The relationship between color and polarization in comets: clues to understanding microphysical properties of cometary dust and mechanisms of its ejection
Program: GRANTS OF THE SLOVAK GRANT AGENCY APVV (APVV-19-0072)
Project leader: Mgr. Oleksandra Ivanova, PhD.
Duration: 1.7.2020-30.62024Abstract:The aim of the project focuses on the research of physical properties of dust particles in cometary atmospheres. For the first time, the systematic study of rapid changes in a color index and a degree of linear polarization of 10 comets (in minimum) will be performed, and this allow us to estimate the frequency of such phenomena in comets. The vast majority of comets were observed in a limited number of periods and/or with a long time intervals among them. However, taking into account the recent finding of rapid variations in cometary dust properties from the scattering of sunlight, it is a lack of agreement with observational results. Our research carried out within this project should help to resolve this very important issue. Characteristics of comets obtained from our observations, as well as already archived data, will be analyzed for the rate of change in a color index and/or in a degree of linear polarization in comet's coma and tail. This should allow us to find a correlation among observed color changes and polarization and the microphysical characteristics of cometary dust. In addition, a possible correlation of rapid color variations and polarization with other cometary characteristics such as their orbital motion, chemical composition of ice, thermal emissions, etc. will be examined. This analysis will improve our understanding of mechanisms that causes a rapid changes in comets and thus qualitatively improve our knowledge of short-term processes in cometary evolution.
Investigation of development of the physical activity of dynamical new comets over the wide range of heliocentric distances
Program: SASPRO, SAV (FP7 and Marie Curie Actions)
Project leader: Oleksandra Ivanova PhD.
Duration: 25.02.2016 - 31.12.2018Abstract:The main goal of the presented project is to study the physical properties of the atmospheres and tails in the dynamically new comets. The project is focused on the study of the evolution of physical activities of the comets depending on their distance from the Sun. The archived photometric, spectrophotometric, and polarimetric data, as well as the new observations of the comets at different heliocentric distances, will be used to solve this topic. Our objects are comets with a perihelion distance, q, in the range of 0.01 - 3 AU. In the first stage of the project, the observations of the selected comets (using different methods of observations) with higher activity at the large heliocentric distances (r>4 AU) will be presented. Here, we also include observational data, obtained by principal investigator (PI) of the presented project, based on the previous observations. In the second stage of project, the observations of new comets (with broadband filters (BVR), which will be active at large heliocentric distances (r>4 AU), will continue. We want to obtain further observations of the comets (with narrow band filters), which were observed at large heliocentric distances during the first stage of the project, but this time will be in a closer distance to the Sun (r<3 AU). In the final stage of the project, an analysis of the obtained spectroscopic, photometric and polarimetric data will be done: detection of gas emission, estimation of dust and gas productivity, morphology of dust and gas coma and estimation of the degree of polarization at large phase angles. We will construct light curves of the cometary brightness changes. Also, the estimations of refractive indexes, sizes and density of particles of comet dust will be done. To do these estimations, we use the photometric and spectropolarimetric observations and results of the measurements performed in space (taken from the literature) and based on a modelling.