Contents
compiled by Alastair McBeath. Based on information in
IMO Monograph No. 2: Handbook for Visual Meteor Observers, edited by
Jürgen Rendtel, Rainer Arlt and Alastair McBeath, IMO, 1995, as amended
by the commentaries in WGN 34:3 (June 2006), pp. 71-84,
with subsequent corrections, plus additional material extracted from reliable
data analyses produced since. Particular thanks are due to Rainer Arlt, David
Asher, Jeff Brower, David Entwistle, Esko Lyytinen and Jérémie Vaubaillon
for valuable discussions in respect of several events in 2009.
Introduction
Welcome to the 2009 International Meteor Organization (IMO) Meteor Shower
Calendar. Of the more active annual showers, the Quadrantids, Lyrids,
η- and Southern δ-Aquariids, Orionids, Leonids and Geminids are
best placed with regards the Moon, along with the occasionally stronger
Ursids in December. Of greatest potential interest for what they may produce
are the η-Aquariids and Orionids (which should be near their theoretical
12-year ZHR peaks in 2009, the Orionids having already produced
unexpectedly strong activity in both 2006 and 2007, albeit apparently
not from this cause), the moonlit Perseids, which may show an additional
maximum again this year, and the Leonids, which could yield ZHRs in the
100+ category, maybe (if we are very fortunate) bordering on near-storm
levels again! For radio observers, and hopeful daylight fireball enthusiasts,
there is the chance of another Taurid ‘swarm’ return in June-July. There are
minor showers to be monitored as well, and ideally, meteor observing should
be carried out throughout the year to check on all the established sources,
and for any new ones. We appreciate this is impractical for most people, so
the Shower Calendar has been helping to highlight times when a particular
effort might most usefully be employed since 1991.
The heart of the Calendar is the Working List of Visual Meteor Showers,
Table 5, which had its most recent overhaul by IMO analysts in 2006,
to help it remain the single most accurate listing available anywhere
today for naked-eye meteor observing. Of course, for all its accuracy,
it is a Working List, so is continually subject to further checks
and corrections, based on the best data we have, so it is always as well
to check the information here fully, before going out to observe (and please
notify us if you find any anomalies!).
Apart from the visually-observable showers, there are many others weakly
active throughout the year which only still-imaging, video, radar or
telescopic observations can separate from the omnipresent background
sporadics, as well as showers with radiants too near the Sun to be observed
by the various optical methods, which can be detected only by forward-scatter
radio or radar observations. Some of these showers are given in Table 7,
the Working List of Daytime Radio Meteor Showers. The IMO’s aims are to
encourage, collect, analyze, and publish combined meteor data obtained from
sites all over the globe, to help better our understanding of the meteor
activity detectable from the Earth’s surface. Thus, we encourage these more
specialist forms of observing too, so all meteor workers, wherever you are
and whatever methods you use to record meteors, should follow the standard
IMO observing guidelines when compiling your information, and submit those
data promptly to the appropriate Commission for analysis (contact details
are at the end of the Calendar). Thanks to the efforts of the many IMO
observers worldwide since 1988 that have done this, we have been able to
achieve as much as we have to date, including keeping the shower listings
vibrant. This is not a matter for complacency however, since it is solely
by the continued support of many people across the planet that our steps
towards constructing a better and more complete picture of the near-Earth
meteoroid flux can proceed.
Although timing predictions are included below on all the more active
night-time and daytime shower maxima, as reliably as possible, it is
essential to understand that in many cases, such maxima are not known
more precisely than to the nearest 1° of solar longitude (even less
accurately for the daytime radio showers, which have received little
regular attention until quite recently). In addition, variations in
individual showers from year to year mean past returns are only a guide
as to when even major shower peaks can be expected. The information
given here may be updated after the Calendar is published, so be sure
to watch for alerts on the Internet (including on IMO-News) and in WGN,
the IMO’s bimonthly journal. Some showers are known to show particle
mass-sorting within their meteoroid streams, so the radar, radio,
still-imaging, telescopic, video and visual meteor maxima may occur at
different times from one another, and not necessarily just in those
showers. The majority of data available are for visual shower maxima,
so this must be borne in mind when employing other observing techniques.
However and whenever you are able to observe, we wish you all a most
successful year’s work and very much look forward to receiving your
data. Clear skies!
