Potential Draconid hunting will be entirely impractical this year, unless there is a strong outburst (none are predicted), thanks to full Moon on October 7. If anything were to occur from them, their possible past peak timings would span October 8, 14h30m UT (λ = 197°075, the equivalent 1998 outburst time) and 22h20m UT (the nodal crossing time, λ = 195°4), to October 9, 4h —7h UT (the equivalent 1999 minor outburst time, λ = 195°63 —195°76). Fortunately things improve substantially for the ε-Geminids and Orionids later in the month. November’s full Moon spoils the Southern Taurid peak on November 5, and even by the Northern branch’s maximum on November 12, the Moon will still be a problem for too much of the night. The October part of the potentially interesting late October to early November phase of the Taurids, which occasionally produces enhanced rates or more fireballs than usual, is favoured by a crescent to first quarter Moon at least. Later in November, the Leonids and α-Monocerotids have perfectly moonless skies. The early December mostly minor shower maxima are largely lost to the bright Moon, but this clears away for the Geminids, Coma Berenicids and Ursids. Peaks for the other December showers are: χ-Orionids — December 2; Phoenicids — December 6, 15h UT; Puppid-Velids — around December 7; Monocerotids — December 9; sigma-Hydrids — December 12.
ε-Geminids (EGE)
Active: October 14 —27; Maximum: October 18 (λ = 205°); ZHR = 2;
Radiant: α = 102°, δ = +27°; Radiant drift: see Table 6 (page 23);
v∞ = 70 km/s; r = 3.0;
TFC: α = 090°, δ = +20° and α = 125°, δ = +20° (β > 20° S).
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A weak minor shower with characteristics and activity nearly coincident with the Orionids, so great care must be taken to separate the two sources by instrumental techniques — especially video or telescopic work — or visual plotting. The waning crescent Moon will be only a minor distraction long after midnight, so this is a good opportunity to obtain more data on them from either hemisphere. Northern observers have a radiant elevation advantage which they can usefully access from about midnight onwards, but more southerly observers have a later moonrise.
Orionids (ORI)
Active: October 2 —November 7; Maximum: October 21 (λ = 208°); ZHR = 23;
Radiant: α = 095°, δ = +16°; Radiant drift: see Table 6 (page 23);
v∞ = 66 km/s; r = 2.5;
TFC: α = 100°, δ = +39° and α = 075°, δ = +24° (β > 40° N); or
α = 080°, δ = +01° and α = 117°, δ = +01° (β < 40° N).
October’s new Moon almost perfectly favours the Orionids at their peak. The shower’s radiant, near the celestial equator, is at a useful elevation by around local midnight in either hemisphere, somewhat before in the north, so most of the world can enjoy the shower. Audrius Dubietis carried out an analysis of the shower in IMO data from 1984 —2001 in early 2003, allowing some minor modifications to the peak ZHR and r parameters. Both these aspects were shown to vary somewhat from year to year, the maximum mean ZHR especially ranging from ~ 14 —31 during the examined interval. In addition, a suspected 12-year periodicity in higher returns found earlier in the 20th century appears to have been partly confirmed, which may mean stronger returns in 2008 —10, and perhaps best ZHRs around 20 —25 this year. The Orionids were always noted for having several lesser maxima other than the main one above, helping activity sometimes to remain roughly constant for several consecutive nights centred on this peak. In 1993 and 1998, a submaximum about as strong as the normal peak was detected on October 17 —18 from Europe, for instance. All observers should be aware of these possibilities, as observing circumstances are favourable for covering much of October 17 —18 in dark skies this year. Several visual subradiants were reported in the past, but recent video work suggests the radiant is far less complex; photographic, telescopic and video work to confirm this would be useful, as visual observers have clearly had problems with this shower’s radiant determination before.
Leonids (LEO)
Active: November 14 —21; Maximum: November 17, 20h50m UT (λ = 235°27), but see below; ZHR = 10 —100+?;
Radiant: α = 153°, δ = +22°; Radiant drift: see Table 6 (page 23);
v∞ = 71 km/s; r = 2.9;
TFC: α = 140°, δ = +35° and α = 129°, δ = +06° (β > 35° N); or
α = 156°, δ = -03° and α = 129°, δ = +06° (β < 35° N).
PFC: α = 120°, δ = +40° before 0h local time (β > 40° N);
α = 120°, δ = +20° before 4h local time and
α = 160°, δ = 00° after 4h local time (β > 00° N);
α = 120°, δ = +10° before 0h local time and α = 160°, δ = -10° (β < 00° N).
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As the events of 2003 and 2004 demonstrated, when enhanced ZHRs of ~ 20 —40 were found, the ending of the strong to storm Leonid returns between 1998 —2002, associated with the 1998 perihelion passage of parent comet 55P/Tempel-Tuttle, have not meant an end to interest in this fascinating shower. This year may bring a return to still higher Leonid activity, perhaps with ZHRs of 100 —150. The timing above is for the nodal crossing, and if recent past years are a guide, any associated activity near then may be swamped by other filaments within the stream. The prediction of higher (though not storm!) rates from the 1933 filament by Rob McNaught and David Asher is timed for November 19, 4h45m UT. More recent work by Esko Lyytinen and Tom van Flandern gave a fractionally different timing of 4h48m UT, which essentially confirmed the earlier findings. The Leonid radiant rises usefully only around local midnight (or indeed afterwards south of the equator), and with new Moon on November 20, dark skies should prevail almost all night for both potential maxima. A peak close to the nodal crossing time would favour sites across Asia, but the possibly enhanced maximum timing would be best for sites in eastern North America and all of South America eastwards to Africa and Europe. Other possible maxima are not excluded (look out for any late updates in WGN or on the IMO-News e-mailing list), and observers should be watching as often as conditions allow throughout the shower, in case something unexpected happens. All observing techniques can be usefully employed.
