Meteor activity picks up towards the April-May boundary, with shower peaks from the Lyrids and π-Puppids in late April, then the η-Aquarids in early May, all readily available for observations without the Moon. 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 a few meteors from the o-Cetids and Arietids have been reported 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, 15h; δ-Piscids — April 24, 15h; ε-Arietids — May 9, 13h; May Arietids — May 16, 14h; o-Cetids — May 20, 13h; Arietids — June 7, 16h; ζ-Perseids — June 9, 16h; β-Taurids — June 28, 15h. Signs of most of these were found in radio data from 1994 —2004, though some are difficult to define individually because of their proximity to other radiants, while the Arietid and ζ-Perseid maxima tend to blend into one another, producing a strong radio signature for several days in early June. There are indications these two shower maxima now each occur up to a day later than indicated here too. The visual ecliptical complexes continue with some late Virginids up to mid April, after which come the minor Sagittarids, and their probable peaks in May —June. For northern observers, checking for any June Lyrids should be possible with only some lunar hindrance, while new Moon makes June Boötid hunting very favourable near their potential peak.
Lyrids (LYR)
Active: April 16 —25; Maximum: April 22, 16h30m UT (λ = 32°32, but may vary — see text);
ZHR = 18 (can be variable, up to 90);
Radiant: α = 271°, δ = +34°; Radiant drift: see Table 6 (page 23);
v∞ = 49 km/s; r = 2.9;
TFC: α = 262°, δ = +16° and α = 282°, δ = +19° (β > 10° S).
Audrius Dubietis and Rainer Arlt published a detailed investigation of the Lyrids in IMO results from 1988 —2000 in 2001, the most detailed examination of the shower in modern times. Several fresh features were found, the most important of which was to redefine the maximum time as variable from year to year between λ = 32°0 —32°45 (equivalent to 2006 April 22, 8h40m —19h00m UT), with an ideal time of λ = 32°32. Although the mean peak ZHR was 18 over the thirteen years, the actual highest ZHRs varied dependent on when the maximum occurred. A peak at the ideal time produced the highest ZHRs, ~ 23, while the further the peak happened from this ideal, the more the ZHRs were reduced, to as low as ~ 14. (The last very high rates occurred outside the examined interval, in 1982 over the USA, when a short-lived ZHR of 90 was recorded.) While generally thought of as having a short, quite sharp, maximum, this latest work revealed the shower’s peak length was variable too. This was measured by how long ZHRs were above half the maximum value, the Full-Width-Half-Maximum time. It varied from 14.8 hours in 1993 to 61.7 hours in 2000, with a mean value of 32.1 hours. Best rates are normally achieved for just a few hours however. One other aspect found, confirming data from earlier in the 20th century, was that occasionally, as their highest rates occurred, the Lyrids produced a short-lived increase of fainter meteors. Overall, the unpredictability of the shower in any given year always makes it worth watching, since we cannot say when the next unusual return may happen.
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Lyrids are best viewed from the northern hemisphere, but they are visible from many sites north and south of the equator, and are suitable for all forms of observation. As the shower’s radiant rises during the night, watches can be usefully carried out from about 22h30m local time onwards. The waning crescent Moon rises in morning twilight between ~ 2h30m —3h30m local time for mid-northern sites on April 22, giving plenty of darker skies for observers before this. For the mid-southern hemisphere, the Moon rises earlier, between midnight to 1 a.m., but still permits some useful watching. The ideal maximum time, if it recurs, would be best-seen from sites in central Asia eastwards to the Far East and Australia, but other timings are perfectly possible, as noted above.
π-Puppids (PPU)
Active: April 15 —28; Maximum: April 23, 21h30m UT (λ = 33°5);
ZHR = periodic, up to around 40;
Radiant: α = 110°, δ = -45°; Radiant drift: see Table 6 (page 23);
v∞ = 18 km/s; r = 2.0;
TFC: α = 135°, δ = -55° and α = 105°, δ = -25° (β < 20° N).
