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28P/Neujmin 1

Past, Present, and Future Orbits by Kazuo Kinoshita

E. E. Barnard drawing of 28P obtained on 1913 September 10
Copyright © 1913 Astronomische Nachrichten

This drawing was made by E. E. Barnard (Yerkes Observatory, Wisconsin, USA) on 1913 September 10.30, while viewing the comet with the 40-inch refractor. He at first thought the star in the center of the drawing was involved in the north preceding side of the comet's coma, but after a few minutes he realized the "star" was actually the comet's nucleus. This is the reason the comet was originally announced as a minor planet. South is up in the image and the diameter of the field is 5.5 arc minutes.


     G. N. Neujmin (Simeis Observatory, Crimea, Ukraine) discovered this object on a photograph exposed on 1913 September 3.98, during a routine search for minor planets. The object was stellar and of magnitude 10.0. It was announced by Neujmin as a new minor planet. Kudrewisch (Pulkovo Observatory, Saint Petersburg, Russia) photographically confirmed the new object on September 5.91 and gave the magnitude as 10.8. On September 7, J. O. Backlund (Pulkovo Observatory) announced that Neujmin's minor planet was actually a comet, while K. Graff (Hamburg Observatory, Bergedorf, Germany) came to the same conclusion when he detected a short tail on September 7.10.

