The orbit, structure and evolution of the Lyrid meteoroid stream

The orbit and structure of the Lyrid meteor stream based on photographic orbits available in the IAU Meteor database are investigated. Seventeen Lyrids were found in the database and the radiant and orbit of the stream were derived. In the stream three very distinct groups of orbits-short-period, longperiod and extreme (hyperbolic orbits), are separated. The mutual consistence of the groups is investigated by following the orbital evolution of individual meteors. The long-period group has the evolution almost identical with that of the parent comet C/1861 G1 Thatcher. The hyperbolic orbits are most probably the result of erroneous measurements.