Copyright © 2000 by K. Horn
This image was obtained by Konrad Horn (Salem, Germany) on 2000 December 24. The image was composed of 30 60-second exposures obtained with a Genesis 100/500 telescope and an AUDINE CCD camera. The comet was then displaying a tail extending 6 arcmin toward PA 276°.
Horace Parnell Tuttle (Harvard College Observatory, Cambridge, Massachusetts) discovered this comet on 1858 May 3.1 (UT), as he was sweeping for comets. He described it as "very faint." The comet was then in Leo Minor and was later found to have been only 0.36 AU from Earth at the time and only one day from perihelion. These two conditions made this the perfect apparition for the discovery of this comet, but they also meant this faint comet would fade rapidly as it moved away from both the sun and Earth. It was last seen on June 2. Although astronomers realized this was a periodic comet, the short duration of visibility did not allow the orbital period to be determined with much precision. Subsequently, various computations indicated a period somewhere within the range of 5.8 to 7.5 years.
Michel Giacobini (Nice Observatory, France) discovered this comet during a routine search for comets with a 40-cm telescope on 1907 June 1. He described the comet as faint and ill-defined, with a diameter of 1.5 to 2 arc minutes. The comet was last detected on June 14, when Rambaud (Algiers Observatory, Algeria, North Africa) observed with a 31.8-cm equatorial. He described it as extremely faint, with a condensation. The short period of observation only allowed the computation of parabolic orbits. No one immediately noticed a similarity between this orbit and the orbit of Tuttle's 1858 comet; however, by 1928 A. C. D. Crommelin was devoting his attention to these two comets and was able to mathematically link the 1858 and 1907 apparitions. He provided predictions for a return in 1928 and 1934, but the comet was not found and was considered lost.
Lubos Kresák (Skalnaté Pleso Observatory) discovered this comet on 1951 April 24. He estimated the magnitude as 10, and described the comet as diffuse. By the first week of May enough positions had been acquired for the computation of an orbit and it was almost immediately realized that this comet was a return of those seen in 1858 and 1907. The comet basically held its maximum brightness for about a month before it began to fade. On this occasion, however, larger telescopes were in use and the comet was followed until August 9. This allowed a much more precise determination of its orbit and astronomers have been able to accurately predict its later returns.
Apparition of 1973: Despite the fact that this comet was accidentally discovered three times, the comet is particular famous among astronomers because of its 1973 apparition. Elizabeth Roemer and J. Q. Latta (Steward Observatory, Arizona, USA) recovered the comet on January 8 and determined the magnitude as 21.0. The comet steadily brightened thereafter, so that by May 20 F. Seiler (Munich, Germany) estimated the magnitude as 14. The surprise came on May 26 and 27. S. Ako (Siraishi, Japan) photographed an 8th-magnitude comet on May 26.51 (UT) and K. Mameda (Kobe, Japan) visually found a comet at magnitude 5 on May 27.51 (UT). Both observers thought they had found a new comet and reported their finds to the proper authorities. Meanwhile, Seiler went to photograph Tuttle-Giacobini-Kresak on May 27.92 (UT) and found the comet had brightened to magnitude 4 and exhibited a tail 0.1 to 0.2 degree long! The comet had experienced a brightness outburst amounting to about 10 magnitudes in the course of one week! The comet steadily faded throughout June, falling from magnitude 6 as the month began to at least magnitude 14 by month's end. On July 4.12 (UT), Richard E. McCrosky and Cheng-Yuan Shao (Harvard College Observatory, Agassiz station) estimated the magnitude as between 14 and 15. Milan Antal (Skalnaté Pleso Observatory) had taken an interest in this comet during late May and had acquired a number of observations through the end of June. When he next observed the comet on July 6.88 (UT), he found the comet was at a visual magnitude of 5.6. On July 7.97 (UT), Reginald Lawson Waterfield (Woolston Observatory, England) estimated the comet's magnitude as 4.5. Thus, the comet had experienced yet another 10-magnitude outburst! Fading was rapid thereafter, with magnitude estimates of 6.5 on July 8 and 9.5 on the 10th. The comet had faded back to its normal brightness by August and was last observed on September 23 at a magnitude of 17.
Apparition of 1978: The comet's next return came in 1978. Although this was not an especially favorable return, astronomers tried to observe the comet at every opportunity in case it began flaring in brightness again. Ultimately, observations covered the period of 1978 November 8 to 1979 January 7, but no unusual activity was noted and the comet's brightness never exceeded its predicted maximum brightness of 15.
Apparition of 2001: S. Nakano took positions from the years spanning 1978-1995 and predicted the comet would next return to perihelion on 2001 January 6.98. The appearance of the comet in late 2000 and early 2001 was not expected to be one of the best. Although the comet was expected to reach magnitude 12 by early January 2001, the elongation of 42 degrees and declination of about -15 degrees was not going to made it an easy target, especially for northern hemisphere observers. The comet was at a higher declination and nearly 50 degrees from the sun during November 2000 and observations shortly after mid-month revealed the comet's brightness was near magnitude 15, which was near the predicted value. It then had a coma less than 0.5 arc minute across. It was expected that the comet would brighten to magnitude 14 by the end of the month, but observers were indicating differently. On November 27 A. Hale (New Mexico) and K. Yoshimoto (Japan) found the comet near magnitude 10 and estimated the coma diameter as 2-3 arc minutes across. Numerous additional observers reported the comet's magnitude between 10 and 11 into the first days of December. Later in December, Kamil Hornoch and Jakub Cerny independently noted the comet had undergone another outburst, taking it to magnitude 7.6-7.7.
Close approaches to planets: The comet experienced five close approaches to Earth and two close approaches to Jupiter during the 20th century. It makes two close approaches to Earth and one close approach to Jupiter during the first half of the 21st century.
- 0.85 AU from Earth on 1907 May 29
- 0.90 AU from Earth on 1940 June 20
- 0.50 AU from Earth on 1951 May 17
- 0.27 AU from Earth on 1962 April 12
- 0.85 AU from Earth on 1973 June 4
- 0.37 AU from Jupiter on 1975 June 9
- decreased perihelion distance from 1.15 AU to 1.12 AU
- increased orbital period from 5.56 to 5.58 years
- 0.67 AU from Jupiter on 1988 February 16
- decreased perihelion distance from 1.12 AU to 1.07 AU
- decreased orbital period from 5.58 to 5.46 years
- 0.94 AU from Earth on 2006 July 6
- 0.14 AU from Earth on 2017 March 27
- 0.52 AU from Jupiter on 2046 September 19
- decreased perihelion distance from 1.08 AU to 1.07 AU
- increased orbital period from 5.49 to 5.50 years
Copyright © 2000 by Akimasa Nakamura
This image was obtained by A. Nakamura (Kuma Kogen Astronomical Observatory, Japan) on 2000 November 28.86 UT using a 60-cm, f/6 reflector and CCD. The comet was then undergoing an outburst in brightness.
Copyright © 2006 by G. W. Kronk
This image was obtained by Gary W. Kronk (St. Jacob, Illinois, USA) on 2006 June 4. The image was composed of nine 30-second exposures obtained using a 20-cm Meade LX200 GPS and a MallinCam. The image was processed using Registax and PhotoShop.