Historical Highlights

  • The Orbit: The first parabolic orbits were based on three positions obtained on September 7 and 8. C. W. L. M. Ebell determined the perihelion date as 1913 July 23.04, while S. Einarsson and S. B. Nicholson determined it as 1913 October 3.88. Based on the orbit of Einarsson and Nicholson, A. O. Leuschner noted that a parabola was unsatisfactory and that a period of 17.44 years fit best. Elliptical orbits were calculated shortly thereafter with periods ranging from 9 to 25 years. The period was eventually established as 17.76 years.
  • Apparition of 1913 (discovery): At the time of discovery, this comet was about two weeks passed perihelion and less than two days passed its closest distance from Earth. Many observers were then estimating the magnitude as between 11 and 11.5. Many reported the comet as completely stellar in appearance, while some noted a faint trace of nebulosity toward the southeast side of the nucleus. Although the comet faded during the days and weeks that followed, T. Banachiewicz (Engelhardt Observatory, Kasan, Russia), Graff, and G. van Biesbroeck (Uccle, Belgium) noted some variations in the brightness of the nucleus. The comet was last detected on a photographic plate exposed by R. Schorr (Hamburg Observatory, Bergedorf, Germany) on December 31. The magnitude was then given as 15.
  • Apparition of 1931: Two predictions were provided for this apparition. G. van Biesbroeck calculated a new orbit for the 1913 apparition. He then applied perturbations by Jupiter and Saturn, as he integrated the orbit forward, and found a perihelion date of 1931 May 8.96. A. C. D. Crommelin took the definitive orbit calculated by F. E. Seagrave for the 1913 apparition, applied perturbations by Jupiter and Saturn, and predicted a perihelion date of May 7.4. S. B. Nicholson (Mount Wilson Observatory, California, USA) recovered the comet on 1931 September 17.51 when a photograph obtained with the 254-cm reflector revealed a stellar object of magnitude 16. Photographs obtained the next night confirmed that this was the expected comet. Nicholson subsequently found the comet on an earlier plate exposed on August 20.47. The actual perihelion date had come on 1931 April 30.08. The comet was at its brightest when recovered and slowly faded during the next few months. It was last detected on 1932 January 10, when Nicholson again photographed it with the 254-cm reflector. The magnitude was then estimated as 17.5. The comet never showed even a trace of coma during this apparition.
  • Apparition of 1948: During 1935, G. van Biesbroeck linked the orbits for the 1913 and 1931 apparitions, including perturbations by Jupiter and Saturn. He then integrated the orbit forward and predicted a perihelion date of 1948 December 19.13. S. B. Nicholson (Mount Wilson Observatory, California, USA) again recovered the comet, when his photograph on 1948 May 6.41 revealed a stellar object of magnitude 17.5. Interestingly, another stellar object was also present on the plate which had nearly the same motion. It took L. E. Cunningham to determine which object was the comet. G. van Biesbroeck (McDonald Observatory, Texas, USA) photographed the comet on September 3, 4, and 5, and noted a magnitude of 16, with a coma 3" across that was slightly elongated toward the north-northeast. The comet was last detected on December 3, when D. McLeish (Bosque Alegre, Argentina) photographed the comet with the 152-cm reflector.
  • Apparition of 1966: Predictions for this return were published by B. G. Marsden in 1965 and H. Raudsaar in 1966. Marsden predicted a perihelion date of 1966 December 10.06, while Raudsaar gave it as December 11.00. A. D. Andrews (Boyden Observatory, Bloemfontein, South Africa) recovered this comet on 1966 May 16.85. The magnitude was estimated as 17, and the comet was described as diffuse, without a condensation. Confirmation was obtained by M. J. Bester (Boyden Observatory) on May 17.88. The magnitude was again estimated as 17. These observations indicated the actual perihelion date was December 9.40. The comet was sparsely followed during this apparition. It passed closest to Earth on 1966 July 3. Z. M. Pereyra (Cordoba Observatory, Argentina) had acquired long exposures using the 152-cm reflector on June 23 and 24, and estimated the magnitude as 15.5-16. He noted the comet was stellar in appearance. No additional observations were acquired during the remainder of 1966. A single, 45-minute exposure was obtained by A. A. Hoag (Kitt Peak National Observatory, Arizona, USA) on 1967 August 7.4, using the 91-cm reflector. During 1968, Marsden wrote that the comet "was probably photographed [but] the image was very weak and has not yet been definitely identified with the comet."
  • The Rotation Period of the Nucleus: The comet's rotation period has been analysed by several observers. T. D. Fay and W. Z. Wisniewski (1985) acquired observations of the comet during 31 hours over parts of six nights during the period of 1984 June 18 to August 25. They said the observations were best represented by a rotation period of 1.053 days. W. Z. Wisniewski, T. D. Fay, and T. Gehrels (1986) stated the comet was monitored over 15 nights between 1984 June 18 to August 30 using both the 102-cm and 152-cm telescopes on Mt. Lemmon (Arizona, USA). They noted the comet was perfectly stellar during each observation and reiterated the 1.053-day rotation period, although they noted that a period of half this value "should not be ruled out." Using the observations they acquired during 1985 and 1986, Jewitt and Meech (1988) determined the rotation period of the nucleus as 12.67 hours. C. E. Delahodde, Meech, O. R. Hainaut, and E. Dotto (2001) used positions acquired by Meech from this apparition, as well as images during the 2002 apparition, and determined the rotation period as 12.75 hours.
  • Close approaches to planets: During the 19th and 20th centuries, this comet made two close approaches to Earth and five close approaches to Saturn. There will be one close approach to Earth and one close approach to Saturn during the 21st century.
    • 1.12 AU from Saturn on 1803 October 18
      • increased perihelion distance from 1.51 AU to 1.53 AU
      • increased orbital period from 17.34 to 17.56 years
    • 1.39 AU from Saturn on 1829 December 6
      • increased perihelion distance from 1.52 AU to 1.54 AU
      • increased orbital period from 17.41 to 17.62 years
    • 0.79 AU from Saturn on 1892 February 10
      • decreased perihelion distance from 1.55 AU to 1.52 AU
      • decreased orbital period from 17.72 to 17.54 years
    • 0.55 AU from Earth on 1913 September 2 (contributed to comet's discovery)
    • 1.59 AU from Saturn on 1918 March 13
      • decreased perihelion distance from 1.529 AU to 1.528 AU
      • decreased orbital period from 17.76 to 17.69 years
    • 0.83 AU from Saturn on 1980 June 7
      • increased perihelion distance from 1.54 AU to 1.55 AU
      • increased orbital period from 17.93 to 18.21 years
    • 0.87 AU from Earth on 1984 August 10
    • 1.63 AU from Saturn on 2006 June 2
      • increased perihelion distance from 1.55 AU to 1.58 AU
      • increased orbital period from 18.19 to 18.44 years
    • 0.79 AU from Earth on 2039 September 11