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On July 7, 2018 the ASASSN team discovered a comet of magnitude 16 in the central part of Eridanus. Follow-up observations of comet C/2018 N2 (ASASSN) showed a strongly condensed 25" coma and a 15" tail in p.a. 220°. The comet will pass perihelion on Nov. 10, 2019 at a distance of 3.12 AU, expected to reach magnitude 11 (CBET 4534). It should be brighter than 16 mag until spring 2021, brighter than 13.5 mag between mid-2019 and mid-2020. During the latter time span it moves from Aries into Cepheus. Thus it will be well placed for mid-European observers during the most interesting weeks. Assuming an average activity parameter (n=4) the absolute brightness is magnitude 4.0, hinting towards a large object, which, alas, will not come close to the Sun.
The development of this comet can be analysed based of 385 observations from 48 observers. The brightness estimates can be described quite well with the following formulae, which indicate an under-average development pre-perihelion and a significantly more rapid decline of the activity post-perihelion.
pre-perihelion: m = 6.8 mag + 5×log D + 6.0×log r post-perihelion: m = 5.0 mag + 5×log D + 9.7×log rThus a maximum brightness of 11.5 mag around Oct. 25, 2019 can be derived.
Total Brightness and Coma Diameter
The coma diameter measured 0.9' (175.000 km) until August 2019. During the following months it increased steadily, reaching a maximum of 2.5' (290.000 km) at the turn of 2019/20. Thereafter it decreased rapidly until the end of April, when it reached just 0.7' (125.000 km), then much more slowly until the start of November. In 2018 the coma showed a degree of condensation of DC 3. Between August and November 2019 it was significantly condensed (DC 4-5), but thereafter grew ever more diffuse until the end of April (DC 2-3). Thereafter it did not decrease further. A tail, which reached a maximum length of 9' (4 Mio. km) in November 2019, could be observed between June 2019 and February 2020. Until October the tail pointed constantly towards South, turning towards Southeast until the turn of 2019/20, pointing constantly in this direction during the following weeks.
Andreas Kammerer