SPECIFIC FEATURES OF STRUCTURES IN THE INNER COMA OF COMET C/2017 T2 (PANSTARRS) AS OBSERVED WITH THE OMT-800 TELESCOPE OF THE ODESSA OBSERVATORY TELESCOPE NETWORK

Анотація

Observations of the comet were
carried out using the OMT-800 telescope (the primary
mirror diameter D = 80 cm; the focal length F =
214 cm) of the Odessa Observatory telescope network
from January to June 2020. Image processing was per-
formed through standard methods using subtraction of
dark and flat field frames. The resulting frames were
employed to analyse the morphology of the cometary
inner coma using digital filters. Isophotes of the coma
and images of its structures appearing as fans and jets
were obtained. The presence of a strong fan, which
distorts the coma’s standard appearance and makes
it elongated perpendicularly to the Sun-comet line, is
observed over the period from January to April. Later
on, a weak jet that hardly affects the coma’s standard
shape appears to replace the fan. The jet reaches its
peak intensity near perihelion and then gets fainter
rapidly. Such behaviour of the coma structures is
indicative of the presence of two active areas on the
cometary nucleus surface, for which the matter outflow
is governed by the Sun illumination conditions. One
of these areas, being more active, is responsible for the
appearance of a strong fan. The other area, which is
far less active, generates a jet that manifests itself near
perihelion. The peak dust production of the comet
120–150 days before perihelion is due to the presence
of an active fan in the inner coma.