Antihelion Source
The Antihelion Source (ANT) is a large, roughly oval area with a size of
30° in right ascension and 15° in declination, centred about 12°
east of the solar opposition point on the ecliptic, hence its name. It is
not a true shower at all, but is rather a region of sky in which a
number of variably, if weakly, active minor showers have their radiants.
Until 2006, attempts were made to define specific showers within this
complex, but this often proved very difficult for visual observers to
achieve. IMO video results from the last decade have shown why, because
even instrumentally, it was impossible to usefully define distinct
radiants for many of the showers here! Consequently, we currently believe
it is best for observers to simply identify meteors from these showers
as coming from the ANT alone. At present, we think the July-August
α-Capricornids (CAP), and particularly the Southern δ-Aquariids
(SDA; because their stream parameters are rather different from the average
ANT orbits), should remain discretely observable visually from the ANT,
so they have been retained in the Working List, but time and plenty of
observations will tell, as ever. Later in the year, the strength of
the twin Taurid showers (STA and NTA) means the ANT should be considered
inactive while the Taurids are underway, from late September to late
November. To assist observers, a set of charts showing the location for
the ANT and any other nearby shower radiants is included here, to compliment
the numerical positions of Table 6, while comments on the ANT’s location
and likely activity are given in the quarterly summary notes.
January to March
First quarter Moon favours the northern-hemisphere Quadrantids in early
January, but the probable southern-hemisphere α-Centaurid peak, due
around 23h UT on February 7, is too close to full Moon on February 9.
Mid-March brings an equally poor minor γ-Normid return for similarly
southern places, likely at maximum sometime between March 10-17,
perhaps most plausibly around March 13. 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 λo ~ 286° -293° (January 6
to 13 in 2009, ruined by full 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, enjoys a new Moon for its
potential core period, January 20-27. Theoretical approximate timings
(rounded to the nearest hour) for the daytime radio shower maxima this
quarter are: Capricornids/Sagittariids – February 1, 9h UT; and
χ-Capricornids – February 13, 10h 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.
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Quadrantids (QUA)
| Active: | January 1-5 |
| Maximum: | January 3 12h50m UT (λo = 283° 16) |
| ZHR = | 120 (can vary ~ 60-200) |
| Radiant: | α = 230° δ = +49° |
| Radiant drift: | see Table 6 |
| v∞ = | 41 km/s; r = 2.1 at maximum (but variable) |
| TFC: | α = 242° δ = +75° and α = 198° δ = +40° (β > 40° N) |
| IFC: | before 0h local time α = 150° δ = +70° |
| ∞ after 0h local time α = 180° δ = +40° and α = 240° δ = +70° (β > 40° N) |
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The waxing crescent Moon will set near local midnight for the maximum of
the Quadrantids at northern hemisphere sites, from many of which, the
shower’s radiant is circumpolar, in northern Boötes. As this area
attains a useful elevation only after local midnight, rising higher in
the sky towards morning twilight, this is excellent news. However, the
expected peak’s timing falls poorly for land-based observers, except
for those in the extreme western areas of North America, on islands in
the North Pacific Ocean, and the extreme east of Russia. 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 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
preliminary results from 2008 persisted for more than two hours at close
to their best, with the maximum itself centred around three to four hours
later than anticipated. 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 2009 would fall ideally for sites from Europe east to
central Asia. Oddly, in 2008, there seemed to be two possible radio
Quadrantid peaks, but the first was apparently about six hours before
the visual one, during an apparent rates-plateau ahead of the main maximum
in the visual data.
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.
April to June
Meteor activity picks up towards the April-May boundary, with excellently
moonless shower peaks in late April from the Lyrids and π-Puppids,
and even the η-Aquariids in early May survive the waxing gibbous Moon.
The minor η-Lyrids will likely pass unobserved however, with their
low-activity maximum on May 9 coincident with full 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 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, 9h; δ-Piscids – April 24,
9h; ε-Arietids – May 9, 8h; May Arietids – May 16,
9h; o-Cetids – May 20, 8h; Arietids – June 7, 11h;
ζ-Perseids – June 9, 11h; β-Taurids – June 28, 10h.
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.
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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 16) are not too favourable this year, with last quarter
Moon rising around midnight. Conditions are rather better for possible
June Boötid hunting.
