Enhanced Perseid meteor activity observed

2016 September 24

John W. Mason

The annual Perseid meteor shower is one of the most reliable of the year, with an average peak ZHR (Zenithal Hourly Rate) of 80-100m/h, but significant variations in maximum activity do occur from one year to the next. For the Perseids, enhanced activity may be caused by an encounter with a young dust trail laid down by the parent comet, 109P/Swift-Tuttle, at a previous return, and/or gravitational perturbations by one of the planets, particularly Jupiter, which shift the centre of the main stream so the Earth passes through regions where the dust grains are more densely concentrated.
In 2004, an encounter with the 1862 (1-rev) dust trail at a distance of 0.00132 au (12 years after the comet’s most recent return to perihelion) caused a 2-hour enhancement in Perseid rates with a peak ZHR of ~200 m/h, but consisting mainly of faint meteors. A similar encounter yielded a slight enhancement in Perseid rates in 2015 August, but modelling of the stream by various workers had indicated that the effects would probably be more marked in 2016 and 2017. In addition to encounters with both the 1-rev and 7-rev dust trails, it was considered likely that overall Perseid activity in 2016 could be enhanced due to a favourable gravitational perturbation by Jupiter. With the usual annual peak expected on August 12 between about 12:30 UT and 14:30 UT, during daylight hours from the UK, any enhanced activity due to the encounters with young dust trails had been predicted for the previous night, August 11/12.

Visual observations
Observations were still coming in as this issue of the Journal went to press, from observers using a wide range of observing techniques, so this is only a very preliminary summary of what occurred…. (continued)

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