26 May 2021
Perihelion Distance (q)
Aphelion Distance (Q)
Click for NASA orbit diagram
Hills Observatory: 1 January 2013 to 10 June 2019
Jean Louis Pons (Observatory of Marseille, France) discovered this comet on 12 June 1819. The
comet was then in Leo and was described as small, with a central condensation.
Friedrich August Theodor Winnecke (Bonn, Germany) accidentally rediscovered this comet on 9
March 1858. It was then located in Ophiuchus and was described it as a pale and diffuse
nebulosity, about 3 arcmin across.
The comet was particularly well placed during its discovery apparition, but its most significant
event, a close approach to Earth on 21 August 1819 (0.1318 AU) was missed. Following its
discovery the comet was followed until lost in evening twilight after 22 July. The comet took on
a southwestern motion thereafter, and was in southern skies by the time it emerged from the
sun's glare. On 31 August it reached its most southerly declination of -43.6°.
Using only three positions obtained during the period of 9 to 13 March 1858, Krüger computed a
parabolic orbit that he immediately recognized as so similar to Pons' comet of 1819 that he
suggested they were identical. Shortly thereafter, Winnecke applied the orbit of the 1819 comet
to the available positions and found an almost perfect agreement by assuming a perihelion date
of 2 May 1858, and slightly increasing the inclination.
Predictions were made for the 1863 return, but they revealed the comet was very poorly placed
for recovery and the comet was subsequently missed. Predictions for the 1869 return showed the
comet would be much more favorably placed. The comet was subsequently recovered on 10 April
1869 by Winnecke, very close to the predicted positions. The comet passed 0.25 AU from Earth
on 8 July and observers saw a coma 10 arcmin across which contained a nucleus of magnitude
8. A short tail was also seen.
Since the 1869 appearance, the comet has only been missed on three occasions (1880, 1904,
Perturbations by Jupiter have steadily increased the comet's orbital period and perihelion
distance since its first successfully predicted recovery in 1869. Close approaches occurred in
November 1882 (0.44 AU), November 1894 (0.45 AU), December 1906 (0.42 AU), November
1918 (0.36 AU), and July 1930 (0.47 AU). In 1869 the period was 5.59 years and perihelion
distance was 0.78 AU, while in 1996 they were 6.37 years and 1.26 AU.
For a few years the perturbations by Jupiter enabled strong displays of meteors to be seen
around June 28 of the years the comet arrived at perihelion. The meteor stream became known
as the June Boötids, but was occasionally also known as the Pons-Winneckids. Very strong
displays were noticed in 1916, 1921, and 1927, which also marked three consecutive perihelion
returns for the comet. In the latter year, rates reached 500 per hour at one point. Continued
perturbations by Jupiter have moved the comet and its meteor stream into slightly different
orbits and the June Boötids have been hardly noticeable in recent years.
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