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96P/Machholz 1

Past, Present, and Future Orbits by Kazuo Kinoshita

SOHO image of 96P exposed on 2002 January 6 to 9

Copyright © 2002 by the Solar and Heliospheric Observatory (SOHO)

Several images were obtained of this comet by SOHO during 2002 January 6 to 9. The images were acquired by the Large Angle and Spectrometric COronagraph (LASCO) C3 coronograph. Three images have been overlayed by the webmaster and the times in Universal Time have been put next to each comet image. As can be seen, the comet was moving from the bottom (south) toward the top (north).

Discovery

     Don E. Machholz (Loma Prieta, California, USA) discovered this comet on 1986 May 12.45. He was then using 29x130 binoculars. Machholz determined the total magnitude as 11.0 and said the object was diffuse without condensation. No tail was reported. Charles Morris (near Mt. Wilson, California, USA) confirmed the comet on May 13 and determined the magnitude as 9.7 with his 0.25-m reflector. He was observing with Alan Hale, who determined the brightness as 9.8 with his 0.20-m reflector.

Historical Highlights

  • B. G. Marsden (Central Bureau for Astronomical Telegrams) computed and published the first orbit for this comet on IAUC 4217 (1986 May 15). It was a parabolic orbit with a perihelion date of 1986 April 24, a perihelion distance of 0.14 AU, and an inclination of 76 degrees. By June enough observations had been collected to enable a solution more precise than parabolic. Marsden published an orbit by S. Nakano on IAUC 4223 (1986 June 3), which indicated the orbit was not just elliptical, but of short period. Nakano's orbit indicated the perihelion date was 1986 April 23.5, the perihelion distance was 0.1268 AU, the inclination was 60 degrees, and the orbital period was 5.34 years. Further calculations by Marsden indicated the perihelion date might still be uncertain by a month or two, and that minimum separations from Jupiter might have occurred in 1972 (1.3 AU) and 1984 (1.6 AU). Improvements in the orbit continued to be made and the comet next passed perihelion on 1991 July 21. The predictions for that return required a correction of only -0.03 day.
  • Apparition of 1986: The comet slowly faded after discovery with the decreasing distance from Earth somewhat countering the increasing distance from the sun. By the end of May magnitude estimates were generally around 11. The comet continued to show only slight condensation within the 2 to 3 arc minutes across coma. Photographs revealed a short tail extending about 4 arc minutes around mid-May, as well as an anti-tail extending up to 2 arc minutes from the nucleus. The comet passed only 0.4 AU from Earth during the first days of June and fading became more rapid thereafter.
  • 1988-1990: With such a short-period orbit, astronomers realised the relatively small aphelion distance might enable the comet to be seen completely around its orbit. Observations were obtained in 1988, 1989, and 1990, so that the comet was actually seen near aphelion, as well as early in its return towards its next perihelion.
  • Apparition of 1991: A. C. Gilmore and P. M. Kilmartin (Mount John University Observatory) photographed the comet about three weeks prior to the next perihelion. Their photographs with the 0.6-m reflector on July 3, 4, and 5 revealed what may have been a sharp increase in the comet's activity. The photos of the 3rd and 4th revealed a nucleus of magnitude 16, while that of the 5th revealed a 14th magnitude nucleus and a faint, narrow tail extending 30 arc seconds towards the south-southwest. The comet was not seen by amateur astronomers until after perihelion. During the last day of July and first days of August, magnitude estimates were generally in the range of 8 to 9. The closest distance from Earth was 0.94 AU, which came on August 7. The comet faded rapidly thereafter.
  • Apparition of 1996: This was not a favorable return. Early attempts to try and detect the comet as it approached perihelion were made by A. Pearce (Australia) on August 24 and September 21. It was decided that the comet must have been fainter than magnitude 12.5 on the first date and fainter than 11 on the second. The comet was due at perihelion on October 15. Interestingly, the SOHO satellite photographed the comet on October 13 to 16 (see the image below). Dr. O. Christopher St. Cyr said the satellite's images revealed the comet was then about magnitude 4.5 with a tail about 2 degrees long.
  • Close approaches to planets: The comet experienced two close approaches to Earth during the last half of the 20th century. It makes two close approaches to Earth and one close approach to Jupiter during the first half of the 21st century. (From the orbital work of Kazuo Kinoshita)
    • 0.46 AU from Earth on 1965 June 3
    • 0.40 AU from Earth on 1986 June 6
    • 0.87 AU from Jupiter on 2008 May 13
      • decreased perihelion distance from 0.125 AU to 0.124 AU
      • increased orbital period from 5.24 to 5.28 years
    • 0.32 AU from Earth on 2028 June 16
    • 0.36 AU from Earth on 2049 June 24

    Additional Images

    Michael Jäger obtained this image of Machholz 1 on 1986 June 26 during an outburst in brightness
    Copyright © 2002 by Michael Jäger (Austria)

    This image was obtained by Michael Jäger on 1986 June 26.93. The image was a 5-minute exposure obtained with a Schmidt-Cassegrain 200/300 and TP hyp film. The comet was located about 1.54 AU from the sun and was about magnitude 11.0 because of an outburst in brightness.


    SOHO image of 96P exposed on 1996 October 14 and 15

    Copyright © 1996 by the Solar and Heliospheric Observatory (SOHO)

    Several images were obtained of this comet by SOHO during 1996 October 14 and 15. The images were acquired by the Large Angle and Spectrometric COronagraph (LASCO) C3 coronograph. Three images have been overlayed by the webmaster and the times in Universal Time have been put next to each comet image. As can be seen, the comet was moving from the bottom (south) toward the top (north). The tail divides in the later image, revealing a curved dust tail and a straight, narrow gas tail.


    Michael Jäger obtained this image of Machholz 1 on 2002 January 22 when 20 from the sun
    Copyright © 2002 by Michael Jäger (Austria)

    This image was obtained by Michael Jäger on 2002 January 22.25. The image was a 1.5-minute exposure obtained with a 10-inch Schmidt camera and Kodak TP2415 hyp film. The comet was located about 20° from the sun and was about magnitude 8.0.

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