2008年重要流星雨时间表
2008.1.3（ZHR=100） 象限仪座流星雨（牧夫座流星雨） 辐射点在子夜从东北升起2008.4.22（ZHR=20）天琴座流星雨 辐射点在22时左右从东北升起
2008.5.6（ZHR=30）南宝瓶座d（德尔塔）流星雨 3时左右流星雨从东南升起
2008.8.13（ZHR=100） 英仙座流星雨 22时辐射点从东北升起
2008.9.1（ZHR=15） 御夫座流星雨 23时辐射点从东北升起
2008.11.17（ZHR不确定，可能只有十几） 狮子座流星雨，辐射点在子夜从东方升起
2008.12.13（ZHR=120） 双子座流星雨，辐射点在天黑后出现在东方地平线
2008.12.28(ZHR不定，可能会有十几） 小熊座流星雨 辐射点在北天极附近
Details in this Table were correct according to the best information available in May 2007, with maximum dates accurate only for 2008. Except for the two Antihelion Source line, all other showers are listed in order of their maximum solar longitude. An asterisk ('*') in the 'Shower' column indicates that source may have additional peak times, as noted in the text above. The parenthesized maximum date for the Puppids-Velids indicates a reference date for the radiant only, not necessarily a true maximum. Some showers have ZHRs that vary from year to year. The most recent reliable figure is given here, except for possibly periodic showers. These are either noted as 'Var' = variable, where there is considerable uncertainty over the likely maximum rates, or with an asterisk to indicate the value is that suggested from theoretical considerations for the current year.
[table][tr][td]Shower [/td][td]Activity [/td][td]Max Date [/td][td]λsol[/td][td]α [/td][td]δ [/td][td]vinf[/td][td][i]r[/i][/td][td]ZHR[/td][/tr][tr][td]Antihelion Source (ANT) [/td][td]Nov 26 - Sep 24 [/td][td][/td][td][/td][td][/td][td][/td][td]30 [/td][td]3.0 [/td][td] 3 [/td][/tr][tr][td]Quadrantids (QUA) [/td][td]Jan 01 - Jan 05 [/td][td]Jan 04 [/td][td]283°16 [/td][td]230° [/td][td]+49° [/td][td]41 [/td][td]2.1 [/td][td]120[/td][/tr][tr][td]α-Centaurids (ACE) [/td][td]Jan 28 - Feb 21 [/td][td]Feb 08 [/td][td]319°2 [/td][td]211° [/td][td]-59° [/td][td]56 [/td][td]2.0 [/td][td] 5[/td][/tr][tr][td]δ-Leonids (DLE) [/td][td]Feb 15 - Mar 10 [/td][td]Feb 25 [/td][td]336° [/td][td]168° [/td][td]+16° [/td][td]23 [/td][td]3.0 [/td][td] 2[/td][/tr][tr][td]γ-Normids (GNO) [/td][td]Feb 25 - Mar 22 [/td][td]Mar 13 [/td][td]353° [/td][td]239° [/td][td]-50° [/td][td]56 [/td][td]2.4 [/td][td] 4[/td][/tr][tr][td]Lyrids (LYR) [/td][td]Apr 16 - Apr 25 [/td][td]Apr 22 [/td][td] 32°32 [/td][td]271° [/td][td]+34° [/td][td]49 [/td][td]2.1 [/td][td] 18[/td][/tr][tr][td]π-Puppids (PPU) [/td][td]Apr 15 - Apr 28 [/td][td]Apr 23 [/td][td] 33°5 [/td][td]110° [/td][td]-45° [/td][td]18 [/td][td]2.0 [/td][td]Var [/td][/tr][tr][td]η-Aquariids (ETA) [/td][td]Apr 19 - May 28 [/td][td]May 05 [/td][td] 45°5 [/td][td]338° [/td][td]-01° [/td][td]66 [/td][td]2.4 [/td][td] 70+*[/td][/tr][tr][td]η-Lyrids (ELY) [/td][td]May 03 - May 12 [/td][td]May 08 [/td][td] 48°4 [/td][td]287° [/td][td]+44° [/td][td]44 [/td][td]3.0 [/td][td] 3[/td][/tr][tr][td]June Bootids (JBO) [/td][td]Jun 22 - Jul 02 [/td][td]Jun 27 [/td][td] 95°7 [/td][td]224° [/td][td]+48° [/td][td]18 [/td][td]2.2 [/td][td]Var [/td][/tr][tr][td]Piscis Austrinids (PAU) [/td][td]Jul 15 - Aug 10 [/td][td]Jul 27 [/td][td]125° [/td][td]341° [/td][td]-30° [/td][td]35 [/td][td]3.2 [/td][td] 5[/td][/tr][tr][td]South. δ-Aquariids (SDA) [/td][td]Jul 12 - Aug 19 [/td][td]Jul 27 [/td][td]125° [/td][td]339° [/td][td]-16° [/td][td]41 [/td][td]3.2 [/td][td] 20[/td][/tr][tr][td]α-Capricornids (CAP) [/td][td]Jul 03 - Aug 15 [/td][td]Jul 29 [/td][td]127° [/td][td]307° [/td][td]-10° [/td][td]23 [/td][td]2.5 [/td][td] 4[/td][/tr][tr][td]Perseids (PER)* [/td][td]Jul 17 - Aug 24 [/td][td]Aug 12 [/td][td]140°0 [/td][td] 46° [/td][td]+58° [/td][td]59 [/td][td]2.6 [/td][td]100[/td][/tr][tr][td]κ-Cygnids (KCG) [/td][td]Aug 03 - Aug 25 [/td][td]Aug 17 [/td][td]145° [/td][td]286° [/td][td]+59° [/td][td]25 [/td][td]3.0 [/td][td] 3[/td][/tr][tr][td]α-Aurigids (AUR) [/td][td]Aug 25 - Sep 08 [/td][td]Aug 31 [/td][td]158°6 [/td][td] 84° [/td][td]+42° [/td][td]66 [/td][td]2.6 [/td][td] 7[/td][/tr][tr][td]September Perseids (SPE) [/td][td]Sep 05 - Sep 17 [/td][td]Sep 09 [/td][td]166°7 [/td][td] 60° [/td][td]+47° [/td][td]64 [/td][td]2.9 [/td][td] 5[/td][/tr][tr][td]δ-Aurigids (DAU) [/td][td]Sep 18 - Oct 10 [/td][td]Oct 03 [/td][td]191° [/td][td] 88° [/td][td]+49° [/td][td]64 [/td][td]2.9 [/td][td] 3[/td][/tr][tr][td]Draconids (GIA) [/td][td]Oct 06 - Oct 10 [/td][td]Oct 08 [/td][td]195°4 [/td][td]262° [/td][td]+54° [/td][td]20 [/td][td]2.6 [/td][td]Var [/td][/tr][tr][td]ε-Geminids (EGE) [/td][td]Oct 14 - Oct 27 [/td][td]Oct 18 [/td][td]205° [/td][td]102° [/td][td]+27° [/td][td]70 [/td][td]3.0 [/td][td] 2[/td][/tr][tr][td]Orionids (ORI) [/td][td]Oct 02 - Nov 07 [/td][td]Oct 21 [/td][td]208° [/td][td] 95° [/td][td]+16° [/td][td]66 [/td][td]2.5 [/td][td] 30*[/td][/tr][tr][td]Leo Minorids (LMI) [/td][td]Oct 19 - Oct 27 [/td][td]Oct 24 [/td][td]211° [/td][td]162° [/td][td]+37° [/td][td]62 [/td][td]3.0 [/td][td] 2[/td][/tr][tr][td]Southern Taurids (STA) [/td][td]Sep 25 - Nov 25 [/td][td]Nov 05 [/td][td]223° [/td][td] 52° [/td][td]+15° [/td][td]27 [/td][td]2.3 [/td][td] 5[/td][/tr][tr][td]Northern Taurids (NTA) [/td][td]Sep 25 - Nov 25 [/td][td]Nov 12 [/td][td]230° [/td][td] 58° [/td][td]+22° [/td][td]29 [/td][td]2.3 [/td][td] 5[/td][/tr][tr][td]Leonids (LEO) [/td][td]Nov 10 - Nov 23 [/td][td]Nov 17 [/td][td]235°27 [/td][td]153° [/td][td]+22° [/td][td]71 [/td][td]2.5 [/td][td]20+*[/td][/tr][tr][td]α-Monocerotids (AMO) [/td][td]Nov 