Manzini, F.F.ManziniOldani, V.V.OldaniOchner, P.P.OchnerBarbotin, E.E.BarbotinBEDIN, LuigiLuigiBEDINBehrend, R.R.BehrendFardelli, G.G.Fardelli2023-01-232023-01-2320210035-8711http://hdl.handle.net/20.500.12386/32991The recent close approach of comet C/2020 F3 (NEOWISE) allowed us to study the morphology of its inner coma. From the measurement of the dust ejection velocity on spiral structures expanding around the nucleus, we estimated a mean deprojected expansion velocity V<SUB>d</SUB> = 1.11 ± 0.08 km s<SUP>-1</SUP>. Assuming that a new shell formed after every rotation of the comet, a period of 7.8 ± 0.2 h was derived. The spin axis orientation was estimated at RA 210° ± 10°, Dec. +35° ± 10°. The coma morphology appears related to two strong, diametrically opposite emissions located at mid-latitudes on the nucleus. A qualitative modelling of the coma produced consistent results with a wide range of dust sizes (0.80-800 μm), with inversely correlated densities (0.003-3.0 g cm<SUP>-3</SUP>). Images taken with Vj and r-Sloan filters showed a greater concentration of dust in the first two shells, and an increasing density of radicals emitting in the B and V band passes from the third shell outwards. Striae-like structures in the tail suggest that dust particles have different sizes.STAMPAenArticle10.1093/mnras/stab18492-s2.0-85118164452https://academic.oup.com/mnras/article/506/4/6195/6311818http://arxiv.org/abs/2109.02039v12021MNRAS.506.6195MFIS/05 - ASTRONOMIA E ASTROFISICA