Within days of its rediscovery comet 37/Forbes could be observed visually. Only 11 reports were received from 3 FG members until the start of November. Adding 95 international observations, first results can be presented. The brightness evolution must be divided into two, probably three phases. The following diagram suggests an outburst in brightness between T+25d and T+55d, with the maximum around T+40d. The brightest estimates, however, are only supported by 2 observers. That something must have happened around this time can be derived from the fact, that the light-curve shows a definite displacement before and after the time in question. The current brightness formulae are:
resulting in a maximum brightness of 11.9m (in case of a comfirmed outburst of 10.9m). The apparent coma diameter increased from 0.7' at rediscovery to a maximum of 2.0' at the beginning of August, decreasing to 1.5' in mid-October. The absolute coma diameter was at 50.000 km at first, then grew to 90.000 km at the beginning of July but decreased to 75.000 km in mid-October. The degree of condensation increased during the apparition slightly from DC 2-3 to DC 3.
Total Brightness and Coma diameter
The perihelion distance varies between 1.2 AU and 1.9 AU. The minimum value will be reached between 2100 and 2150, when two close encounters with Earth will occur (July 2131: 0.25 AU, July 2142: 0.21 AU) (AFZ 660).
Andreas Kammerer