α-Monocerotids (AMO)
Active: November 15 —25; Maximum: November 21, 21h05m UT (λ = 239°32);
ZHR = variable, usually ~ 5, but may produce outbursts to ~ 400+;
Radiant: α = 117°, δ = +01°; Radiant drift: see Table 6 (page 23);
v∞ = 65 km/s; r = 2.4;
TFC: α = 115°, δ = +23° and α = 129°, δ = +20° (β > 20° N); or
α = 110°, δ = -27° and α = 098°, δ = +06° (β < 20° N).
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Another late-year shower capable of producing surprises, the α-Monocerotids gave their most recent brief outburst in 1995 (the top EZHR, ~ 420, lasted just five minutes; the entire outburst 30 minutes). Many observers across Europe witnessed it, and we were able to completely update the known shower parameters as a result. Whether this indicates the proposed ten-year periodicity in such returns is real or not is still unknown, as this was written before the 2005 decadal return. Whatever 2005 brought, all observers should continue to monitor this shower closely, in case of other unexpected events. New Moon on November 20 is excellent news for observers this year. The radiant is well on view from either hemisphere only after about 23h local time, so the peak timing would fall especially well for sites from eastern Europe and eastern Africa east across most of Asia.
Geminids (GEM)
Active: December 7 —17; Maximum: December 14, 10h45m UT (λ = 262°2) ± 2.3h;
ZHR = 120;
Radiant: α = 112°, δ = +33°; Radiant drift: see Table 6 (page 23);
v∞ = 35 km/s; r = 2.6;
TFC: α = 087°, δ = +20° and α = 135°, δ = +49° before 23h local time,
α = 087°, δ = +20° and α = 129°, δ = +20° after 23h local time (β > 40° N);
α = 120°, δ = -03° and α = 084°, δ = +10° (β < 40° N).
PFC: α = 150°, δ = +20° and α = 060°, δ = +40° (β > 20° N);
α = 135°, δ = -05° and α = 080°, δ = 00° (β < 20° N).
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One of the finest annual showers presently observable. This year, the waning crescent Moon rises within half an hour of 1h local time across the globe on December 14, but will be a fairly minor nuisance even so. There will be some useful dark-sky observing opportunities, especially from the northern hemisphere, as while the Geminid radiant culminates around 2h local time, well north of the equator it rises around sunset, and is at a usable elevation from the local evening hours onwards. In the southern hemisphere, the radiant appears only around local midnight or so, however. Even from more southerly sites, this is a splendid stream of often bright, medium-speed meteors, a rewarding sight for all watchers, whatever method they employ. The peak has shown slight signs of variability in its rates and timing in recent years, with the more reliably observed maxima during the past two decades all having occurred within 2h20m of the time given above. The main predicted timing favours places in the extreme Far East eastwards right across North and Central America particularly. An earlier or later timing would extend this best-visible zone some way eastwards or westwards respectively. Some mass-sorting within the stream means the fainter telescopic meteors should be most abundant almost 1° of solar longitude (about one day) ahead of the visual maximum, with telescopic results indicating these meteors radiate from an elongated region, perhaps with three sub-centres. Further results on this topic would be useful.
Coma Berenicids (COM)
Active: December 12 —January 23; Maximum: December 20 (λ = 268°); ZHR = 5;
Radiant: α = 175°, δ = +25°; Radiant drift: see Table 6 (page 23);
v∞ = 65 km/s; r = 3.0;
TFC: α = 180°, δ = +50° and α = 165°, δ = +20° before 3h local time,
α = 195°, δ = +10° and α = 200°, δ = +45° after 3h local time (β > 20° N).
[image:73]
A weak minor shower that is usually observed only during the Geminid and Quadrantid epochs, but which needs more coverage at other times too, especially to better define its maximum. The shower is almost unobservable from the southern hemisphere, so northern watchers must brave the winter cold to improve our knowledge of it. The radiant is at a useful elevation from local midnight onwards, and with a peak exactly at new Moon, conditions are perfect.
Ursids (URS)
Active: December 17 —26; Maximum: December 22, 19h UT (λ = 270°7);
ZHR = 10 (occasionally variable up to 50);
Radiant: α = 217°, δ = +76°; Radiant drift: see Table 6 (page 23);
v∞ = 33 km/s; r = 3.0;
TFC: α = 348°, δ = +75° and α = 131°, δ = +66° (β > 40° N);
α = 063°, δ = +84° and α = 156°, δ = +64° (β = 30° to 40° N).
A very poorly observed northern hemisphere shower, but one which has produced at least two major outbursts in the past 60 years, in 1945 and 1986. Several other rate enhancements, recently in 1988, 1994 and 2000, have been reported too. Other similar events could easily have been missed due to poor weather or too few observers active. All forms of observation can be used for the shower, since many of its meteors are faint, but with so little work carried out on the stream, it is impossible to be precise in making statements about it. The radio maximum in 1996 occurred around λ = 270°8, for instance, which might suggest a slightly later maximum time in 2006 of December 22, 21h30m UT, while the 2000 enhancement was seen surprisingly strongly (EZHR ~ 90) by video at λ = 270°78 (equivalent to 2006 December 22, 21h UT), although the visual enhancement was much less, ZHR ~ 30. The Ursid radiant is circumpolar from most northern sites (thus fails to rise for most southern ones), though it culminates after daybreak, and is highest in the sky later in the night. December’s new Moon creates ideal conditions for observing near the maximum. If they recur as suggested, the peak timings should favour northerly sites between Europe and Africa eastwards to the Far East.
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