28P/Neujmin (0028P)

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Type: Periodic Perihelion date: 11 March 2021 Perihelion distance (q): 1.6 Aphelion distance (Q) : 12.4 Period (years): 18.4 Eccentricity (e): 0.77 Inclination (i): 14.3 JPL orbit diagram COBS lightcurve G. N. Neujmin (Simeis Observatory, Crimea, Ukraine) discovered this object on a photograph exposed on 3 September 1913, 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 5 September and gave the magnitude as 10.8. On 7 September, 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 7 September. At the time of discovery, the 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 31 December. The magnitude was then given as 15. Apparition of 1931: S. B. Nicholson (Mount Wilson Observatory, California, USA) recovered the comet on 17 September 1931 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 20 August. The actual perihelion date had come on 30 April 1931. The comet was at its brightest when recovered and slowly faded during the next few months. It was last detected on 10 January 1932, 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: S. B. Nicholson (Mount Wilson Observatory, California, USA) again recovered the comet, when his photograph on 6 May 1948 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 3, 4, and 5 September, 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 3 December, when D. McLeish (Bosque Alegre, Argentina) photographed the comet with the 152-cm reflector. Apparition of 1966: A. D. Andrews (Boyden Observatory, Bloemfontein, South Africa) recovered this comet on 16 May 1966. 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 17 May. The magnitude was again estimated as 17. These observations indicated the actual perihelion date was 9 December. The comet was sparsely followed during this apparition. It passed closest to Earth on 3 July 1966. Z. M. Pereyra (Cordoba Observatory, Argentina) had acquired long exposures using the 152-cm reflector on 23 and 24 June, 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 7 August 1967, 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 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 18 June to 25 August 1984. 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 18 June 1984 to 30 August 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: • 1.12 AU from Saturn on 18 October 1803; 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 6 December 1829; 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 10 February 1892; 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 2 September 1913 (contributed to comet's discovery) • 1.59 AU from Saturn on March 13 1918; 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 7 June 1980; 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 10 August 1984 • 1.63 AU from Saturn on 2 June 2006; 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 11 September 2039 Observations (VEMag = visual equivalent magnitude) Date 10x10 mag Error VEmag Coma ' 21-Aug-21 16.5 0.4 09-Sep-21 17.42 0.09 16.5 0.4