Surprisingly bright got comet C/1999 L3 (LINEAR) in January/February, based on 20 observations by 5 FG members and 90 international observers. Originally predicted with a maximum brightness around 13m it actually reached 11m.
According to these data this - at first almost asteroidal - object seems to have evolved very rapidly while approaching perihelion. Excluding the estimates of the first half of February - which indicate a short-lived brightening of 0.5m - the brightness evolution can be best represented with the parameters m0=8.5m/n=4, although there exists a broader range of alternative parameters, which also yield plausible results.
The apparent coma diameter increased from 0.5' at mid-November to 3.0' at the end of January. After that it decreased similar fast and was only 1.5' at the begin of March and 1' at the end of April. The absolute coma diameter increased within a short time from 60.000 km to 120.000 km, reaching 140.000 km at the end of January, decreasing slowly thereafter to 110.000 km at the start of April. The coma was only slightly condensed (DC 2), condensing in January to (DC 4-5) but getting more diffuse afterwards.
Total Brightness and Coma diameter
Due to gravitational disturbances the period of this comet will increase from 622 years to 685 years during this perihelion passage (AFZ 714).
Andreas Kammerer