15 - Nov 25 [/td][td]Nov 21 [/td][td]239°32 [/td][td]117° [/td][td]+01° [/td][td]65 [/td][td]2.4 [/td][td]Var [/td][/tr][tr][td]Dec Phoenicids (PHO) [/td][td]Nov 28 - Dec 09 [/td][td]Dec 06 [/td][td]254°25 [/td][td] 18° [/td][td]-53° [/td][td]18 [/td][td]2.8 [/td][td]Var [/td][/tr][tr][td]Puppid/Velids (PUP) [/td][td]Dec 01 - Dec 15 [/td][td](Dec 06) [/td][td](255°) [/td][td]123° [/td][td]-45° [/td][td]40 [/td][td]2.9 [/td][td] 10[/td][/tr][tr][td]Monocerotids (MON) [/td][td]Nov 27 - Dec 17 [/td][td]Dec 08 [/td][td]257° [/td][td]100° [/td][td]+08° [/td][td]42 [/td][td]3.0 [/td][td] 2[/td][/tr][tr][td]σ-Hydrids (HYD) [/td][td]Dec 03 - Dec 15 [/td][td]Dec 11 [/td][td]260° [/td][td]127° [/td][td]+02° [/td][td]58 [/td][td]3.0 [/td][td] 3[/td][/tr][tr][td]Geminids (GEM) [/td][td]Dec 07 - Dec 17 [/td][td]Dec 13 [/td][td]262°2 [/td][td]112° [/td][td]+33° [/td][td]35 [/td][td]2.6 [/td][td]120[/td][/tr][tr][td]Coma Berenicids (COM) [/td][td]Dec 12 - Jan 23 [/td][td]Dec 20 [/td][td]268° [/td][td]177° [/td][td]+25° [/td][td]65 [/td][td]3.0 [/td][td] 5[/td][/tr][tr][td]Ursids (URS) [/td][td]Dec 17 - Dec 26 [/td][td]Dec 22 [/td][td]270°7 [/td][td]217° [/td][td]+76° [/td][td]33 [/td][td]3.0 [/td][td] 10[/td][/tr][/table] 国际流星雨组织预报（imo）
January to MarchA waning crescent Moon favours the northern-hemisphere Quadrantids in early January, while the new Moon is still better for the probable southern-hemisphere α-Centaurid peak in February. Mid-March brings a reasonable to very good minor γ-Normid return too, for similarly southern places. The Antihelion Source's radiant centre starts January in south-east Gemini, and crosses Cancer during much of the month, before passing into southern Leo for most of February. It then slips through southern Virgo during March. Likely ANT ZHRs will be <2, though IMO analyses suggest there may be an ill-defined minor peak with ZHRs ~ 2 to 3 around solar longitude ~ 286° — 293° (January 7 to 14 in 2008, well-timed for the new and waxing crescent Moon, if so), and ZHRs could be ~ 3 for most of March. The late January to early February spell, during which several new, swift-meteor, minor showers, radiating from the Coma-Leo-Virgo area have been suggested in some recent years, unfortunately has a full Moon for the potential core period, January 20 — 27. Theoretical approximate timings (rounded to the nearest hour) for the daytime radio shower maxima this quarter are: Capricornids/Sagittarids — February 2, 03h UT; and χ-Capricornids — February 14, 04h 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.
[img]http://www.imo.net/galleries/calendar/ant_8new.png[/img] [img]http://www.imo.net/galleries/calendar/ant_5new.png[/img] Quadrantids (QUA)[table][tr][td][/td][td][/td][/tr][tr][td]Active:[/td][td]January 1 — 5[/td][/tr][tr][td]Maximum:[/td][td]January 4 - 06h40m UT (λsol = 283°16)[/td][/tr][tr][td]ZHR = [/td][td]120 (can vary ~ 60 — 200)[/td][/tr][tr][td]Radiant:[/td][td]α = 230°; δ = +49°[/td][/tr][tr][td]Radiant drift:[/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]41 km/s; r = 2.1 at maximum but variable[/td][/tr][tr][td]TFC: [/td][td]α = 242°; δ = +75° and α = 198°; δ = +40° (β > 40° N)[/td][/tr][tr][td]IFC: [/td][td]before 0h local time α = 150°; δ = +70°[/td][/tr][tr][td][/td][td]after 0h local time α = 180°; δ = +40° and[/td][/tr][tr][td][/td][td]α = 240°; δ = +70° (β > 40° N)[/td][/tr][/table]
[img]http://www.imo.net/galleries/calendar/qua.png[/img] A virtually moonless maximum of the Quadrantids opens the northern meteor watchers' year very well, with a waning crescent Moon, four days from new, which rises only around or after 04h at mid northern latitudes, so it will be little nuisance. 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, eastern North American longitudes east to those of extreme western Europe and North Africa 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.
The maximum timing given 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 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 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 2008 would fall ideally for sites from East Asia east to sites around the eastern North Pacific Ocean.
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.
α-Centaurids (ACE)[table][tr][td][/td][td][/td][/tr][tr][td]Active:[/td][td]January 28 — February 21[/td][/tr][tr][td]Maximum:[/td][td]February 8 17h UT (λsol = 319°2)[/td][/tr][tr][td]ZHR = [/td][td]variable; usually ~ 5 but may reach 25+[/td][/tr][tr][td]Radiant: [/td][td]α = 211° δ = -59°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]56 km/s; [i]r[/i] = 2.0[/td][/tr][/table]
[img]http://www.imo.net/galleries/calendar/ace.png[/img]In theory, the α-Centaurids are one of the main southern summer high points, from past records supposedly producing many very bright, even fireball-class, objects (meteors of at least magnitude -3), commonly with fine persistent trains. However, peak ZHRs recently have been found as 5 or less in the few sketchy reports available, though in 1974 and 1980, bursts of only a few hours' duration apparently 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 imaging 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. New Moon falls almost perfectly for the predicted peak, an ideal chance for anyone favoured by clearer skies.