Taurid ‘swarm’ return: Work by David Asher has suggested the
possibility of another return of the Taurid meteoroid ‘swarm’ during
June 2009. If so, it may be detectable as an increased radio meteor
flux during the ζ-Perseids or the β-Taurids, both of
which are probably associated with the Taurid Complex of meteor showers,
asteroids and comets. Each of the last three predicted night-time ‘swarm’
events during the October-November Taurids, in 1995, 1998 and 2005
produced noticeably different activity to normal. In 2005, and most
impressively of the three, this included increased Taurid ZHRs and a
lot of shower fireballs from late October to mid-November. Another
night-time ‘swarm’ return was due in late 2008, still to come when
this Calendar text was prepared. However, previous theoretical daytime
‘swarm’ returns in 1995, 1999 and 2002 have proven elusive, with
nothing very remarkable found in the June-July radio results for any of
those years that might be definite signs of such a return. The encounter
geometry in 2009 June is expected to be similar to that in 2005
October-November, so any repeat of comparable activity may give the
best chance of such a daytime-sky recovery, if it happens. The most
likely time for anything to be detected is probably about 5- days
before the β-Taurid peak, thus around June 20-23, but its
potential timing and strength are unknown. There is also the chance
that if an increased fireball flux takes place, there may be some
daylight fireballs reported visually, though of course these cannot
be deliberately watched for.
Lyrids (LYR)
| Active: | April 16-25 |
| Maximum: | April 22 11h UT (λo = 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 |
| v∞ = | 49 km/s; r = 2.1 |
| TFC: | α = 262° δ = +16° and α = 282° δ = +19° (β > 10° S) |
The λo = 32° 32 timing given above is the ‘ideal’ maximum found
in the most detailed examination of the Lyrids in modern times,
published in 2001 by Audrius Dubietis and Rainer Arlt, drawing on
IMO results from 1988-2000. However, the maximum time was
found to be variable from year to year between λo = 32° 0-32° 45
(equivalent to 2009 April 22, 3h to 14h UT). Activity was
discovered to be variable too. A peak at the ideal time produced the
highest ZHRs, ~ 23, while the further the peak happened from this,
the lower the ZHRs were, down to ~ 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.) The mean peak ZHR was 18
over the thirteen years examined. While generally thought of as having
a short, quite sharp, maximum, this latest work revealed the shower’s
peak length was inconstant too. Using the interval that ZHRs were
above half the maximum amount, the Full-Width-Half-Maximum time, a
variation of from 14.8 hours (in 1993) to 61.7 hours (in 2000)
was detected, with a mean value of 32.1 hours. The very best rates
are normally achieved for just a few hours however. One other aspect
of the analysis confirmed data from earlier in the 20th century,
that occasionally, as their highest rates occurred, the Lyrids
produced a short-lived increase in 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 take place.
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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 the
shower is suitable for all forms of observation. As its radiant
rises during the night, watches can be usefully carried out from
about 22h30m local time onwards from mid-northern sites, but
only from well after midnight from the mid-southern hemisphere.
The waning crescent Moon will rise too late in the night in the
northern hemisphere to cause any problems, and will be just a
minor distraction further south on April 22. If the ideal maximum
time recurs, it should be best seen from sites across the central
to eastern Pacific Ocean, and the extreme west of North America,
but other maximum times are perfectly possible, as noted above.
π-Puppids (PPU)
| Active: | April 15-28 |
| Maximum: | April 23 16h UT (λo = 33° 5) |
| ZHR = | periodic – up to around 40 |
| Radiant: | α = 110° δ = -45° |
| Radiant drift: | see Table 6 |
| v∞ = | 18 km/s; r = 2.0 |
| TFC: | α = 135° δ = -55° and α = 105° δ = -25° (β < 20° N) |
Activity has only been detected from this source since 1972, with
notable, short-lived, shower maxima of around 40 meteors per hour
in 1977 and 1982, both years when its parent comet,
26P/Grigg-Skjellerup 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 most recent perihelion in 2008 March produced
nothing meteorically significant that April, but lunar circumstances
in 2008 were poor, and faint-meteor activity (which was predicted
as likely in advance) could have been missed. There were no
predictions for activity in force for 2009 when this Calendar was
prepared. 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. April’s new Moon on the 25th creates perfect viewing
circumstances this year. Covering whatever happens is important in
all years, even if that is to report no obvious activity, as past
datasets on the shower have typically been very patchy. 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.
