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PhD. Topics

Astronomical Institute

Short-term color changes in comets at large heliocentric distances
PhD. program
Astronomy and Astrophysics
Name of the supervisor
Mgr. Oleksandra Ivanova, PhD.
Receiving school
Faculty of Mathematics, Physics and Informatics
Focus of the research: Microphysical properties of dust particles in the vast majority of comets can be deduced only using remote-sensing techniques based on the interaction of dust with solar radiation. Such interaction is manifested in three sets of phenomena: the elastic scattering of the sunlight in visible and near-IR bands, thermal emission of the absorbed solar radiation in mid-IR, and the radiation pressure that affects the motion of dust particles and, their spatial distribution in the coma and tail.
Photometric colour of dust particles is defined as the ratio of scattered-radiation fluxes measured at two different wavelengths. Its strength lies in the relative nature as it depends directly on the microphysical properties of the dust particles, and it is independent of their number within the field of view. This is important because it is known that the number of dust particles forming a cometary coma is a subject to rapid and significant variations.
Main goal of the work is using long-lasting observations of selected distant comets searching for variations of its colour. Detecting of fast changes in colour of distant comets provides important clues for better understanding of the microphysical properties of its dust.
Methods: Photometry with broadband filters of selected distant comets. Studying fast variations of the color index in selected distant comets, searching for the frequency of occurrence of this phenomenon in various comets, its interrelation with other features of comets. Building the color maps of the comets. The use of the spectrum will provide exhaustive information on the presence of gaseous emissions in comets, which makes it very possible to derive the colour of cometary dust.

Requirements: knowledge of English language, good background in physics, basic knowledge in programing (IDL), ability to work independently with literature.

Affiliation: Astronomical Institute of the Slovak Academy of Sciences, The Department of Interplanetary Matter, Tatranska Lomnica

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