γ-Normids (GNO)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]February 25 — March 22[/td][/tr][tr][td]Maximum: [/td][td]March 13 (λsol = 353°)[/td][/tr][tr][td]ZHR = [/td][td]4[/td][/tr][tr][td]Radiant: [/td][td]α = 239° δ = -50°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]56 km/s; [i]r[/i] = 2.4[/td][/tr][tr][td]TFC: [/td][td]α = 225° δ = -26° and α = 215° δ = -45° (β < 15° S)[/td][/tr][/table]
γ-Normid meteors seem to be similar to the sporadics in appearance, and for most of their activity period, their ZHR is virtually undetectable above this background rate. The peak itself has been reported as quite sharp, with ZHRs of 3 to 4 often noted for only a day or two to either side of the maximum. Activity may vary somewhat at times, with occasional broader, or less obvious, maxima having been noted in the past. Limited data since 1999 have suggested the possibility of a maximum at some, albeit short-lived, stage between λsol ~ 350° — 357°, equivalent to 2008 March 10 — 17, while video information from the same period found the earlier radiant position to be no longer applicable. The details given here are now to be preferred. Post-midnight watching yields best results, when the radiant is rising to a reasonable elevation from southern hemisphere sites (the radiant does not rise for many northern ones). The shower badly needs more regular observation, and March's waxing Moon, at first quarter on March 14, means 2008 would be an excellent year to start. All observing techniques can be employed.
[img]http://www.imo.net/galleries/calendar/gno08.png[/img]April to JuneMeteor activity picks up towards the April-May boundary, with badly moonlit shower peaks in late April from the Lyrids (between 21h UT on April 21 to 08h UT on April 22, with probably better rates the closer the peak falls to ~ 05h UT on April 22) and π-Puppids (but see below), then the perfectly moonless η-Aquariids in early May, followed a few days later by a new Working List minor shower, the η-Lyrids. Later in May and throughout June, most of the meteor action switches to the day sky, with six shower maxima expected during this time. Although occasional meteors from the o-Cetids and Arietids have been claimed as seen from tropical and southern hemisphere sites visually in past years, ZHRs cannot be sensibly calculated from such observations. For radio observers, the theoretical UT peaks for these showers are as follows: April Piscids — April 20, 03h; δ-Piscids — April 24, 03h; ε-Arietids — May 9, 02h; May Arietids — May 16, 03h; o-Cetids — May 20, 01h; Arietids — June 7, 05h; ζ-Perseids — June 9, 04h; β-Taurids — June 28, 04h. Signs of most of these were found in radio data from 1994 — 2007, though some are difficult to define individually because of their proximity to other radiants. There seems to be a modest recurring peak around April 24, perhaps due to combined rates from the first three showers listed here, for instance, while the Arietid and ζ-Perseid maxima tend to blend into one another, producing a strong radio signature for several days in early to mid June. There are indications these two June shower maxima now each occur up to a day later than indicated above. The Antihelion Source should be relatively strong, with ZHRs of 3 to 4 found in recent investigations through till mid April, and again around late April to early May, late May to early June, and late June to early July. At other times, the ZHR seems to be below ~ 2 to 3. The radiant area drifts from south-east Virgo through Libra in April, then across the northern part of Scorpius to southern Ophiuchus in May, and on into Sagittarius for much of June. For northern observers, circumstances for checking on any potential June Lyrids (not currently on the Working List, but possibly producing some weak activity, if at all, around June 15) are very unfavourable this year, with a waxing gibbous Moon visible virtually all night then for most mid latitude sites. Conditions are much better for possible June Boötid hunting.
[img]http://www.imo.net/galleries/calendar/ant_9new.png[/img]π—Puppids (PPU)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]April 15 — 28[/td][/tr][tr][td]Maximum: [/td][td]April 23 10h UT (λsol = 33°5 — but see below)[/td][/tr][tr][td]ZHR = [/td][td]periodic - up to around 40[/td][/tr][tr][td]Radiant: [/td][td]α = 110° δ = -45°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]18 km/s [i]r[/i] = 2.0[/td][/tr][tr][td]TFC: [/td][td]α = 135° δ = -55° and α = 105° δ = -25° (β < 20° N)[/td][/tr][/table]
Despite the very poor lunar circumstances for observing this shower in 2008, we urge all who can to do so, because this is a young stream produced by Comet 26P/Grigg-Skjellerup, and the comet is at perihelion on 2008 March 23, just a month before the Earth passes nearest to the stream orbit. Activity has only been detected from this source since 1972, with notable, short-lived, shower maxima of around 40 meteors per hour found in 1977 and 1982, both years when the parent comet was at perihelion. Before 1982, little activity had been seen at other times, but in 1983, a ZHR of ~ 13 was reported, perhaps suggesting material has begun to spread further along the comet's orbit, as theory predicts. Comet Grigg-Skjellerup's perihelion in 2002 November produced nothing meteorically significant the following April, but this time's closer approach may yield something more interesting. There are no guarantees of course, but even registering a negative return this year would be valuable information, and regular monitoring of the shower epoch generally is vital, as past coverage has commonly been patchy, so other short-lived maxima could have been missed. Apart from the timing suggested above, Jérémie Vaubaillon has found three stream trails may pass close enough to the Earth to produce some activity, though these seem likely to consist of small particles only, perhaps producing meteors too faint for visual observation. The three trails were laid down in 1937, 1942 and 1947, and should be encountered between ~ 22h50m — 23h20m UT on April 22. The ZHR from each component may be ~ 10, ~ 4 and ~ 10 respectively, albeit possibly only for radio observers, unless we are fortunate.
[img]http://www.imo.net/galleries/calendar/ppu.png[/img]The π-Puppids are best-seen from the southern hemisphere, with useful observations mainly practical there before midnight, as the radiant is very low to setting after 01h local time. Even on April 23, the waning gibbous Moon will rise about as astronomical twilight is ending from mid-southern latitudes, thus the dark-sky observing window is virtually nil. Covering whatever happens is important however, so visual watchers must just make the best of things, and face away from the Moon, and not too close to the radiant, if clear skies manifest. Sites best-placed to catch the predicted maxima timings, if they prove accurate, should be from east Brazil east to Africa on April 22, and across the southern Pacific Ocean, including the eastern one-third of Australia and all of New Zealand on April 23. So far, visual and radio data have been collected on the shower, but the slow, sometimes bright nature of the meteors makes them ideal subjects for imaging too. No telescopic or video data have been reported in any detail as yet.
η-Aquariids (ETA)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]April 19 — May 28[/td][/tr][tr][td]Maximum: [/td][td]May 5 18h UT (λsol = 45°5)[/td][/tr][tr][td]ZHR = [/td][td]70+ (periodically variable ~ 40 — 85)[/td][/tr][tr][td]Radiant: [/td][td]α = 338° δ = -01°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]66 km/s; [i]r[/i] = 2.4[/td][/tr][tr][td]TFC: [/td][td]α = 319° δ = +10° and α = 321° δ = -23° (β < 20° S)[/td][/tr][/table]
A fine, rich stream associated with Comet 1P/Halley, like the Orionids of October, but one visible for only a few hours before dawn, essentially from tropical and southern hemisphere sites. Some useful results have come even from sites around 40° N latitude in recent years however, and occasional meteors have been reported from further north, but the shower would benefit from increased observer activity generally. The fast and often bright meteors make the wait for radiant-rise worthwhile, and many events leave glowing persistent trains after them. While the radiant is still low, η-Aquariids tend to have very long paths, which can mean observers underestimate the angular speeds of the meteors, so extra care is needed when making such reports.
