Orionids and Eta Aquariids in the IAU MDC database

Abstract

The structure of the Orionids and the Eta Aquariids meteor streams was studied using the IAU MDC Photographic Orbits Database. Both the streams are associated with one of the most active comet known in the cometary population – 1P/Halley. The stream is therefore constantly supplemented by new particles, what creates conditions for a formation of a complex internal structure. We found that two frequency maxima of the photographic Orionids identified at the solar longitudes λ⊙=208.5° and λ⊙=210.5° coincide with the positions of the maximum activity of the visual meteors and bolides. One of five identified associations (O1) probably does not belong to the Orionids, i.e. meteor stream 008 ORI, but regards the September omicron Orionids - 479 SOO. The orbital parameters of the filament O4 correspond to the mean orbit of the Orionids resulting from the meteor radar observations in the period 2002–2012. There is no spatial relation between meteors observed in May (031 ETA) and October (008 ORI). While Eta Aquariids are in fact the core of the stream, the orbits of Orionids are much further from the cometary orbit.