Comet C/1998 M5 (LINEAR) was discovered on June 30, 1998. The brightness of this comet, situated in Pegasus, was given as 16m, but is likely to have been 13.5m. A 0.5' coma and a 2-4' long tail were reported (IAUC 6959/61). This comet passed the North Pole and Polaris on March 15, 1999. The pole passage took place around 10h UT at a distance of 10' followed by the passage of Polaris three hours later (distance: 33')! Do you remember comet Panther (1980u = 1981 II) in 1981, which did the same? It is highly probable, as Alan Hale and Jost Jahn pointed out, that comet C/1998 M5 (LINEAR) is a fragment of comet Panther, as comet C/1996 Q1 (Tabur) was one of comet Liller (1988a)! Because it follows comet Panther by nearly exactly 18 years, it follows the same path as Panther did (AFZ 596/597).
Comet C/1998 M5 (LINEAR) did not exhaust its propellant as comet Tabur did, passing the Pole as a well-condensed object of magnitude around 9.5. This means, that comet C/1998 M5 (LINEAR) was about 1m fainter than comet Panther, which, however, exhibited a somewhat strange brightness evolution with a very small n.
Based on 180 observations of 15 FG observers and 390 international observations, the brightness evolution can be described via the formula
During the first months the apparent coma diameter grew only slowly, starting at 1.8'. After November however, the increase accelerated, topping at 4.5' in the second half of March. At the end of May it had again shrinked to 2.5'. The absolute diameter of the coma grew continuously from 160.000 km to 320.000 km until the end of March. Since then the diameter hovered around this value. Comet LINEAR showed a very constant degree of condensation (DC 4). It was only after the passage of the celestial pole that it decreased to DC 3. Visual observations of the tail, predominately pointing south, were very rare, reporting a maximum length of not more than 3-4' (about 500.000 km).
Total Brightness and Coma diameter
Andreas Kammerer
