British Astronomical Association
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British Astronomical Association
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Meteor Section |
Following early January’s Quadrantids, the opening months of the year are generally regarded as a rather thin time for meteor observing, with only minor shower and low background sporadic activity in evidence. Even the most dedicated observers find the minimal rates - sometimes only one or two meteors per hour - in February and early March rather a trial on their patience.
Active March and April
Radiant RA 14h 04m Dec -09o
13h 36m -11o
Activity begins to pick up a little from late March with the arrival of the Virginids. The shower is part of an essentially year-long ‘drizzle’ of meteor activity from close to the ecliptic plane. In common with other near-ecliptic showers, the Virginids show a split radiant, presumably a consequence of gravitational perturbations by the planets. Activity comes from radiants in the Virgo ‘Bowl’, and to the east of Spica, fairly low in the southern spring sky for UK-based observers. A result of the low radiant elevation is that Virginid meteors can, on occasion, have long, slow trajectories up from the horizon towards the zenith.
Observed Virginid rates are typically low, usually no better than 2-3 meteors/hr in late March and early April. The meteors can, however, sometimes be reasonably bright by way of reward for the patient observer. Watches in the post-midnight hours are likely to be most productive, and the dark of the Moon interval from the end of March until mid-April will be the most favourable time to observe this low-activity, poorly-covered shower.
Active April 19-25
Radiant RA 18h 98m Dec +32o
Usually, the shower which ‘re-opens’ the more active part of the meteor observer’s year, the Lyrids are unfortunately-timed in 2005, Full Moon coinciding with their April 21-22 maximum.
Active April 24-May 20
Radiant RA 22h 20m Dec -01o
An excellent shower for observers at southerly latitudes, the Eta Aquarids present a considerable challenge for those in the British Isles. The shower radiant, near the ‘Water Jar’ asterism in Aquarius, is only just beginning to climb in the eastern sky as dawn breaks in early May.
Radiant elevation at 53oN
Local Time Alt
02 3.9o
03 12.8o
04 21.0o
The Eta Aquarids are, like October’s Orionids, produced by debris shed from Comet 1P/Halley, and are extremely swift meteors, often leaving short-duration persistent trains. Peak activity occurs over several nights close to May 5, and observers seeking a challenge might wish to make use of the last hour or so of darkness on mornings around this date to obtain watch time on this elusive shower: many very experienced northern-hemisphere meteor-watchers have never seen an Eta Aquarid!
Active April 20-May 19
Radiant RA 16h 31m Dec -24o
16h 04m -24o
Active May 19-July
Radiant RA 17h 56m Dec -23o
17h 20m -20o
Continuing the near-ecliptic trickle of low activity through early summer, these two showers offer only low rates for observers willing to persevere with the permanently twilit skies. As with the earlier Virginids, the meteors can sometimes be long, slow and reasonably bright as they climb from the low southern sky.
Active July-August
Radiant RA 20h 44m Dec -15o
21h 00m -15o
July finally sees a significant upturn in overall meteor activity, including improved background sporadic rates. The Capricornids, active from early in the month, are a rather poorly-defined shower from the near-ecliptic region, with possible maxima on July 8, 15 and 26. The first two of these are favoured by an absence of moonlight in 2005, but observed rates are never likely to be higher than one or two per hour.
Active July-August
Radiant RA 21h 00m Dec +48o
Throughout July and August, a steady trickle of one or two meteors/hr is reported from an apparently stationary radiant near Deneb, high in the UK summer sky. In theory, meteor shower radiants should move eastwards by roughly a degree per day, thanks to Earth’s orbital motion, and there are therefore some doubts as to whether the Alpha Cygnids are a genuine shower, or simply the result of observers aligning sporadic activity to a radiant close to a conveniently bright star.
Late July brings us into the most substantial active meteor period for the summer, with the combined output of the Delta Aquarids, Alpha Capricornids, Iota Aquarids, Piscis Ustralids and Perseids making for productive watches as the skies begin to darken once again following the Summer Solstice. The Moon is at Last Quarter on July 28, and as it retreats further into the morning sky during early August, observers can look forward to some excellent watches, weather permitting.
