On Apr. 22 the LINEAR-Team announced the discovery of just another cometary object. Comet C/1999 H3 (LINEAR) was positioned near the border of Cygnus and Lyra. This 15.5m object again showed a small coma (20") and a short broad tail (13"). It passed perihelion in mid-August at the quite large distance of 3.5 AU (IAUC 7151/52). Thus it seemed logical that it would not get any brighter. It therefore was very surprising when visual observers reported the comet to be of magnitude 14 at the beginning of May. During the following weeks the brightness increased slowly, reaching 13.0m at perihelion.
Only 20 observations of three members of the German comet section were received. Based on these and 135 international observations the brightness evolution shows the following time-dependent correlations as follows:
The apparent coma diameter was about 1.2' at the beginning, increasing to 1.4' in August 1999, decreasing again to under 1.0' at the end of visibility. Similarly the absolute coma diameter increased from 200.000 km to 230.000 km, decreasing to 150.000 km at the beginning of May 2000. The coma was only moderately condensed, the degree of condensation decreased from DC 3-4 at the beginning of the visual observations to DC 2-3 at the beginning of the year 2000.
Total Brightness and Coma diameter
Andreas Kammerer
