Burst of the 1969 Leonids and 1982 Lyrids

Radar observations of the last bursts of the Leonids in 1969 and Lyrids in 1982, carried out at the Springhill Meteor Observatory, Canada, both of very short duration, with the rates exceeding a quarter-maximum rate within 50-55 minutes, are used for a study of the mass distribution of meteoroids. In both cases the mass distribution exponents of the meteoroids in the dense clouds largely differ from the values obtained for the older populations of the streams. The highest mass exponent s approximately 2.2-2.4 is found around the peak of the activity, confirming high contribution of smaller meteoroids, and thus also a recent origin of the dense clouds. Consequences of these findings are discussed

Activity of the Lyrid meteor stream

The activity of the Lyrid meteor stream is in most years fairly low with a visual rate at maximum (21-22 April) of 5-10 meteors per hour. Short bursts of very high Lyrid activity, with visual hourly rates of 100 or more, have sometimes been reported. These observations generally refer to faint visual meteors. The reported bursts of high activity have occurred in a very narrow interval of solar longitudes (deg 31.24 to 31.38 equinox 1950.0), while the recurrent or 'normal' maximum for bright meteors occurs at solar longitude deg 31.6, or slightly later. A mass separation of the meteors in the shower is thus indicated

On associations of Apollo asteroids with meteor streams

Potential associations of Apollo asteroids with meteor streams are searched on the basis of the orbital parameters comparison. From all Apollo asteroids discovered through 1991 June those are only selected for further analysis whose orbits approach to less than 0.1 AU to the Earth's orbit. Their orbits are compared with precise photographic orbits of individual meteors from the Meteor Data Center in Lund. Results on the associations of asteroids with meteor streams are presented and discussed

Natural remanent magnetization of Rumanova chondrite (H5) acquired by the shock metamorphisms S3

The natural remanent magnetization (NRM) of Rumanova (H5) chondrite was studied to focus on the shock remagnetization characterized by shock level S3. The NRM was examined by AF and thermal demagnetization, temperature dependencies of magnetization and coercivity, magnetic anisotropy, microscopic features using magnetic fluid technique and chemical compositions. Based on these results, Rumanova carries the stable NRM by a fine-grained taenite with 48 wt% Ni in cloudy taenite, although large amount of the soft NRM component with the magnetic anisotropy is overprinted. These taenite grains were produced by disorder from tetrataenite due to heating between 525℃ and 950℃ during shock metamorphism when the parent body collided with the asteroids. Rumanova was remagnetized below 530℃ in the cooling stage by the local magnetic field from strongly magnetized FeNi grains. From these viewpoints, the NRM of Rumanova was not original, but it was remagnetized during shock metamorphism

The Updated IAU MDC Catalogue of Photographic Meteor Orbits

The database of photographic meteor orbits of the IAU Meteor Data Center at the Astronomical Institute SAS has gradually been updated. To the 2003 version of 4581 photographic orbits compiled from 17 different stations and obtained in the period 1936-1996, additional new 211 orbits compiled from 7 sources have been added. Thus, the updated version of the catalogue contains 4792 photographic orbits (equinox J2000.0) available either in two separate orbital and geophysical data files or a file with the merged data. All the updated files with relevant documentation are available at the web of the IAU Meteor Data Center. Keywords astronomical databases photographic meteor orbits 1 Introduction Meteoroid orbits are a basic tool for investigation of distribution and spatial structure of the meteoroid population in the close surroundings of the Earth s orbit. However, information about them is usually widely scattered in literature and often in publications with limited circulation. Therefore, the IAU Comm. 22 during the 1976 IAU General Assembly proposed to establish a meteor data center for collection of meteor orbits recorded by photographic and radio techniques. The decision was confirmed by the next IAU GA in 1982 and the data center was established (Lindblad, 1987). The purpose of the data center was to acquire, format, check and disseminate information on precise meteoroid orbits obtained by multi-station techniques and the database gradually extended as documented in previous reports on the activity of the Meteor Data Center by Lindblad (1987, 1995, 1999 and 2001) or Lindblad and Steel (1993). Up to present, the database consists of 4581 photographic meteor orbits (Lindblad et al., 2005), 63.330 radar determined orbit: Harvard Meteor Project (1961-1965, 1968-1969), Adelaide (1960-1961, 1968-1969), Kharkov (1975), Obninsk (1967-1968), Mogadish (1969-1970) and 1425 video-recordings (Lindblad, 1999) to which additional 817 video meteors orbits published by Koten el al. (2003) wer

Astrophysics in 2005

We bring you, as usual, the Sun and Moon and stars, plus some galaxies and a new section on astrobiology. Some highlights are short (the newly identified class of gamma-ray bursts, and the Deep Impact on Comet 9P/ Tempel 1), some long (the age of the universe, which will be found to have the Earth at its center), and a few metonymic, for instance the term "down-sizing" to describe the evolution of star formation rates with redshift

Orionid Meteor Stream

Based on data available at the IAU (International Astronomical Union) Meteor Data Center in Lund 60 precisely reduced photographic Orionid orbits and 17 video observed orbits are analysed. Mean photographic and video orbits are compared with the orbit of comet Halley. The Orionid meteoroid stream structure and radiant motion is studied, and compared with previous visual and photographic studies of the stream. Reports based on visual observations of a very complicated radiant structure of the Orionid stream are not substantiated