Active July 15-August 20
Radiant RA 22h 36m Dec -17o
23h 04m +02o
The Delta Aquarids are the most productive of several showers with radiants south of tge Square of Pegasus, still rather low in British skies on a July-August night. The shower has two branches, the southern being the more active: peak for this branch is on July 28-29, and rather badly affected by moonlight. The northern branch, with its radiant near the ‘Water Jar’, is better-placed (higher in the sky) for UK observers, and peaks, favourably, on August 6-7 with the Moon well out of the way. Peak Zenithal Hourly Rate (ZHR, allowing for sky transparency and radiant elevation) for the Northern Delta Aquarids is about 10, perhaps corresponding to observed rates of 5-6 per hour under good conditions. Most Delta Aquarids are medium-velocity meteors in the magnitude +2 to +4 range; the shower is not particularly noted for an abundance of bright events.
Active July 15-August 20
Radiant RA 20h 36m Dec -10o
Although comparatively weak (ZHR 5), tge Alpha Capricornids are a distinctive shower, producing long, slow meteors which can sometimes be notably bright. Observers conducting watches in early August can expect to record one or two ‘Alpha Caps’ per hour, and the nominal peak on August 2-3 is well-placed with respect to moonlight - the Moon is New on August 5 and therefore won't interfere. The radiant is close to the wide naked-eye pair of Alpha and Beta Capricorni, fairly low in the southern sky on an August night.
Active July-August
Radiant RA 22h 10m Dec -15o
22h 04m -06o
Like the Delta Aquarids, a shower with a double radiant. At peak, on August 6-7, the Iota Aquarid radiants lie roughly 10 degrees east of those of the Delta Aquarids, and care must be taken to distinguish the two showers. Iota Aquarid meteors are mostly faint and quite swift.
Active July 15-August 20
Radiant RA 22h 40m Dec -30o
Further complicating the radiant profusion in the low summer sky, the Piscis Australids are a rather minor stream, producing slow, long meteors. The radiant’s low altitude from UK locations means that rather few of these are reported by BAA observers.
Active July 23-August 20
Radiant RA 03h 04m Dec +58o
Without doubt, the main attraction for meteor observers in summer 2005 will be the Perseids, at their best on the Friday night to Saturday morning of August 12-13. Peak is expected around 13h UT on August 12, during daylight for the British Isles, and observers watching late on Aug 11-12 should experience increasing activity towards dawn. Rates will be starting to decline late on Aug 12-13, but from a clear, dark location observers might still expect to see rates of a meteor per minute in the latter parts of the night as the shower radiant (near the Double Cluster on the Perseus/Cassiopeia border) climbs high into the eastern sky.
Perseid Radiant At 53oN
Local Time Altitude
21h 28.1o
22h 32.8o
23h 38.4o
00h 44.7o
01h 52.8o
02h 59.3o
03h 67.1o
Perseid activity is evident as early as the third week of July. In 2005, this low-activity part of the shower will be lost to strong moonlight. The good news, however, is that the main part of the shower, including its steady rise through the first 9 days or so of August, will be blessed with dark skies. Activity takes a marked ‘kick’ around August 8-9, and watches between this date and August 14-15, particularly, should be very rewarding. By the August 12-13 maximum, the Moon is at First Quarter, but sets well before midnight UT, leaving dark conditions for those parts of the night when the radiant is high in the sky.
The Perseids are associated with Comet 109P/Swift-Tuttle, which was last at perihelion in 1992. Enhanced activity accompanied that return, and was evident for several years, up to at least 1997. The 2002 Perseids - our most recent well-covered return of the shower - proved fairly ‘normal’, with a single sharp peak to ZHR ca. 100, and the usual slow rise to and steep decline from maximum.
Forecasts of slightly enhanced Perseid activity (resulting from recently-ejected material and an orbital resonance between the meteor stream and Jupiter) in 2004 may have been borne out by observations from eastern Europe. There is no expectation of anything unusual in 2005, but as always the shower requires careful scrutiny on all possible clear nights (and not just at maximum!).
The Perseids are well known for the abundance of fast, bright meteors close to their maximum. Perseid meteoroids enter the atmosphere at a velocity of 60 km/sec, and the resulting meteors often leave behind persistent ionisation trains.
The large numbers of bright events in the five-day interval centred on Perseid maximum makes this an excellent target for photography. Exposures, which can be with a static (undriven) camera, of 10-15 minutes’ duration, using ISO 400 film and a 50 mm or wideangle 28 mm lens at f/2.8 or faster, can capture meteors of magnitude 0 and brighter. Ideal aiming directions are about 20-30 degrees to one side of the radiant at 50 degrees altitude above the horizon - Cygnus in early evening, the Square of Pegasus later in the night, or towards the north celestial pole, for example.
Page last updated: 16/12/2005