Analysis of Comet Apparitions

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C/2020 F3 (NEOWISE)

On images taken by the satellite NEOWISE in the infrared on Mar. 27, 2020 a comet was discovered in the southern part of the constellation Puppis. Follow-up observations of comet C/2020 F3 (NEOWISE) showed a quite diffuse coma of diameter 2' and of total magnitude 16.0. The comet will reach its perihelion at the small solar distance of 0.30 AU on July 3, 2020. It may reach 8th magnitude, but will then be located close to the Sun (CBET 4740/42). In addition, the derived absolute magnitude is clearly below the Bortle-limit, thus making a disintegration of this comet on its way towards perihelion likely. Earth will cross the comet's orbital plane on May 22.

During the first four weeks the comet brightened extremely rapid, reaching magnitude 11.0 on Apr. 10, 2020. Thereafter the brightness increased much more slowly, but still above average, as 89 observations from 11 observers (until June 10, 2020) indicate. In the days it disappeared in the twilight (about June 10) the comet was of magnitude 7.0. If it should hold this development until perihelion it would peak at magnitude 0! The appropriate formulae are:

t < -70d: m = 0.8 mag + 5×log D + 42.5×log r
t > -70d: m = 7.0 mag + 5×log D + 13.5×log r

Development of the heliocentric magnitude

The final pre-perihelion observations are significantly below the brightness development during those days. This could hint towards a break in the development (with the parameter values totally undefined due to the few observations) or its just the result of the then deteriorating observing conditions. Additional observations can not be expected until the comet will appear above the evening horizon around July 10. It will be very thrilling just how bright it will then be. All values between 0 mag and 5 mag are possible and even a disintegration of the comet.

Total Brightness and Coma Diameter

Between Apr. 10 and May 20 the coma diameter increased from 2' (150.000 km) to 8' (575.000 km). Whereas the coma was rather diffuse (DC 2-3) until mid-May, it condensed during the following weeks, showing a degree of condensation of DC 5-6 in the first week of June. So far no tail was observed visually.

Andreas Kammerer