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D/1895 Q1 (Swift)


L. Swift (Lowe Observatory, California, USA) discovered this comet in Pisces on 1895 August 21.42. He described it as faint and round, with a bight elliptical central condensation. Interestingly, Swift found the comet while trying to secure a more accurate position for the last nebula he had discovered at Warner Observatory (Rochester, New York, USA). Upon setting the 41-cm refractor on the position of the nebula, Swift looked through and immediately noticed "a beautiful comet instead of the expected nebula." E. E. Barnard (Lick Observatory, California, USA) confirmed the discovery on August 22.31.

Historical Highlights

  • This comet was discovered on the day it passed perihelion and was closest to Earth (0.35 AU) on August 31. Therefore, not long after astronomers began observing this comet, it had started to fade; however, astronomers still managed to keep the comet under observation for over five months, or until February 6. Magnitude estimates were not very common place, with only J. Holetschek (Vienna, Austria) and P. Chofardet (Besançon, France) providing estimates for this comet. Holetschek gave the magnitude as 11 on August 24 and 27, and 12 on August 30. Chofardet gave the magnitude as 13 during the period of September 24-29. After September, all further indications of the comet's brightness were simply descriptive and were made with refractors whose objectives ranged from 25-cm to 51-cm. This latter telescope information is important because there is an indication that the comet was brighter than what the above estimates indicate. During the period spanning August through November, observers were reporting a coma diameter of 1-2 arc minutes, except on two occasions: on August 25, G. Le Cadet (Lyon, France) said the coma was 5' across in the 32-cm refractor and on November 15, H. A. Howe (Chamberlin Observatory, Colorado, USA) noted a "very tenuous" coma 9 arc minutes across in the 51-cm refractor. What this indicates is that there was more to this comet than what most people were seeing, so that the comet was apparently a very diffuse object. Such objects are not well suited for large refractors. Another indication that the comet was brighter and not suited for large telescopes came shortly after mid-September. Le Cadet saw the comet with averted vision in a 32-cm refractor on September 19, while W. H. Robinson (Radcliffe Observatory, Oxford, England) noted it was extremely feeble in a 25-cm refractor on the 20th. Interestingly, during the period of September 18-20, V. Cerulli (Teramo, Italy) noted it was visible in a 6-cm finder! Howe was the only observer to provide physical descriptions during December. Still using the 51-cm refractor, he said the comet was nearly blotted out by moonlight on the 5th, was very hard to see in dark skies on the 10th, and was "not excessively difficult" to see on the 20th. Although Howe stated that the comet should easily be followed during January, bad weather or poor sky conditions prevented him from continuing observations. The comet was last seen at Lick Observatory, when the position was measured by W. J. Hussey on February 6.14 and by W. W. Campbell on February 6.19.
  • The first parabolic orbit was calculated by W. J. Hussey using positions obtained on August 22 to 24. The resulting perihelion date was 1895 October 5.70. The orbit was refined as the observation arc increased, with A. Berberich and L. Boss independently using three positions obtained between August 22 and 25, and determining perihelion dates of September 3.83 and August 25.04, respectively. The first elliptical orbit was calculated by Berberich using positions obtained during the period of August 22 to 28. He determined the perihelion date as August 25.96 and the period as 3.22 years. Berberich said the elements were still somewhat uncertain and that the likely period would probably be 5 or 6 years. Berberich revised his calculations nearly 10 days later. On this occasion, he took positions spanning the period of August 22 to September 16, and determined the perihelion date as August 21.35 and the period as 7.06 years. Additional orbits were calculated by L. Schulhof, during 1895, and H. R. Morgan, during 1898, which slightly revised the perihelion date to August 21.3 and the period to 7.2 years. Despite several later predictions, the comet has never been recovered. The latest redetermination of the 1895 orbit was calculated by N. A. Belyaev and O. J. Stal'bovskij in 1972.
  • Except for the orbital calculations noted above, not much else had been written about this comet since its final observation...at least until 2006. Paul Wiegert (University of Western Ontario, Canada) had been examining a mystery. He was trying to find out what the space probe Mariner 4 encountered on 1967 September 15. It had been about two years since the space probe had passed by Mars, when suddenly it encountered an intense meteor storm that lasted about 45 minutes. This event was brought to Wiegert's attention by Bill Cooke (NASA's Meteoroid Environment Office, Huntsville, Alabama, USA), who noted that the meteor storm was more intense than anything experienced on Earth. Wiegert found that Mariner 4 would have passed about 20 million miles from the head of comet Swift. He suggests that the comet was possibly lost because it broke up and that it was the debris field that Mariner 4 encountered. Admittedly, Wiegert notes that this is not to be accepted as a definitive answer to the Mariner 4 event, as the comet's orbit for the 1895 apparition is not precisely known, leading to a large potential error in the comet's expected position on 1967 September 15.
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