Stefan Gajdos

The Bologna-Modra forward-scatter radar experiment: reflection properties of meteor trains

Abstract Observational results on the reflection properties of meteor trains obtained by forward-scatter bistatic radar over the baseline Bologna Modra (about 700 km), as well as some characteristics of the Lyrid shower meteors in 1993, are presented here. The observations following the shower radiant motion showclearly that the orientation of the baseline of the forward-scatter system is the dominating factor affecting the flux of the recorded meteors. Even the long-enduring meteor trains which were proved to be independent in a backscatter system of the specular reflection conditions, are observed herewith to be strongly dependent on the baseline orientation with a maximum rate corresponding to the radiants having the baseline as azimuth.

KUIPER-BELT OBJECTS: DISTRIBUTION OF ORBITAL ELEMENTS AND OBSERVATIONAL SELECTION EFFECTS

The influence of the observational selection effects in the set of bodies known also as the Edgeworth-Kuiper belt objects (EKGs) is investigated. The most important observational selection effect is closely connected with the fact that precise orbits are known mainly for objects with smaller perihelion distance, discoveries of the objects were done i) near their orbital nodes, or, ii) objects with small inclinations are known. Distribution of EKOs in perihelion distance is not comparable with any known set of objects in the solar system. Mass index exhibits different values for the inner and outer zones of the known Edgeworth-Kuiper belt.

Observation of collision of comet Shoemaker-Levy 9 with Jupiter at the Astronomical and Geophysical Observatory in Modra

A report about observations of collision of the comet Shoemaker-Levy 9 with Jupiter is presented. The observations were made both in optical and radio wavelengths. Some consequences of impacts of individual fragments of the comet were detected visually in the 20-cm refractor. 21 days prolonged series of records on a video tape was taken in the focus of the 60-cm reflector, too. 13 serious events from July 16, 1994 to July 23, 1994 on 42.7 MHz radio wavelengths were registered. Its coherence with the pair Shoemaker-Levy 9 and Jupiter in the interaction is the subject of further investigation. More comprehensive results will be published after collecting information about similar observations on radio waves all over the world.

On the brightness of comet P/Halley in the past

Abstract This paper deals with the brightness changes of come P/Halley in the past. On the basis of the analysis of Sun-Earth-comet configuration at the time of perihelion passage within 30 apparitions of the comet since 240 BC, several groups of apparitions of similar observing geometry were specified. These groups were analysed with emphasis on brightness variations of the comet on different, long time scales. Absolute magnitudes and duration of naked-eye visibility both in pre-perihelion and post-perihelion periods of the comet are the main criteria for the aim of this study. Some brightness increase of the comet in 912–1222 is indicated.