A relatively broad maximum, sometimes with a variable number of submaxima, usually occurs in early May. Fresh IMO analyses in recent years, based on data collected between 1984 — 2001, have shown that ZHRs are generally above 30 between about May 3 — 10, and that the peak rates appear to be variable on a roughly 12-year timescale. The next highest rates should fall towards 2008 — 2010, if this Jupiter-influenced cycle is borne-out, thus ZHRs should be around 70 or more in 2008, according to this idea. The unexpectedly strong Orionid return of 2006 October adds a degree of extra uncertainty over what may be possible from this shower too, and new Moon on May 5 makes this a perfect year for checking. A more recent analysis of IMO video results has led to a slight amendment in the radiant drift, though the radiant at maximum is unchanged. All forms of observing can be used to study the shower, with radio work allowing activity to be followed even from many northern latitude sites throughout the daylight morning hours. The radiant culminates at about 8h local time.
[img]http://www.imo.net/galleries/calendar/eta08.png[/img]ε-Lyrids (ELY)[tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]May 3 — 12[/td][/tr][tr][td]Maximum: [/td][td]May 8 18h UT (λsol = 48°4)[/td][/tr][tr][td]ZHR = [/td][td]3[/td][/tr][tr][td]Radiant: [/td][td]α = 287° δ = +44°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]44 km/s; [i]r[/i] = 3.0[/td][/tr][tr][td]TFC: [/td][td]α = 325° δ = +40° or α = 285° δ = +15° and[/td][/tr][tr][td][/td][td]α = 260° δ = +30° (β > 10° S)[/td][/tr][/table]
This new introduction to the Working List is associated with Comet C/1983 H1 IRAS-Araki-Alcock, though it appears to be only a weak meteoric source. Most of the observational data on it so far has been based on imaging results. The radiant position is likely to be somewhere near the point given above at the presumed maximum, but may be some degrees from it. Recent IMO video results found a radiant centred near α = 290°, δ = +42°, for example, so other than video work careful visual or telescopic plotting will be needed to separate any potential ε-Lyrids from the sporadics. The radiant drift remains unmeasured, but was supposed to be 1° parallel to the ecliptic. The proposed radiant area is usefully on-view all night from the northern hemisphere (primarily), and the thin waxing crescent Moon will be setting by midnight for mid-northern latitudes on May 8, so will not be a significant problem for checking on any possible activity.
[img]http://www.imo.net/galleries/calendar/ely08.png[/img]June Boötids (JBO)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]June 22 — July 2[/td][/tr][tr][td]Maximum: [/td][td]June 27 02h30m UT (λsol = 95°7)[/td][/tr][tr][td]ZHR = [/td][td]variable: 0 — 100+[/td][/tr][tr][td]Radiant: [/td][td]α = 224° δ = +48°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]18 km/s; [i]r[/i] = 2.2[/td][/tr][tr][td]TFC: [/td][td]α = 156° δ = +64° and α = 289° δ = +67° (β = 25° — 60° N)[/td][/tr][/table]
[img]http://www.imo.net/galleries/calendar/jbo.png[/img]This source was reinstated on the Working List after its unexpected return of 1998, when ZHRs of 50 — 100+ were visible for more than half a day. Another outburst of similar length, but with ZHRs of ~ 20 — 50 was observed on 2004 June 23, a date before definite activity had previously been recorded from this shower. Consequently, in the latest upgrade of the List, the shower's start date has been altered to try to ensure future activity so early is caught, and we encourage all observers to routinely monitor throughout the expected activity period, in case of fresh outbursts. Prior to 1998, only three more probable returns had been detected, in 1916, 1921 and 1927, and with no significant reports between 1928 and 1997, it seemed likely these meteoroids no longer encountered Earth. The dynamics of the stream were poorly understood, although recent theoretical modelling has improved our comprehension. The shower's parent Comet 7P/Pons-Winnecke has an orbit that now lies around 0.24 astronomical units outside the Earth's at its closest approach. It was last at perihelion in 2002, and is next due on September 26 this year. Clearly, the 1998 and 2004 returns resulted from material shed by the comet in the past, which now lies on slightly different orbits to the comet itself. Dust trails laid down at various perihelion returns during the 19th century seem to have been responsible for the last two main outbursts. There were no predictions in force for possible activity in 2008 at the time of writing, but conditions for checking are quite favourable from the mid-northern latitudes where the radiant is best-seen. Last quarter Moon, though rising by midnight on June 26/27 from such locations, should be only a small problem after it appears, though the prolonged — in some places continuous — twilight means the summer nights are short anyway. The radiant is usefully accessible virtually all night, and all observing techniques can be employed.
July to SeptemberWith the former minor showers of the Pegasids and July Phoenicids having proven undetectable in the latest full IMO analyses, and so deleted from the Working List, this leaves just the Antihelion Source active and more or less visually identifiable for most of July, while its radiant area moves steadily through eastern Sagittarius and across northern Capricornus into south-west Aquarius. Results suggest the Source may not be especially recognisable after the first few days however, as ZHRs for most of the month seem < 2. Activity appears to improve somewhat, with ZHRs ~ 2 to 3, by late July and through the first half of August. This level of ZHRs may make it more practical to still identify the moonless α-Capricornid maximum, despite that radiant's overlap with the Antihelion Source's.
The Southern δ-Aquariids are strong enough, and the Piscis Austrinids have a radiant probably distant enough from the ANT area, that both should still be separable from it, particularly from the southern hemisphere. By the best from the major, and partly moonlit, Perseids, ANT ZHRs will likely have dropped back below 2 again, as the radiant tracks on through Aquarius, and into western Pisces by the α-Aurigid maximum on the August-September boundary. Only the κ-Cygnid peak is completely lost this August, as their peak is just the day after full Moon, on August 17.
Both the newly-renamed September Perseids (formerly the δ-Aurigids) and what we now term the δ-Aurigids proper, separated into two showers, even though they follow one another directly on exactly the same radiant drift track, have maxima that should be recordable in September, skies permitting. For most of September, ANT rates can still be detected from the radiant in Pisces, albeit probably no better than 2 — 3, but remember that from September 25, Antihelion meteors are no longer to be recorded as such, as both Taurid showers take over the near-ecliptic shower baton until late November.
For daylight radio observers, the interest of May-June has waned, but there remain the visually-impossible γ-Leonids (peak towards August 25, 04h UT, albeit not found in recent radio results), and a tricky visual shower, the Sextantids. Their maximum is expected on September 27, around 04h UT, but may possibly occur a day earlier. In 1999 a strong return was detected at λsol ~ 186°, equivalent to 2008 September 28, while in 2002, the September 27 peak was not found, but one around September 29 — 30 was! It seems plausible that several minor maxima in early October may also be due to this radio shower. New Moon creates no additional difficulties for visual observers hoping to catch some Sextantids in late September, though radiant-rise is less than an hour before dawn in either hemisphere.
