The waxing crescent Moon favours the Quadrantids in early January, while the waxing gibbous Moon still allows coverage near the probable α-Centaurid maximum in early February. Both the minor potential δ-Cancrid peak around January 11 and its more usually listed maximum on January 17 are lost to full Moon, but not so the δ-Leonids in late February. The diffuse ecliptical stream complex of the Virginids gets underway by late January, running through to mid April, probably producing several low, and poorly observed, maxima in March or early April. The interesting late January to early February spell has a waning Moon, which should cause only a few difficulties during most of the, perhaps core, January 20 —27 period. Mid-March sees the possible minor γ-Normid peaks around March 13 or 17 spoilt by the Moon. Theoretical approximate timings for the two daytime radio shower maxima this quarter are: Capricornids/Sagittarids — February 1, 14h UT; and χ-Capricornids — February 13, 15h UT. Recent radio results suggest the Cap/Sgr maximum may variably fall sometime between February 1 —4 however, while activity near the expected χ-Capricornid peak has tended to be slight and up to a day late. Both showers have radiants < 10° —15° west of the Sun at maximum, so cannot be regarded as visual targets even from the southern hemisphere. In addition to these known sources, there is a theoretical encounter with any dust-trail left by long-period comet Tago-Sato-Kosaka (C/1969T) close to 6h20m UT on January 2, suitable only for southern hemisphere observations. According to data published by Esko Lyytinen and Peter Jenniskens, the radiant should be in Norma (the nearest “bright” star is the 4th-magnitude β Circini, but α Centauri is only some 6° —7° away too), around α = 231°, δ = -57° at λ = 281°633. Activity is unknown, possibly none at all, but the miss distance between the Earth and the comet’s trail is very small, 0.00028 astronomical units inside the Earth’s orbit (about 42000 km). As usual in such cases, the theoretical radiant should be used only as a rough guide, and all potential meteors from this source plotted, or recorded by instrumental methods, for later analyses. Although circumpolar from latitude 35° S, the radiant area is best visible only well after local midnight. Helpfully, there is no Moon.
Quadrantids (QUA)
Active: January 1 —5; Maximum: January 3, 18h20m UT (λ = 283°16);
ZHR = 120 (can vary ~ 60 —200);
Radiant: α = 230°, δ = +49°; Radiant drift: see Table 6 (page 23);
v∞ = 41 km/s; r = 2.1 at maximum, but variable;
TFC: α = 242°, δ = +75° and α = 198°, δ = +40° (β > 40° N).
PFC: before 0h local time α = 150°, δ = +70°;
after 0h local time α = 180°, δ = +40° and
α = 240°, δ = +70° (β > 40° N).
A splendid return of the Quadrantids starts the northern observers’ year very well, with an expected peak around 18h20m UT on January 3/4. The waxing crescent Moon was new on 2005 December 31, and will set by mid-evening in early January, so producing no significant problems at all. From many northern locations, the shower’s radiant is circumpolar, in northern Boötes, but it attains a useful elevation only after local midnight, rising higher in the sky towards morning twilight. Consequently, east Asian to Far Eastern longitudes will be the most favoured places to catch the shower’s best, if the peak keeps to time. 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.
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The maximum time given above is based on the best-observed return of the shower ever analysed, in 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 1998 persisted for over two hours at their best. 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 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 2006 would fall ideally for sites in Europe, North Africa and the Near East.
Past observations have suggested the 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. Photographic and video observations from January 1 —5 would be particularly welcomed by those investigating this topic, using the PFCs and TFCs given above, along with telescopic and visual plotting results.
α-Centaurids (ACE)
Active: January 28 —February 21; Maximum: February 8, 5h UT (λ = 319°2);
ZHR = variable, usually ~ 6, but may reach 25+;
Radiant: α = 210°, δ = -59°; Radiant drift: see Table 6 (page 23);
v∞ = 56 km/s; r = 2.0.
In theory, the α-Centaurids are one of the main southern hemisphere high points in the opening months of the year, from past records supposedly producing many very bright, even fireball-class, objects (meteors of at least magnitude -3), commonly with fine persistent trains. Peak ZHRs, though normally listed as around 5 —10, have been suggested as much lower from the few sketchy reports made in more recent years. Then again, in 1974 and 1980, bursts of only a few hours’ duration yielded activity closer to 20 —30. As with many southern hemisphere sources, we have more questions than answers at present, nor do we have any means of telling when, or if, another stronger event might happen. Thus photographic, video and visual observers are urged to be alert at every opportunity. The radiant is nearly circumpolar for much of the sub-equatorial inhabited Earth, and is at a useful elevation from late evening onwards. Waxing gibbous moonset is around midnight to 1 a.m. local time this year, so providing one of those better chances to cover the shower, if skies stay clear.
δ-Leonids (DLE)
Active: February 15 —March 10; Maximum: February 24 (λ = 336°); ZHR = 2;
Radiant: α = 168°, δ = +16°; Radiant drift: see Table 6 (page 23);
v∞ = 23 km/s; r = 3.0;
TFC: α = 140°, δ = +37° and α = 151°, δ = +22° (β > 10° N);
α = 140°, δ = -10° and α = 160°, δ = 00° (β < 10° N).
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This minor shower is probably part of the early Virginid activity. Rates are normally low, and its meteors are predominantly faint, so it is a prime candidate for telescopic investigation. Visual observers must make very accurate plots of the meteors to distinguish them from the nearby Virginids and the sporadics. Northern hemisphere sites have an advantage for covering this stream, though southern hemisphere watchers should not ignore it, as they are better placed to note many of the other Virginid radiants. On the peak night, the waning crescent Moon rises in, or shortly before the start of, morning twilight for typical northern sites, but half an hour or so either side of 1h local time for most of the mid-southern hemisphere. In neither case will it be a serious distraction. The δ-Leonid radiant is well on view for most of the night then.