E. Guido, G. Sostero and P. Camilleri recovered comet P/2001 MD7 (LINEAR) on Mar. 17, 2009 with the 25cm-telescope at RAS-observatory. Comet P/2009 F3 (LINEAR) was positioned in the northeastern corner of Sagittarius and showed a diffuse 15" coma of magnitude 18. It will pass perihelion of its orbit with a period of 7.83 years at the beginning of September and could reach magnitude 12 (IAUC 9031). It has received the permanent designation 217P/LINEAR (IAUC 9038).
The comet showed a surprisingly positive evolution during summer/fall 2009, according to 20 observations by 6 members of the German Comet Section and 105 international observations. Showing a very rapid brightening prior to perihelion it faded much slower thereafter. The evolution can be well described by the formulae:
pre-perihelion: m = 9.6 mag + 5×log D + 19×log r post-perihelion: m = 10.4 mag + 5×log D + 7.5×log rThe maximum brightness of 10.0 mag was reached around Sep. 10.
Total Brightness and Coma Diameter
The diameter of the coma increased from 0.6' (25.000 km) in June to 3.8' (100.000 km) at the start of September. This value was constant until mid-November. Thereafter it shrunk continuously, measuring 1' (70.000 km) at the start of February 2010. During the whole apparition the coma grew more and more diffuse. The degree of condensation was estimated as DC 5-6 at the start of the apparition, but as DC 3 in January 2010. The tail was visually quite obvious, oriented in westerly directions. Reports were published between mid-August and the end of October with the tail reaching a maximum length of 10' (325.000 km).
Andreas Kammerer