[img]http://www.imo.net/galleries/calendar/summer08.png[/img]Piscis Austrinids (PAU)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]July 15 — August 10[/td][/tr][tr][td]Maximum: [/td][td]July 27 (λsol = 125°)[/td][/tr][tr][td]ZHR = [/td][td]5[/td][/tr][tr][td]Radiant: [/td][td]α = 341° δ = -30°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]35 km/s; [i]r[/i] = 3.2[/td][/tr][tr][td]TFC: [/td][td]α = 255° to 000° δ = 00° to +15°[/td][/tr][tr][td][/td][td]choose pairs separated by about 30° in α (β < 30° N)[/td][/tr][/table]
Very little information has been collected on the Piscis Austrinids in recent decades, so the details on the shower are not well-confirmed, and it seems possible the ZHR may be a little optimistic. However, that impression may simply be due to the large amount of northern hemisphere summer data, and the almost complete lack of southern hemisphere winter results, on it. The stream seems to be rich in faint meteors, rather like the nearby ANT and SDA, so telescopic work is advisable to try to establish more about it. Along with all the late July shower peaks this year, the PAU benefits from a nearly-new Moon.
Southern δ-Aquariids (SDA)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]July 12 — August 19[/td][/tr][tr][td]Maximum: [/td][td]July 27 (λsol = 125°)[/td][/tr][tr][td]ZHR = [/td][td]20[/td][/tr][tr][td]Radiant: [/td][td]α = 339° δ = -16°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]41 km/s; [i]r[/i] = 3.2[/td][/tr][tr][td]TFC: [/td][td]α = 255° to 000° δ = 00° to +15°[/td][/tr][tr][td][/td][td]choose pairs separated by about 30° in α (β < 40° N)[/td][/tr][/table]
One of the biggest changes brought about in the revamp of the Working List was the removal of the former streams of the Northern δ-Aquariids, and the Northern and Southern ι-Aquariids, all of which proved separately unidentifiable in a series of recent IMO and non-IMO analyses. This greatly simplifies matters for visual observers especially, who often struggled because of the confusion of minor radiants thought present in the Aquarius-Capricornus region during July-August. Like the PAU and ANT, the SDA meteors are often faint, thus are suitable targets for telescopic observing, although enough brighter members exist to make visual and imaging observations worth the effort too, primarily from more southerly sites. Radio work can pick up the SDA as well, and indeed the shower has sometimes given a surprisingly strong radio signature. Careful visual plotting is advised, to help with accurate shower association. The SDA/PAU/ANT/CAP radiants are well above the horizon for much of the night. The moonless maximum may not be quite so sharp as the single date suggested here might imply, perhaps lasting with similar activity from July 27 — 29. Its rates have been suspected of some variability at times too, though not in the more recent investigations.
α-Capricornids (CAP)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]July 3 — August 15[/td][/tr][tr][td]Maximum: [/td][td]July 29 (λsol = 127°)[/td][/tr][tr][td]ZHR = [/td][td]4[/td][/tr][tr][td]Radiant: [/td][td]α = 307° δ = -10°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]23 km/s; [i]r[/i] = 2.5[/td][/tr][tr][td]TFC: [/td][td]α = 255° to 000° δ = 00° to +15°[/td][/tr][tr][td][/td][td]choose pairs separated by about 30° in α (β < 40° N)[/td][/tr][tr][td]IFC: [/td][td]α = 300° δ = +10° (β > 45° N)[/td][/tr][tr][td][/td][td]α = 320° δ = -05° (β 0° to 45° N)[/td][/tr][tr][td][/td][td]α = 300° δ = -25° (β < 0°)[/td][/tr][/table]
The α-Capricornids and SDA were both definitely detected visually in former years, standing out against the much weaker other radiants supposed active in Capricornus-Aquarius then. Whether the CAP can still be detected separately from the new ANT radiant area remains to be discovered, as its radiant now partly overlaps that of the large ANT oval region. In their favour, CAP meteors are noted for being bright, at times even of fireball-class, which, combined with their low apparent velocity, can make some of these objects among the most impressive and attractive an observer could wish for. A minor enhancement of CAP ZHRs to ~ 10 was noted in 1995 by European IMO observers. More recent results suggest the maximum may continue for an extra day, so perhaps from July 29 — 30 this year.
Perseids (PER)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]July 17 — August 24;[/td][/tr][tr][td]Maximum: [/td][td]August 12 11h30m — 14h00m UT (λsol = 140°0 — 140°1) but see text[/td][/tr][tr][td]ZHR = [/td][td]100[/td][/tr][tr][td]Radiant: [/td][td]α = 49° δ = +58°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]59 km/s; [i]r[/i] = 2.6[/td][/tr][tr][td]TFC: [/td][td]α = 019° δ = +38° and α = 348° δ = +74° before 2h local time[/td][/tr][tr][td][/td][td]α = 043° δ = +38° and α = 073° δ = +66° after 2h local time (β > 20° N)[/td][/tr][tr][td]IFC: [/td][td]α = 300° δ = +40° and α = 000° δ = +20° or[/td][/tr][tr][td][/td][td]α = 240° δ = +70° (β > 20° N)[/td][/tr][/table]
The Perseids were one of the most exciting and dynamic meteor showers during the 1990s, with outbursts at a new primary maximum producing EZHRs of 400+ in 1991 and 1992. Rates from this peak decreased to ~ 100 — 120 by the late 1990s, and in 2000, it first failed to appear. This was not unexpected, as the outbursts and the primary maximum (which was not noticed before 1988), were associated with the perihelion passage of the Perseids' parent comet 109P/Swift-Tuttle in 1992. The comet's orbital period is about 130 years, so it is now receding back into the outer Solar System, and theory predicts that such outburst rates should dwindle as the comet to Earth distance increases. However, additional predictions suggested 2004 — 2006 might bring a return of enhanced rates ahead of the usual maximum, and in 2004 a short, strong peak happened close to that anticipated pre-peak time, though activity seemed to be roughly normal in 2005, and the 2006 return was badly moonlit and poorly-observed.
An average annual shift of +0°05 in the solar longitude of the `old' primary peak had been deduced from 1991 — 99 data, and allowing for this could give a possible recurrence time around 16h40m UT on August 12 (λsol = 140°21), if so a few hours after the most probable maximum, that of the 'traditional' peak always previously found, given above. The timing of a tertiary peak, not seen in IMO data since 1999, would be around λsol = 140°4, 21h30m UT on August 12. While recent observations imply only the 'traditional' peak is liable to recur in 2008, observers should be aware of these additional timings as possibilities, and plan their efforts accordingly, just in case!
[img]http://www.imo.net/galleries/calendar/per08.png[/img]The waxing gibbous Moon will be setting between local midnight and 01h30m on August 12/13 for the mid-northern latitudes best-placed to follow the shower (moonset is progressively earlier for places further north), leaving some dark skies to cover whatever happens. For these same locations, the Perseid radiant is viably observable from 22h — 23h local time onwards, gaining altitude throughout the night, so circumstances overall are quite favourable. The 'traditional' maximum timing would be best-viewed from places in and around the northern Pacific Ocean, including the extreme west of North America west as far as extreme eastern Japan and China, assuming it happens as expected.