This is a young stream produced by Comet 26P/Grigg-Skjellerup, and activity has only been detected from it since 1972. Notable short-lived maxima of around 40 meteors per hour took place in 1977 and 1982, both years when the parent comet was at perihelion, but before 1982, little activity had been seen at other times. In 1983, a ZHR of about 13 was reported, perhaps suggesting that material has begun to spread further along the comet’s orbit, as theory predicts. Comet Grigg-Skjellerup reached perihelion last in late 2002, but nothing significant was detected from this source in 2003 April. The comet’s next perihelion passage is in 2008, so activity this year may be unlikely. However, regular monitoring during the shower in future is vital, as coverage has commonly been patchy, and short-lived maxima could have been missed in the past.
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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 1h local time. On April 23, the waning crescent Moon rises only well after this from such locations, creating a perfect observing opportunity. Well-placed sites are likely to be in southern Africa, if the maximum time proves correct. So far, visual and radio data have been collected on the shower, but the slow, bright nature of the meteors makes them ideal photographic subjects too. No telescopic or video data have been reported in any detail as yet.
η-Aquarids (ETA)
Active: April 19 —May 28; Maximum: May 6, 6h UT (λ = 45°5);
ZHR = 60 (periodically variable, ~ 40 —85);
Radiant: α = 338°, δ = -01°; Radiant drift: see Table 6 (page 23);
v∞ = 66 km/s; r = 2.4;
TFC: α = 319°, δ = +10° and α = 321°, δ = -23° (β < 20° S).
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-Aquarids 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 visual ZHRs should be around 50 —60 in 2006, according to this idea. Whatever the case, the waxing gibbous Moon on May 5 —6 will have long set for southern hemisphere viewers before the radiant is properly visible. 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.
June Lyrids (JLY)
Active: June 11 —21; Maximum: June 16 (λ = 85°); ZHR = variable, 0 —5;
Radiant: α = 278°, δ = +35°;
Radiant drift: June 10 α = 273°, δ = +35°,
June 15 α = 277°, δ = +35°,
June 20 α = 281°, δ = +35°;
v∞ = 31 km/s; r = 3.0.
This possible source does not feature in the current IMO Working List of Visual Meteor Showers, as apart from some activity seen from northern hemisphere sites in a few years during the 1960s (first seen 1966) and 1970s, evidence for its existence has been virtually zero since. In 1996, several observers independently reported some June Lyrids, though no definite activity has been found subsequently. The probable maximum in 2006 has a waning gibbous Moon, which rises in the half hour or so before local midnight, and we urge all observers who can to check for this possible stream in darker skies before moonrise. The radiant is a few degrees south of the bright star Vega (α Lyrae), so is well on-view throughout the short northern summer nights, but there are discrepancies in its position in the literature. All potential June Lyrids should be carefully plotted, paying especial attention to the meteors’ apparent velocities. Confirmation or denial of activity from this source by photography or video would be very useful too.
June Boötids (JBO)
Active: June 26 —July 2; Maximum: June 27, 14h00m UT (λ = 95°7);
ZHR = variable, 0 —100+;
Radiant: α = 224°, δ = +47°; Radiant drift: see Table 6 (page 23);
v∞ = 14 km/s; r = 2.2;
TFC: α = 156°, δ = +64° and α = 289°, δ = +67° (β = 25° —60° N).
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Following its unexpected return of 1998, when ZHRs of 50 —100+ were visible for more than half a day, this source was reinstated on the Working List of Visual Meteor Showers. A further 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. We encourage all observers to routinely monitor the expected activity period at least in case of future outbursts. Prior to 1998, only three definite returns had been detected, in 1916, 1921 and 1927, and with no significant reports between 1928 —1997, it seemed probable 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. Consequently, the 1998 and 2004 returns resulted from material shed by the comet in the past, and 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 are no predictions in force for possible activity in 2006 as yet, but new Moon on June 25 means if anything does occur during the shower’s possible active period, conditions will be ideal for all forms of observation. At mid-northern sites, the radiant is at a useful elevation for most of the short summer nights, so please be alert!