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29P/Schwassmann-Wachmann 1

Past, Present, and Future Orbits by Kazuo Kinoshita

Spitzer Space Telescope image of 29P exposed on 2003 November 24

This image was obtained by the Spitzer Space Telescope, which is an infrared telescope launched in August of 2003. The image was obtained in the 24 micron range by the multiband imaging photometer. It "shows thermal infrared emission from the dusty coma and tail of the comet." The image measures 24.3 arc minutes wide and 15.9 arc minutes tall. The observers were Dale Cruikshank, Principal Investigator (NASA Ames Research Center), John Stansberry, Principal Investigator (University of Arizona), William Reach (SSC/Caltech), Yanga Fernandez (University of Hawaii), Michael Werner (JPL/Caltech), George Rieke (University of Arizona), Vikki Meadows (JPL & SSC/Caltech)


     Arnold Schwassmann and Arno Arthur Wachmann (Hamburg Observatory, Bergedorf, Germany) discovered this comet on photographs exposed on November 15, 1927. Then near magnitude 13.5, the comet proceeded to fade very rapidly during the next few days with estimates of 15 on November 28 and 16 by December 1.
     In 1931 prediscovery images were found by Karl Reinmuth on photographic plates exposed on 1902 March 4 and 5. The comet was then near magnitude 12.

Historical Highlights

  • The comet is unique in that it experiences one or more outbursts in brightness nearly every year. The comet's normal brightness is near 17 at perihelion and 19 at aphelion, but these outbursts can cause it to reach 13. On rare occasions it has even reached magnitude 10.
  • The comet's orbit is nearly circular and lies just outside the orbit of Jupiter. It has been stabilizing since its discovery, with the initial eccentricity being 0.15 and the present being 0.04. During the same time the orbital period has declined from 16.0 years to 14.9 years.
  • The comet was last at perihelion on 1989 October 26 (5.7718 AU). It underwent a stronger than normal brightness outburst during 1996 February, at which time it reached magnitude 11.5. Observers continued to provide magnitude estimates of 11 to 12 well into April, but the comet finally began fading during the latter part of that month. The comet's "normal" brightness for this part of its orbit is around 19.
  • Close approaches to planets: The comet experienced two minor approaches to Jupiter during the 20th century. There will be one approach to Jupiter during the 21st century. (From the orbital work of Kazuo Kinoshita)
    • 1.95 AU from Jupiter on 1930 July 11
      • increased perihelion distance from 5.47 AU to 5.52 AU
      • decreased orbital period from 16.44 to 16.14 years
    • 1.00 AU from Jupiter on 1974 May 8
      • increased perihelion distance from 5.45 AU to 5.77 AU
      • decreased orbital period from 14.96 to 14.85 years
    • 0.90 AU from Jupiter on 2037 October 11
      • increased perihelion distance from 5.71 AU to 5.87 AU
      • increased orbital period from 14.37 to 15.87 years

    Additional Images

    Toru Yusa image of 29P exposed on 1996 March 28
    Copyright © 1996 by Toru Yusa (Kogota, Japan)

    This image was taken on 1996 March 28.64, using a 0.20-m f/5.9 Meade LX200 Schmidt-Cassegrain and an SBIG ST-6 CCD camera.

    H. Mikuz images of 29P exposed early in 1996
    Copyright © 1997 by Herman Mikuz (Crni Vrh Observatory, Slovenia)

    This series of images was obtained early in 1996 using a 36-cm, f/6.8 S-C telescope and CCD. Each image was a 300-second exposure. The left and center images, obtained on January 18 and February 24, respectively, show an outburst in progress. The right-hand image was obtained on March 10 and shows the outburst subsiding.

    Akimasa Nakamura images of 29P exposed during April and May of 1997
    Copyright © 1997 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)

    These three images were taken by A. Nakamura during an outburst during April of 1997. The image of April 12.60 shows the outburst in progress. That of April 28.59 shows the comet near maximum brightness. The image of May 9.55 shows the outburst subsiding. The images were obtained with a 0.60-m f/6 Ritchey-Chretien telescope and a CCD camera.

    Gerald Rhemann and Michael Jäger image of 29P exposed on 2003 July 26.02
    Copyright © 2003 by Gerald Rhemann and Michael Jäger (Austria)

    This image was obtained by G. Rhemann and M. Jäger on 2003 July 26.025. It shows the comet undergoing one of its fairly frequent outbursts in brightness. Interestingly, the image also shows a tail, which is a feature rarely seen for this comet. Rhemann and Jäger estimated the comet's magnitude as 12 and the coma diameter as 4 arc minutes. The tail extends 12 arc minutes toward PA 215°. The image was obtained with a 14-inch reflector and a Starlight SXV-H9 CCD camera. Three 210-second exposures were combined.

    R. Ligustri image of 29P exposed on 2003 September 17
    Copyright © 2003 by R. Ligustri (Talmassons, Italy)

    This image was obtained on 2003 September 17.81 UT with the 350/1750 reflector and an SBIG ST9E CCD camera. Ten 240-second exposures were combined. The image covers a field measuring 16' by 16'. North is toward the top, while east is to the left.

    G. Masi and F. Mallia image of 29P exposed on 2004 June 23
    Copyright © 2004 by Gianluca Masi and Franco Mallia (Italy)

    This image was obtained on 2004 June 23.36 UT with the 14-inch SoTIe telescope (Las Campanas, Chile). They stacked three 60-second images, which revealed a coma 50" across and a jet extending 20" toward PA 45°. The field of view is 6.5' by 6.5'.