All forms of observing can be usefully carried out on the shower. For example, video data has been used in the latest IMO analyses to clarify and refine the radiant position for the shower — and to confirm that the occasional visual suspicions the radiant may be multiple are almost certainly only illusory. The only negative aspect to the shower is the impossibility of covering it from the bulk of the southern hemisphere.
Aurigid-Perseid Showersα-Aurigids (AUR)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]August 25 — September 8[/td][/tr][tr][td]Maximum: [/td][td]August 31 19h UT (λsol = 158°6)[/td][/tr][tr][td]ZHR = [/td][td]7[/td][/tr][tr][td]Radiant: [/td][td]α = 84° δ = +42°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]66 km/s; [i]r[/i] = 2.6[/td][/tr][tr][td]TFC: [/td][td]α = 052° δ = +60°; α = 043° δ = +39°[/td][/tr][tr][td][/td][td]and α = 023° δ = +41° (β > 10° S)[/td][/tr][/table]
September Perseids (SPE)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]September 5 — 17[/td][/tr][tr][td]Maximum: [/td][td]September 9 03h UT (λsol = 166°7)[/td][/tr][tr][td]ZHR = [/td][td]5[/td][/tr][tr][td]Radiant: [/td][td]α = 60° δ = +47°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]64 km/s; [i]r[/i] = 2.9[/td][/tr][tr][td]TFC: [/td][td]As AUR[/td][/tr][/table]
δ-Aurigids (DAU)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]September 18 — October 10[/td][/tr][tr][td]Maximum: [/td][td]September 28 (λsol = 186°) but see text[/td][/tr][tr][td]ZHR = [/td][td]3[/td][/tr][tr][td]Radiant: [/td][td]α = 82° δ = +49°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]64 km/s; [i]r[/i] = 2.9[/td][/tr][tr][td]TFC: [/td][td]As AUR[/td][/tr][/table]
[img]http://www.imo.net/galleries/calendar/aurdau07.png[/img]These essentially northern hemisphere showers appear to be part of a series of poorly-observed sources with radiants in Aries, Perseus, Cassiopeia and Auriga, active from late August into October. British and Italian observers independently reported a possible new radiant in Aries during late August 1997 for example. IMO investigations using using data collected since 1986 have suggested there are at least three distinct showers which repeat annually, of which the α-Aurigids is the marginally stronger. The other two are the September Perseids and δ-Aurigids.
The α-Aurigids have produced short, unexpected, outbursts at times, with EZHRs of ~ 30 — 40 recorded in 1935, 1986 and 1994, although they have not been monitored regularly until very recently, so other events may have been missed. Only three watchers in total covered the 1986 and 1994 outbursts, for instance! The badly moonlit 2007 event, for which another, perhaps still stronger, outburst had been predicted, was still to come when this text was prepared, which, whether anything unusual occurred or not, may have implications for future returns. All three Aurigid-Perseid radiants reach useful elevations after 23h — 00h local time, and this year conditions are perfect for the α-Aurigid peak, with new Moon preceding it by just one day.
The September Perseids were formerly called the 'δ-Aurigids' on the IMO Working List of Visual Showers, with that earlier shower now separated into two. The final decision on the relevance of the separation has to be based on multiple-station imaging. The date of the split between the two has been set to coincide with the lowest ZHRs from either, and the showers should be treated as distinct in your observations at present. The September 9 maximum is favoured by a waxing gibbous Moon, which sets at about the time the radiant can first be properly observed, between 23h — 00h, from mid-northern locations.
As the less active phase of the new September Perseids, the δ-Aurigids seem to give a weak and very ill-defined maximum between roughly λsol = 181° — 191° (2008 September 23 to October 3). September 28 is about the middle of this peak interval, which almost coincides with new Moon this year, though the earlier part of this maximum spell will still have some problems from the last quarter Moon, because the radiant and the Moon will be nicely risen only after local midnight.
Telescopic data to examine all the radiants in this region of sky — and possibly observe the telescopic β-Cassiopeids simultaneously — would be especially valuable, but still-imaging, video records and visual plotting would be welcomed too.
October to DecemberA weak final quarter to the year sees the best from the most active showers lost to the bright Moon, though there are still some positive aspects to it. While the latter stages of the minor δ-Aurigid peak may carry over into the opening days of October, the Antihelion Source's activity does not. Indeed, the ANT is to be considered in abeyance in favour of the Taurids from late September until late November, when the Antihelion radiant centre returns to activity in eastern Taurus. During December, it tracks across southern Gemini, and although analyses indicate its likely ZHRs are < 2 for most of this time, some of this apparent inactivity may be due to the strength of the Geminids very close-by to the north during part of December, plus also the minor Monocerotids a little way to its south simultaneously.
In 2005 and 2006, European video observers recorded short-lived outbursts from a north-circumpolar radiant near the 'tail' of Draco, around the Dra-Cam border, on October 5/6. The 2005 event (only) was recorded very weakly by radio, but no visual results confirmed either occurrence. Any 2007 event was still to come when this was written, but 2008 brings a good chance to check for it again. The 2005 — 06 events happened between λsol ~ 192°55 — 192°64, equivalent to 2008 October 5, 13h15m — 15h30m UT. The radiant was found around α ~ 165°, δ ~ +78°, the meteors with an atmospheric velocity of ~ 45 — 50 km/s. If the active interval keeps to the same time, it would be best-observed from central Asia east to the extreme west of North America, and has only a waxing crescent Moon as accompaniment.
The potential Draconid epoch in early October survives the Moon, but the minor ε-Geminids (peak due on October 18) and the major Orionids (maximum expected on October 20/21) have a waning gibbous to last quarter Moon, visible when their radiants are, so will likely struggle to be usefully seen. However, following the unexpectedly strong Orionid activity in 2006, when ZHRs were around 50 — 60 at best, with many bright meteors, and the fact the shower may be nearing the peak of its theoretical 12-year cycle (like its twin, the η-Aquariids of April-May), observing may still be worthwhile, in case such better rates should manifest again this year. The new very weak possible shower of the Leo Minorids has fewer moonlight problems in late October, while October's new Moon also assists viewing the possible Taurid 'swarm' return interval in late October to early November.
The Leonids may produce just a normal maximum close to their 'traditional' nodal time in 2008, on November 17, around 09h UT, though the bright waning Moon will be a severe problem if so. However, Mikhail Maslov proposed that the shower may show a peak with ZHRs ~ 130 at 00h22m UT on November 17 in [i]WGN[/i] 35:1 (2006, p. 7), with meteors brighter than average. Many of his other model calculations for the Leonids in the period 2001 — 2006 showed some differences to what was actually observed, so while this this is an interesting possibility for 2008, its accuracy is unknown and unproven. Jérémie Vaubaillon finds instead two potential stream encounters, centred on November 17 at 01h32m UT (1466 trail; ZHR most uncertain — perhaps ~ 50, but maybe ~ 25 — 100) and November 18 at 21h38m UT (1932 trail; ZHR possibly ~ 20 at best?). Checking on all these times (or any others that may be suggested subsequently) will be difficult due to the Moon, but valuable.
