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A few days after the discovery of an asteroidal object of magnitude 21 on Mar. 19, 2021 in the constellation Bootes (by the LEMMON and PANSTARRS teams, respectively) it was realized that the object moves on a parabolic orbit. Beginning in December 2021 a cometary morphology is observed. Comet C/2021 F1 (LEMMON-PANSTARRS) showed a strongly condensed coma of total magnitude 18. On Jan. 7, 2022 an inner coma of diameter 15" and an outer coma of 60" diameter was observed, with the latter elongated towards North. On Jan. 15 CCD-observations showed a 3.7' coma of total magnitude 14.0. Alan Hale imaged the coma via CCD on Jan. 28, measuring a 1.0' inner coma (displaying a distinct central condensation) and a vague outer coma. On Jan. 30 Charles Morris measured a 4.4' coma of total magnitude 13.0 on a CCD image. The comet will pass perihelion at the solar distance of 1.00 AU on Apr. 6, 2022, expected to peak at 12.5 mag (CBET 5095). The comet already passed Earth (at 1.41 AU) in mid-February and will be positioned at the opposite side of the Sun at perihelion. Its orbit is perpendicular to the ecliptic and will cross it at the start of May. The comet should be brighter than 16 mag until August 2022. Between January and August 2022 it will move through the constellations Corona Borealis, Hercules, Lyra, Cygnus, Lacerta, Andromeda, Pisces (perihelion), Cetus, Eridanus, Caelum and Pictor. It can be followed from mid-European locations until end of March – at the morning and evening sky.
The comet peaked at magnitude 9.5 – 3 mag brighter than predicted. The published observations cover the pre-perihelion interval much better than the post-perihelion one. Thus the pre-perihelion results are much more secure than the post-perihelion ones. The estimates indicate a different development pre- and post-perihelion with high probability, with the comet brightening much faster than it faded. Based on 61 observations from 23 observers the following brightness parameters result:
pre-perihelion: m0 = 8.2 mag / n = 8The maximum brightness of 9.5 mag was reached at the opening of April 2022.
Total Brightness and Coma DiameterPre-perihelion the coma diameter increased from 1.5' (90.000 km) to 3.5' (275.000 km). For the post-perihelion period no data has been published. This is also true for the degree of condensation, which increased from DC 1 to DC 3-4 pre-perihelion. No tail was observed.
Andreas Kammerer