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

Abstract

Observations of the comet werecarried out using the OMT-800 telescope (the primarymirror diameter D = 80 cm; the focal length F =214 cm) of the Odessa Observatory telescope networkfrom January to June 2020. Image processing was per-formed through standard methods using subtraction ofdark and flat field frames. The resulting frames wereemployed to analyse the morphology of the cometaryinner coma using digital filters. Isophotes of the comaand images of its structures appearing as fans and jetswere obtained. The presence of a strong fan, whichdistorts the coma’s standard appearance and makesit elongated perpendicularly to the Sun-comet line, isobserved over the period from January to April. Lateron, a weak jet that hardly affects the coma’s standardshape appears to replace the fan. The jet reaches itspeak intensity near perihelion and then gets fainterrapidly. Such behaviour of the coma structures isindicative of the presence of two active areas on thecometary nucleus surface, for which the matter outflowis governed by the Sun illumination conditions. Oneof these areas, being more active, is responsible for theappearance of a strong fan. The other area, which isfar less active, generates a jet that manifests itself nearperihelion. The peak dust production of the comet120–150 days before perihelion is due to the presenceof an active fan in the inner coma.