April to June

Meteor activity picks up towards the April-May boundary, with shower peaks from the moonless Lyrids and pi-Puppids. In early May, the eta-Aquarids are lost to full Moon for their main broad maximum around May 5. Later in May and throughout June, most of the meteor action switches to the daytime 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, 2h UT
delta-Piscids	April 24, 2h UT
epsilon-Arietids	May 9, 1h UT
May Arietids	May 16, 2h UT
o-Cetids	May 20, 1h UT
Arietids	June 7, 4h UT
zeta-Perseids	June 9, 1h UT
beta-Taurids	June 28, 3h UT

Signs of most of these peaks were found in radio data from 1994-2001, though some are difficult to define because of their proximity to other sources, while the Arietid and zeta-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 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, with their probable peaks in May-June. Checking for any possible June Lyrids will be very practical, and although the waxing Moon makes June Bootid hunting difficult, it is very important this year.

Lyrids

Active       : April 16-25;
Maximum      : April 22, 04h 10m UT (sol = 32.32°);
ZHR          = 18 (can be variable, up to 90);
Radiant      : alpha = 271°, delta = +34°;
Radiant drift: see Table 6;
V            = 49 km/s;
r            = 2.9;
TFC          : alpha = 262°, delta = +16° and
               alpha = 282°, delta = +19° (beta>10° S).

Figure 3: Radiant position and drift of the Lyrids

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 sol = 32.0°-32.45° (equivalent to 2004 April 21, 20h 20m UT to April 22, 7h 20m UT), with an ideal time of sol = 32.32°. Although the mean peak ZHR was 18 over the thirteen years, actual peak ZHRs varied dependent on when the maximum time 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 maximum 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 (FWHM) time. It varied from 14.8 h in 1993 to 61.7 h in 2000, with a mean value of 32.1 h. 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 the Lyrids worth watching, since we cannot say when the next unusual return may occur.

The shower is best viewed from the northern hemisphere, but it is visible from many sites north and south of the equator, and is suitable for all forms of observation. As the shower's radiant rises during the night, watches can be usefully carried out from about 22h 30m local time onwards. The waxing crescent Moon sets around or well before this time for mid-northern sites on April 21/22, and still sooner further south, so gives no problems. The ideal maximum time, if it recurs, would be best-seen from sites in and immediately adjacent to the North Atlantic Ocean (between roughly longitudes 10° to 70° W). Other maxmum times are perfectly feasible, as outlined earlier.

pi-Puppids

Active       : April 15-28;
Maximum      : April 23, 9h UT (sol = 33.5°);
ZHR          = periodic, up to around 40;
Radiant      : alpha = 110°, delta = -45°;
Radiant drift: see Table 6;
V            = 18 km/s;
r            = 2.0;
TFC          : alpha = 135°, delta = -55° and
               alpha = 105°, delta = -25° (beta<20° N).

Figure 4: Radiant position and drift of the pi-Puppids

This is a young stream produced by Comet 26P/Grigg-Skjellerup, and shower activity has only been detected from it since 1972. Notable short-lived shower 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 October 2002, but no readily detectable rates were found in April 2003. However, regular monitoring during the shower's activity in future is vital, as coverage has commonly been patchy, and short-lived showers could have been missed in the past.

The pi-Puppids are best seen from the southern hemisphere, with useful observations mainly practical before local midnight, as the radiant is very low to setting after 1h local time. The waxing crescent Moon will be setting by roughly 19h-20h local time from such locations on April 22/23, allowing plenty of dark skies for watching. Well-placed sites are likely to be across the Southern Pacific Ocean, including all of New Zealand and possibly the extreme eastern part of Australia, 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.

June Lyrids

Active       : June 11-21;
Maximum      : June 15 (sol = 85°);
ZHR          = variable, 0 - 5;
Radiant      : alpha = 278°, delta = +35°;
Radiant drift: June 10 alpha = 273°, delta = +35°,
               June 15 alpha = 277°, delta = +35°,
               June 20 alpha = 281°, delta = +35°;
V            = 31 km/s;
r            = 3.0;

Figure 5: Radiant position and drift of the June Lyrids

This shower 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 2004 benefits from a nearly-new Moon on June 15, and we urge all observers who can to cover this possible stream. The radiant is a few degrees south of the bright star Vega (alpha Lyrae), so will be 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 Bootids

Active       : June 26-July 2;
Maximum      : June 27, 01h 45m UT (sol = 95.7°);
ZHR          = variable, 0 - 100;
Radiant      : alpha = 224°, delta = +47°;
Radiant drift: see Table 6;
V            = 14 km/s;
r            = 2.2;
TFC          : alpha = 156°, delta = +64° and
               alpha = 289°, delta = +67° (beta=25..60° N).

Figure 6: Radiant position and drift of the June Bootids

Following the wholly unexpected strong return of this shower in 1998, when ZHRs of 50-100+ were visible for more than half a day, we reintroduced this source to the Working List of Visual Meteor Showers, and encourage all observers to routinely monitor the expected activity period 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 are poorly understood, although recent theoretical modelling has attempted to resolve this problem. The shower's parent Comet 7P/Pons-Winnecke was at perihelion in January 1996 and again in May 2002. Its orbit currently lies around 0.24 astronomical units outside the Earth's at its closest approach, so the 1998 return probably resulted from material shed by the comet in the past (the comet's perihelion returns of 1819 and 1869, or 1825, have been suggested as probable origin dates). A substantial part of these meteoroids are thought to have become trapped in a mean-motion resonance with Jupiter, and presently are in an Earth-intersecting orbit. Work by Juergen Rendtel indicates the Earth may encounter potentially substantial June Bootid rates again in 2004 on June 27, around 1h UT. Thus although the waxing gibbous Moon will be a nuisance on June 26-27, it will set between local midnight and 1h for mid-northern sites, and as the radiant is at a useful elevation for most of the short summer night in the northern hemisphere (only), every effort should be made to secure as much data as possible. Remember too that other nights during the shower may also produce unexpected activity, even if the anticipated peak does not appear, so please be alert!