Analysis of past comet apparitions

22P/Kopff

2009


Comet 22P/Kopff (P=6.44a) will be observable during spring/summer 2009, moving from Sagittarius to Aquarius. Thus it will be a low-altitude object for mid-European observers. According to the ICQ it should reach 8.0 mag.

Due to its southerly declinations the comet was not an easy object from mid-European latitudes. Therefore the following analysis is based on only 19 observations by 8 members of the German Comet Section and on 140 international observations. These indicate a non-standard brightness evolution. Even the distinction between the evolution prior and after perihelion is not sufficient. Instead the observations show a surprisingly rapid decline of the heliocentric magnitude, beginning at perihelion, which slowed with passing time. In September and October the heliocentric magnitude was constant. Near the end of the apparition the heliocentric magnitude even seems to brighten slowly - however this development is based on only one observer, thus being rather uncertain.

Post-perihelion evolution of the heliocentric magnitude

Thus the following formula for the post-perihelion period simulates the evolution only unsatisfactorily. The maximum brightness of 8.9 mag was reached at perihelion. The appropriate formulae are:

pre-perihelion: m = 4.4 mag + 5×log D + 22×log r
post-perihelion: m = 9.4 mag + 5×log D + 4.5×log r

The apparent coma diameter increased from 1.5' at the beginning of the apparition to 8' at the end of June. This value was hold until end of August. Thereafter it shrunk, reaching 2' at the end of November. The absolute coma diameter increased from 110.000 km at the start of the apparition to 340.000 km in mid-May. This value was hold until the beginning of July. Thereafter it shrunk slowly, reaching 275.000 km at the end of August and 175.000 km at the end of November. The coma was rather diffuse, with the degree of condensation about DC 2-3 in summer and DC 2 at fall.

Total Brightness and Coma Diameter

Andreas Kammerer

FGK observations


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