The similarity between C/2006 P1 (McNaught) and C/1743 X1 (De Chéseaux)

Mark Kidger

 

Many people have been struck by the obvious similarities between the famous six-tailed, “peacock fan comet” C/1743 X1 (De Chéseaux) which is more correctly named Comet Klinkenberg, or Klinkenberg-De Chéseaux and C/2006 P1 (McNaught). Two famous woodcuts show the comet with its tails projecting over the horizon. For many years Comet De Chéseaux has been held up as an example of a quite unique many-tailed object, although there was no obvious explanation as to why it should be so different to other comets. The remark-able observations of Comet McNaught have provided a simple and obvious explanation.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The composition (left) shows this comparison graphically. The top image is by Carlos Labordena from Castellón (Spain) on January 20^th. The image was taken at 18:50UT. At that time the comet was in declination –40º and 26º below the horizon. At least four synchronic bands can be seen, mixed with the zodiacal light. The second image (lower left) is a reference image of the comet on January 19^th. Taken by Rob McNaught from Siding Spring, it shows just what a magnificent object his comet was in the southern sky after perihelion. The image to the lower right is the lesser known of the two wood cuts of Comet De Chéseaux reflected left-right. This shows the comet at 4 in the morning on March 9^th 1744. The tail projects some 25º above the eastern horizon, almost reaching Delphinus, with the comet’s head calculated to be 24º below the horizon at this time. The com-et was in declination –18º at this time and, even at sunrise, the head of the comet was 4º below the horizon. The circumstances of observation were thus very similar to those for Comet McNaught in the January 20^th image. Note how the structure of the tail is almost identical for the two comets, with the shortest tail in the anti-solar direction and bands reaching increasing distances from the head further as we move further from the anti-solar direction.