2012 Quadrantids

Completing the round-up of shower reports prior to my standing-down as SPA Meteor Director in 2012 April, we reach the 2012 Quadrantids.

Weather conditions were certainly kinder globally for this shower than others during the latter months of 2011, although the late-setting gibbous Moon restricted useful visual watching times quite considerably. UK observations were sadly few once again, and although support from the Section’s overseas contributors was excellent, the IMO’s visual dataset was of course much more complete even than these, and it is this which is used as the primary source of comparison information here. Two peaks were apparent in those results on January 4th, one around 05h-09h UT (average ZHRs ~ 80 ± 5), the other between roughly 17h-20:30 UT (average ZHRs ~ 75 ± 10), albeit the second maximum was based on a much smaller meteor sample. In between, and with a gap from about 14h-17h when no data were collected, activity seemed to have dropped to ~50 or so. There was also a drop to ZHRs of ~ 55 ± 10 in the hour centred at 07:40 UT during the first peak, although its significance was unclear as based on few meteors.

The IMO’s Quadrantid video observations featured in that Organization’s journal “WGN” 40:2 for 2012 April, pp. 76-79, notably pp. 76-77. These did not show a clear maximum at all, simply steeply rising rates overnight from Europe towards dawn on January 3-4. The estimated visual-ZHR-equivalent by circa 06h UT then was ~70. Unfortunately, no data were collected soon after the start of the following European night, thus no results were available to confirm the second IMO visual peak. Consequently, that feature has remained somewhat tentative.

Drawing on the radio results provided to the SPA, two main maxima were apparent on January 4th, from approximately 04h-06h and 11h-15h UT (recalling that the radio data are usually provided only in one-hour sampling intervals, so no greater temporal accuracy than to the nearest hour is possible). A much weaker possible third peak was found from 18h-20h UT or so, perhaps extending until 22h. The early part of the first radio maximum, through to the drop around 08h, mirrored the IMO visual findings fairly closely, but after that, the results diverged significantly, either in terms of peak timing for the second visual and radio maxima, or strength for the potential third event in both.

Careful checking of the data more closely suggested the second radio peak, though plausibly real, was perhaps of lesser significance than the first, as it happened at a time when the Quadrantid radiant was around its best-detectable from both the two main geographic observing regions, Europe and North America. The tertiary radio peak may similarly have been of somewhat more importance than its minor signature indicated, as it happened during the worst possible time for European observers, though all three maxima featured in data from both observing zones.

Quite why the visual and radio patterns were not closely identical after the first peak is uncertain. It is particularly curious the visual rates were not more impressive during the second radio maximum, as this was apparent in all the available, if limited, longer-duration radio echo data, which showed a distinct peak in the hour beginning at 12:00 UT, data which is generally supposed to be more representative of meteors that should be readily observed visually. The better-confirmed radio-visual “primary” peak was reasonably close to the predicted maximum time, at least!

The list of observers who contributed to this Quadrantid report can be found on the SPA Forum at :  forum.popastro.com/viewtopic.php

Alastair McBeath
Assistant Meteor Director, Society for Popular Astronomy

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