THE COMETARY OUTBURSTS AT LARGE HELIOCENTRIC DISTANCES

A model is presented explaining changes in cometary brightness during an outburst at large heliocentric distances. It is shown that a combin ation of the following effects can explain the main characteristics of outburst at large heliocentric distances: the specific exothermic pro cesses in cometary nucleus (as the HCN polymerisation and the crystall ization of the water amorphous ice, connected with the ejection of the large quantities of dust) and the sublimation of CO or CO2 from the c omet's nucleus. The obtained results are in good agreement with observ ations.