3 November 2018
Perihelion Distance (q)
Aphelion Distance (Q)
Click for NASA orbit diagram
Hills Observatory: 1 January 2013 to 16 November 2018
L. Swift (Warner Observatory, Rochester, New York, USA) was engaged in the search for nebulae
when he found an object of cometary appearance on 17 November 1889. It was located very
close to Xi Pegasi and was described as "Pretty faint, large, little elongated." Swift said no motion
was detected during the next 30 minutes and he suspected it was one of two nebulae that W.
Herschel discovered near this star late in the 18th century, although Swift's position did not agree.
He reobserved the object on 17 November and noticed it had moved, whereupon he sent a
discovery announcement. After a second periodic comet was found by Swift in 1895, this comet
officially became known as "Swift 1".
Tom Gehrels (Palomar Mountain Observatory, California, USA) discovered this comet on a plate
exposed with the 122-cm Schmidt telescope on 8 February 1973. He estimated the magnitude as
19, and described the comet as diffuse and 30 arc seconds across, with a sharp condensation,
but no tail. Gehrels confirmed the discovery on 9 February.
Following the comet's rediscovery in 1973, B. G. Marsden noted a similarity between initial orbit
calculations and that computed for the lost periodic comet Swift 1. He used 22 observations of
Swift 1, which were obtained during 1889-1890, and redetermined the orbit, then applied
perturbations by Jupiter to Pluto and integrated the orbit up to 1973. The result was an orbital
period of 8.38 years. Further positions enabled Marsden to revise the perihelion date to 31
August and the period to 9.23 years. Marsden said the comet passed close to Jupiter in 1910
(0.7 AU) and 1924 (1.0 AU), and that the comet would have had favorable perihelion passages
in September 1935 and December 1944, which would have resulted in a maximum brightness of