Visual observations of comet C/1999 J3 (LINEAR), which was discovered by the LINEAR team on May 12/13, showed it 3m brighter in mid-June than predicted (IAUC 7229). This evolution continued, resulting in a much more interesting earth passage on Oct. 18 at a distance of 0.508 AE (for which, at first, a magnitude of 11m was predicted) than expected. Due to the morning apparition and the uncooperative weather only 35 observations made by 10 FG members were reported. In combination with 225 international observations, it becomes clear, that the brightness evolution was more rapid prior to perihelion than afterwards, aiding in making it a well observable object during its earth passage. The following formulas apply:
yielding a maximum brightness of 7.4m! While the maximum apparent coma diameter of 10' was observable during the passage of the Earth, the maximum absolute diameter was reached at perihelion. The coma diameter increased from 170.000 km to 290.000 km at perihelion, but decreased until the beginning of December to 170.000 km. At first the coma was only moderately condensed (DC 2-3), getting more condensed (DC 5) close to perihelion. Since then the coma got more diffuse and the DC-value decreased to DC 2. Some visual tail observations (up to 0.25°) were reported in the first half of October.
Total Brightness and Coma diameter
A meteor shower predicted by Rao for November 11 did not occur (AFZ 703). Earth passed the node at a distance of only 0.011 AU, but the dust of LINEAR, a non-periodic comet, has had too little time to spread sufficiently.
Andreas Kammerer
