The expected brightness of the comet C/2020 F3 (NEOWISE).
니오와이즈 (C/2020 F3) 혜성의 예상 밝기.
Magnitude data: Central Bureau for Astronomical Telegrams. Electronic Telegram No. 4804. (CBET 4804).
Epoch = 2020 July 10.0 TT
T = 2020 July 3.68072 TT, Peri. = 37.27545
e = 0.9991822, Node = 61.01042 (2000.0)
q = 0.2946898 AU, Incl. = 128.93737
Photometric power-law parameters H = 7.0 and 2.5n = 12.5. Heliocentric distance 1.6 AU < r.
Total apparent magnitude m = H + 5 log10 d + 2.5 n log10 r .
Comets’ intrinsic brightness is usually expressed in terms of the absolute total magnitude H, which is related to the apparent magnitude m using the relation H = m − 5 log10 d − 2.5 n log10 r. Here d and r are the geocentric and heliocentric distances, respectively, and n is the photometric index, which strongly depends on the strength and nature of a given comet’s activity. For an inactive (asteroidal) body, n = 2. Often n = 4 is assumed for comets, leading to the conventional absolute magnitude H10. However, comets show great diversity in their activity, and n indexes ranging from 1 to 10 have been reported for different comets (with even more extreme values on occasion). (Vokrouhlický, Nesvorný, & Dones 2019, AJ, 157, 181).