Quadrantids (QUA) | | | Active: | January 1-5 | | Maximum: | January 3 12h50m UT (λo = 283°16) | | ZHR = | 120 (can vary ~ 60-200) | | Radiant: | α = 230° δ = +49° | | Radiant drift: | see Table 6 | | v∞ = | 41 km/s; r = 2.1 at maximum (but variable) | | TFC: | α = 242° δ = +75° and α = 198° δ = +40° (β > 40° N) | | IFC: | before 0h local time α = 150° δ = +70° | | ∞ after 0h local time α = 180° δ = +40° and α = 240° δ = +70° (β > 40° N) |
The waxing crescent Moon will set near local midnight for the maximum of the Quadrantids at northern hemisphere sites, from many of which, the shower's radiant is circumpolar, in northern Boötes. As this area attains a useful elevation only after local midnight, rising higher in the sky towards morning twilight, this is excellent news. However, the expected peak's timing falls poorly for land-based observers, except for those in the extreme western areas of North America, on islands in the North Pacific Ocean, and the extreme east of Russia. An interesting challenge is to try spotting the occasional long-pathed shower member from the southern hemisphere around dawn, but sensible Quadrantid watching cannot be carried out from such places.
The maximum timing above is based on the best-observed return of the shower ever analysed, from IMO 1992 data, confirmed by radio results in most years since 1996. The peak itself is normally short-lived, and can be easily missed in just a few hours of poor northern-winter weather, which may be why the ZHR level apparently fluctuates from year to year, but some genuine variability is probably present too. For instance, visual ZHRs in preliminary results from 2008 persisted for more than two hours at close to their best, with the maximum itself centred around three to four hours later than anticipated. An added level of complexity comes from the fact that mass-sorting of particles across the meteoroid stream may make fainter objects (radio and telescopic meteors) reach maximum up to 14 hours before the brighter (visual and photographic) ones, so observers should be alert throughout the shower. A few, but apparently not all, years since 2000 seem to have produced a, primarily radio, maximum following the main visual one by some 9-12 hours. Visual confirmation of any repeat near this time in 2009 would fall ideally for sites from Europe east to central Asia. Oddly, in 2008, there seemed to be two possible radio Quadrantid peaks, but the first was apparently about six hours before the visual one, during an apparent rates-plateau ahead of the main maximum in the visual data.
Past observations have suggested the QUA radiant is diffuse away from the maximum, contracting notably during the peak itself, although this may be a result of the very low activity outside the hours near maximum. Still-imaging and video observations from January 1-5 would be particularly welcomed by those investigating this topic, using the IFCs and TFCs given above, along with telescopic and visual plotting results. |
|
置顶卡
变色卡
千斤顶
显身卡
