During winter 2009/10 comet 81P/Wild will move from Leo into Virgo, being a morning object. In spring 2010 it will loop in eastern Virgo, being visible during the whole night. It is expected to peak around 9.5 mag.

According to 19 observations by 5 members of the German Comet Section and 200 international observations the comet experienced a rather unusual brightness evolution during this apparition. Pre-perihelion the evolution can only be represented by assuming a constant activity over the whole time interval. Post-perihelion the comet faded on average. The brightness peaked at 9.2 mag at the end of March 2010. The appropriate formulae are:

Not surprisingly the apparent coma diameter did not increase significantly before perihelion: from 2.5' in September 2009 to 3.5' at the end of February 2010. Thereafter it increased rapidly to the maximum of 6', maintained between the end of March and the end of April. At the beginning of June it measured 3.5' and in mid-July 1.5'. The absolute coma diameter evolved very differently. Measuring 225.000 km at the end of September 2009 it shrunk during the following months, measuring 175.000 km between mid-March and mid-June. It then shrunk to 100.000 km in mid-July. Pre-perihelion the degree of condensation was constant at DC 3. Immediately after perihelion the coma was more condensed (DC 4-5), getting more diffuse during the following weeks (mid-July: DC 3-4). A visual tail could be detected between mid-December 2009 and the end of May 2010, reaching 15' (3 Mio. km) and pointing constantly towards WNW.

Total Brightness and Coma Diameter

FGK observations