University of Melbourne)

    Michael Brown obtained this image using the 40-inch telescope at Siding Spring Observatory on 1997 April 1. It was actually shot through clouds.

    B. Wallis image of 81P exposed on 1997 April 7
    Copyright © 1997 by Brad D. Wallis (California, USA)

    This image of comet 81P was taken on 1997 April 7.27 UT with a 0.32-m f/5.9 Ritchey telescope, an SBIG ST-7 CCD camera, and a minus-IR filter. The image was composed of eleven 5-minute exposures.

    Masayuki Suzuki image of 81P exposed on 1997 May 18
    Copyright © 1997 by Masayuki Suzuki (Japan)

    This image was taken on 1997 May 18, using a 0.20-m f/10 telescope and a CCD camera. The image is a 60-second exposure.

    D. Higgins image of 81P exposed on 2003 January 11
    Copyright © 2003 by David Higgins (Hunters Hill Observatory, Canberra, Australia)

    This image was taken on 2003 January 11.92, using a 0.25-m SCT f/5 and an SX MX516 ccd camera. The image was composed of thirty 30-second exposures. The coma was 20.6 arc seconds across, while the tail extended 22.4 arc seconds toward PA 315°. The image was originally white with black stars and the webmaster reversed this to better represent the appearance of the comet.