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On 2013 December 9, the Central Bureau for Astronomical Telegrams (CBAT) issued a circular announcing that the Canadian Meteor Radar Orbit system had detected an outburst of Andromedid meteors. It was suggested that visual observers should go out and monitor the activity. Unfortunately no information was provided regarding the the size of the particles involved - this would have given an indication as to likely meteor magnitudes
The Andromedid meteor shower was associated with comet 3D/Biela which disintegrated over the course of the 19th century. The shower produced meteor storms on the nights of 1872 Nov 27 and 1885 Nov 27. However, the gravitational effects of the planets then pulled the meteor stream away from the Earth and so the shower ceased to occur. It is unclear as to how it was determined that the meteor outbursts seen this year (and another in 2011) were linked to the Andromedid shower. Previous studies had suggested that any future Andromedid activity would occur in mid November.
No activity was subsequently reported by visual observers. In addition, Alastair McBeath checked the recent Radio Meteor Observation Bulletins and they had revealed no unusual activity.
It was subsequently revealed that the radar activity had been detected during the night of Dec 6-7, rather than on Dec 9th when the circular was issued.
The likelihood is that the radar observations detected particles that were far too small to produce naked-eye meteors. Whether this shower was related in any way to the 19th century meteor shower remains to be seen.
The distribution of particle sizes varies from one meteor shower to another. Showers like the Perseids and Geminids are rich in "large" particles and so are rich in bright meteors. Other showers, such as the Delta Aquarids and Draconids are deficient in "large" particles and so produce few bright meteors. Some meteor showers contain virtually no particles large enough to produce naked-eye meteors - but they may be rich in the very small particles that produce radar activity. It may be that the reported shower falls into this latter category.
A live feed of the activity being detected by the Canadian Meteor Orbit Radar can be found at http://fireballs.ndc.nasa.gov/cmor-radiants/ . There is also a movie download (27MB) available that shows a year's worth of detected radar activity at http://meteor.uwo.ca/movies/year-slow.avi
Added by: Tracie Heywood