[img]http://www.imo.net/galleries/calendar/winter08.png[/img]Later in November, the α-Monocerotids should peak far enough after last quarter Moon to mostly survive the moonlight. Into December, and the Phoenicids have a bright Moon to contend with for their possible maximum, due at about 03h UT on December 6, with a similar problem for what may be the better activity during early December for the Puppids-Velids. The minor Monocerotids just survive the waxing Moon, but the σ-Hydrid (December 11) and Geminid (December 13, 23h ± 2hr) maxima are both too near full Moon for detailed visual observations. The Geminids' strength does mean they would be worth looking out for if skies are clear though, but more out of casual interest than scientific investigation. The year does at least end better, with largely moonless returns of the Ursids and Coma Berenicids.
Draconids (GIA)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]October 6 — 10[/td][/tr][tr][td]Maximum: [/td][td]October 8 10h30m UT (λsol = 195°4 but see below)[/td][/tr][tr][td]ZHR = [/td][td]periodic up to storm levels[/td][/tr][tr][td]Radiant: [/td][td]α = 262° δ = +54°[/td][/tr][tr][td]Radiant drift: [/td][td]negligible[/td][/tr][tr][td]vinf = [/td][td]20 km/s; [i]r[/i] = 2.6[/td][/tr][tr][td]TFC: [/td][td]α = 290° δ = +65° and α = 288° δ = +39° (β > 30° N)[/td][/tr][/table]
The Draconids are primarily a periodic shower which produced spectacular, brief, meteor storms twice last century, in 1933 and 1946, and lower rates in several other years (ZHRs ~ 20 — 500+). Most detected showers were in years when the stream's parent comet, 21P/Giacobini-Zinner, returned to perihelion, as it did last in 2005 July. Its orbital period is currently about 6.6 years. In 2005 October, a largely unexpected outburst happened near the comet's nodal crossing time, around λsol = 195°40 — 195°44, probably due to material shed in 1946. Visual ZHRs were ~ 35, though radar detections suggested a much higher estimated rate, closer to ~ 150. The peak was found in radio results too, but it did not record especially strongly that way. Outlying maximum times from the recent past have spanned from λsol = 195°075 (in 1998; EZHRs ~ 700), equivalent to 2008 October 8, 02h40m UT, through the nodal passage time above, to λsol = 195°63 — 195°76 (a minor outburst in 1999, not a perihelion-return year; ZHRs ~ 10 — 20), equating to 2008 October 8, 16h — 19h30m UT. The radiant is circumpolar from many northern hemisphere locations, but is higher in the pre-midnight and near-dawn hours of early October. For such sites, the waxing gibbous Moon rises between ~ 21h — 23h local solar time on October 7/8 and between ~ 23h — 00h on October 8/9, meaning the first part of the night is available for dark-sky checking, whatever the shower may yield — even if that is nothing detectable. Draconid meteors are exceptionally slow-moving, a characteristic which helps separate genuine shower meteors from sporadics accidentally lining up with the radiant.
Leo Minorids (LMI)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]October 19 — 27[/td][/tr][tr][td]Maximum: [/td][td]October 24 (λsol = 211°)[/td][/tr][tr][td]ZHR = [/td][td]2[/td][/tr][tr][td]Radiant: [/td][td]α = 162° δ = +37°[/td][/tr][tr][td]Radiant drift: [/td][td]See Table 6[/td][/tr][tr][td]vinf = [/td][td]62 km/s; [i]r[/i] = 3.0[/td][/tr][tr][td]TFC: [/td][td]α = 190° δ = +58° and α = 135° δ = +30° (β > 40° N)[/td][/tr][/table]
The second new addition to the Working List during the current revision, this is a weak minor shower, and its peak ZHR appears to be on or below the visual threshold. Low rates may be a result of neglecting the shower during the vast majority of late-October observations though. Imaging results have found signs of a radiant near the proposed position, but there is almost no reliable visual information on when the shower is most probably active, nor when its peak is. The details above are simply a best-guess. The radiant area can be seen only from the northern hemisphere, and rises around midnight. The proposed maximum date sees the waning crescent Moon rising between 01h — 02h at mid-northern latitudes, but this should not be too great a problem even so. Telescopic or imaging observations are advised.
[img]http://www.imo.net/galleries/calendar/lmi08.png[/img]TauridsSouthern Taurids (STA)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]September 25 — November 25[/td][/tr][tr][td]Maximum: [/td][td]November 5 (λsol = 223°)[/td][/tr][tr][td]ZHR = [/td][td]5[/td][/tr][tr][td]Radiant: [/td][td]α = 52° δ = +15°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]27 km/s; [i]r[/i] = 2.3[/td][/tr][tr][td]TFC: [/td][td]Choose fields on the ecliptic and ~ 10° E or W of the radiants (β > 40° S)[/td][/tr][/table]
Northern Taurids (NTA)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]September 25 — November 25[/td][/tr][tr][td]Maximum: [/td][td]November 12 (λsol = 230°)[/td][/tr][tr][td]ZHR = [/td][td]5[/td][/tr][tr][td]Radiant: [/td][td]α = 58° δ = +22°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]29 km/s; [i]r[/i] = 2.3[/td][/tr][tr][td]TFC: [/td][td]as Southern Taurids[/td][/tr][/table]
These two streams form part of the complex associated with Comet 2P/Encke. Defining their radiants is best achieved by careful visual or telescopic plotting, or imaging recordings, since they are large and diffuse. Each radiant should be considered an oval area of ~ 20° by 10°, α by δ, centred on the radiant position for that date, for shower association. Their activity very clearly dominates the Antihelion Source area's during the northern autumn, so much so that the ANT is considered inactive while they are present.
The brightness and relative slowness of many shower meteors makes them ideal targets for still-imaging, while these factors coupled with low, steady, combined Taurid rates makes them excellent subjects for newcomers to practice their plotting techniques on. The activity of both showers produces an apparently plateau-like maximum for about ten days in early November, and they have a reputation for producing some excellently bright fireballs at times, although seemingly not in every year.
Studies by David Asher have indicated that increased Taurid fireball rates may result from a 'swarm' of larger particles within the Taurid stream complex, and he suggested such 'swarm' returns might happen in 1995, 1998 and 2005 most recently. In 1995, an impressive crop of bright Taurids occurred between late October to mid November, while in 1998, Taurid ZHRs reached levels comparable to the usual maximum rates in late October, together with an increased flux of brighter Taurids generally. The 2005 event was the most impressive and best-observed yet, with a lot of, occasionally very brilliant, fireballs, and enhanced combined ZHRs of ~ 10 — 15, that persisted from about October 29 to November 10. Another 'swarm' return is predicted for 2008, while late October into early November has a new to first quarter Moon, so all observers should be alert to cover whatever happens (but do remember that nothing is ever guaranteed in meteor astronomy!).
