The age of the Orionid meteoroid stream

Abstract
The age of the Orionid meteoroid stream is estimated from the ratio of the mass of the stream to that of Halley's comet. A number of measurements spanning a range of about 5 visual magnitudes of the flux of meteoroids from radar, low-light-level TV and visual observations of the Orionid meteor shower have been used to determine the cumulative zenithal flux as a function of meteoroid mass. The different sets of observational data show a high degree of consistency. We have combined the flux data with McIntosh & Hajduk's ribbon model of the stream to get a measure of the total mass of dust ejected by the comet. Comparison of this figure with the observations of Comet P/Halley from space probes indicates that the age of the stream lies in the range 2.5 × 103 to 6.2 × 104 yr with the most probable age being 2.3 × 104 yr. Our value for the stream age agrees well with that extrapolated by Yeomans (1986) for the time of the last close approach of Comet P/Halley to Jupiter.

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