The Southern Taurid maximum will have relatively little lunar interference, but the Northern peak falls just a day before full Moon, so will likely be missed this time. The near-ecliptic radiants for both shower branches mean all meteoricists can observe these streams, albeit northern hemisphere observers are somewhat better-placed, as here suitable radiant zenith distances persist for much of the night. Even in the southern hemisphere, a good 3 — 5 hours' watching around local midnight is possible with Taurus well above the horizon, however.
α-Monocerotids (AMO)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]November 15 — 25[/td][/tr][tr][td]Maximum: [/td][td]November 21 09h25m UT (λsol = 239°32)[/td][/tr][tr][td]ZHR = [/td][td]variable - usually ~ 5 but may produce outbursts to ~ 400+[/td][/tr][tr][td]Radiant: [/td][td]α = 118° δ = +01°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]65 km/s; [i]r[/i] = 2.4[/td][/tr][tr][td]TFC: [/td][td]α = 115° δ = +23° and α = 129° δ = +20° (β > 20°&;nbsp;N)[/td][/tr][tr][td][/td][td]or α = 110° δ = -27° and α = 098° δ = +06° (β < 20° N)[/td][/tr][/table]
A 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. However, the proposed ten-year periodicity in such returns passed unconfirmed when nothing unusual took place during the moonlit shower of 2005. Due to this, all observers need to monitor this source closely in every year, to try to spot the next outburst. The brevity of all past outbursts means breaks under clear skies should be kept to an absolute minimum near the predicted peak. Although the Moon is a waning crescent on November 21, it will rise between 00h and 01h across the globe then, which will make it something of a nuisance, as the AMO radiant is well on view from either hemisphere only after about 23h local time. If correct, the peak timing would fall well for sites across North and Central America.
Monocerotids (MON)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]November 27 — December 17[/td][/tr][tr][td]Maximum: [/td][td]December 8 (λsol = 257°)[/td][/tr][tr][td]ZHR = [/td][td]2[/td][/tr][tr][td]Radiant: [/td][td]α = 100° δ = +08°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6;[/td][/tr][tr][td]vinf = [/td][td]42 km/s; [i]r[/i] = 3.0[/td][/tr][tr][td]TFC: [/td][td]α = 088° δ = +20° and α = 135° δ = +48° (β > 40° N)[/td][/tr][tr][td][/td][td]or α = 120° δ = -03° and α = 084° δ = +10° (β < 40° N)[/td][/tr][/table]
Only low rates are likely from this very minor source, making accurate visual plotting, telescopic or video work essential, particularly because the meteors are normally faint. The shower's details, even including its radiant position, are rather uncertain. Recent IMO data showed only weak signs of a maximum as indicated above. Telescopic results have suggested a later maximum, around λsol ~ 264°, 2008 December 15, from a radiant at α = 117°, δ = +20°. The waxing Moon sets between 01h and 02h30m on December 8, reasonable news as the radiant area is on-show virtually all night, culminating about 1h30m local time. A December 15 peak would be very unfavourable however, as too near full Moon.
Ursids (URS)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]December 17 — 26[/td][/tr][tr][td]Maximum: [/td][td]December 22 07h30m UT (λsol = 270°7)[/td][/tr][tr][td]ZHR = [/td][td]10 (occasionally variable up to 50)[/td][/tr][tr][td]Radiant: [/td][td]α = 217° δ = +76°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]33 km/s; [i]r[/i] = 3.0[/td][/tr][tr][td]TFC: [/td][td]α = 348° δ = +75° and α = 131° δ = +66° (β > 40° N)[/td][/tr][tr][td][/td][td]α = 063° δ = +84° and α = 156° δ = +64° (β 30° to 40° N)[/td][/tr][/table]
[img]http://www.imo.net/galleries/calendar/urs.png[/img]
A very poorly-observed northern hemisphere shower, but one which has produced at least two major outbursts in the past 70 years, in 1945 and 1986. Several other rate enhancements, recently in 1988, 1994, 2000 and 2006 (when ZHRs were around 30 for two hours or more), 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 λsol = 270°8, for instance, which might suggest a slightly later maximum time in 2008 of December 22, ~ 10h UT, while the 2000 enhancement was seen surprisingly strongly (EZHR ~ 90) by video at λsol = 270°78 (equivalent to 2008 December 22, 09h30m UT), although the visual enhancement then was much less, ZHR ~ 30. Whether the relative proximity of the shower's parent comet, 8P/Tuttle, at perihelion on January 26 this year, will have any influence on the shower this December, is unclear, though no such direct linkage has been apparent previously. 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. The waning crescent Moon should cause few difficulties for observing the maximum on this occasion, and if any recur as suggested, the peak timings should favour northerly sites between North America westwards across the Pacific Ocean to east Asia, including Japan and China.
Coma Berenicids (COM)[table][tr][td][/td][td][/td][/tr][tr][td]Active: [/td][td]December 12 — January 23[/td][/tr][tr][td]Maximum: [/td][td]December 29 (λsol = 278°)[/td][/tr][tr][td]ZHR = [/td][td]5[/td][/tr][tr][td]Radiant: [/td][td]α = 185° δ = +21°[/td][/tr][tr][td]Radiant drift: [/td][td]see Table 6[/td][/tr][tr][td]vinf = [/td][td]65 km/s; [i]r[/i] = 3.0[/td][/tr][tr][td]TFC: [/td][td]α = 180° δ = +50° and α = 165° δ = +20° before 3h local time[/td][/tr][tr][td][/td][td]α = 195° δ = +10° and α = 200° δ = +45° after 3h local time (β > 20° N)[/td][/tr][/table]
One of the significant bonuses of the new Working List upgrade has been to define a rather better visual activity profile for the Coma Berenicids than had been possible previously. The shower was confirmed as quite weak, but apparently long-lasting, though coverage after the Quadrantid epoch in January still left many gaps, a period which needs more observations. The maximum was found to be about ten days later in December than previously thought too, hence the amended parameters above.
The radiant ephemeris of the shower is severely questioned after the scrutinization of single-station video data showing a clear radiant drift with an offset of about 15° to the Working List positions. The result is given as 'possible COM' in the figure below. We recommend to use the old positions in 2008, while meteors from the 'possible COM' position should be noted separately.
[img]http://www.imo.net/galleries/calendar/com08.png[/img]In 2006, Spanish video observers reported an unexpected COM outburst on December 24/25, with EZHRs suggested as perhaps ~ 60, but this was not apparent in any of the radio observations then, nor in another detailed set of video observations made in Italy at the same time, so it remains uncertain. Since the possible outburst came from the 'old' COM position, the new ephemeris from video data may actually indicate a separate source rather than an erroneous COM drift.
There is much we still do not know about this shower, and as it is almost unobservable from the southern hemisphere, northern watchers must brave the winter cold to improve matters. The radiant is at a useful elevation from local midnight onwards, and new Moon near the probable peak makes this a particularly good year to make observations. holdy，你这两个表里，关于御夫座的描述，相差也太远了哦 已经修正过来~~~ 好，最喜欢流星雨了，要是能翻译成中文就好了 应该学好英文再发帖才是最好~根本看不懂嘛! 学习天文也要同时学习英语的，呵呵 顶
不知道有没有好天气看啊 期待哦~ 顶
不知道有没有天气看哦 期待
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