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η-Aquariids (ETA)
| Active: | April 19-May 28 |
| Maximum: | May 6 0h UT (λo = 45° 5 |
| ZHR = | 85 (periodically variable – ~ 40-85) |
| Radiant: | α = 338° δ = -01° |
| Radiant drift: | see Table 6 |
| v∞ = | 66 km/s; r = 2.4 |
| TFC: | α = 319° δ = +10° and α = 321° δ = -23° (β < 20° S) |
A fine, rich shower 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 could be around their very best in 2009,
according to this idea. However, activity in 2007 seemed unexpectedly
weaker than normal (peak ZHRs maybe only ~ 50), which combined with
the unexpectedly strong Orionid returns in October 2006 and 2007,
add an extra degree of uncertainty over what may happen from the
η-Aquariids this year. The waxing gibbous Moon on May 6 will set
in time to still leave most of the best-visible interval viable for
visual watchers well south of the equator, at least. 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 Boötids (JBO)
| Active: | June 22-July 2 |
| Maximum: | June 27 08h30m UT (λo = 95° 7 |
| ZHR = | variable – 0-100+ |
| Radiant: | α = 224° δ = +48° |
| Radiant drift: | see Table 6 |
| v∞ = | 18 km/s; r = 2.2 |
| TFC: | α = 156° δ = +64° and α = 289° δ = +67° (β = 25° -60° N) |
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,
the shower’s start date was 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, though that in 1921 was very uncertainly
recorded. 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. Its most recent perihelion passage was in 2008 September.
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 2009 at the time of writing, but conditions for checking
are very favourable from the mid-northern latitudes where the radiant
is best seen, with an early-setting waxing crescent Moon. The prolonged
– in some places continuous – mid-northern 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 September
The Antihelion Source is the chief focus for visual attention for most
of July, as its radiant area moves steadily through eastern Sagittarius,
then 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, and for a
time in mid-month even < 1! 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 reasonably 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, badly moonlit, Perseids, and the almost Moon-free
κ-Cygnid peak, 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. The minor September Perseids lose out to the waning gibbous
Moon for their likely maximum around September 9, but part of the
probable very weak δ-Aurigid peak later in the month should
be clear enough of the Moon to observe.
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For most of September, ANT
rates continue from their radiant in Pisces, albeit with ZHRs
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 due near August 25, 10h UT, albeit not found in recent
radio results), and a tricky visual shower, the Sextantids. Their
maximum is expected on September 27, around 10h UT, but may
possibly occur a day earlier. In 1999 a strong return was detected
at λo ~ 186° equivalent to 2009 September 29, 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.
The waxing gibbous Moon creates no additional difficulties for
visual observers hoping to catch some Sextantids in the pre-dawn
of late September, though radiant-rise is less than an hour before
sunrise in either hemisphere.
Perseids: Although the major northern hemisphere Perseids are badly
affected by the last quarter Moon near their best this year, there is
the possibility they may produce more than one peak again, perhaps also
with somewhat increased rates. The usual maximum is due around August 12,
17h30m-20h00m UT (λo = 140° 0-140° 1), but Esko Lyytinen
suggests we may encounter the 1610 Perseid trail earlier on August 12,
around 9h00m UT (λo = 139° 661). This could produce activity
additional to the normal Perseid ZHRs then of a few tens, maybe up to a
hundred, probably with a fairly normal magnitude distribution, or perhaps
marginally brighter. He further suggests that rates overall could be
enhanced above usual by the relative proximity of the annual stream’s
core, most likely at other times on August 12 ahead of the normal peak.
The 19th century trail should pass roughly 0.003 astronomical units
inside the Earth’s orbit at λo = 139° 499, so around 5h UT on
August 12, though it may add less than 10 to the ZHR at that point.
Naturally, information to verify what takes place will be very valuable
despite the Moon, so visual observers are encouraged to try to follow as
much of what happens over the possible Perseid maxima as practical.
Piscis Austrinids (PAU)
| Active: | July 15-August 10 |
| Maximum: | July 28 (λo = 125° ) |
| ZHR = | 5 |
| Radiant: | α = 341° δ = -30° |
| Radiant drift: | see Table 6 |
| v∞ = | 35 km/s; r = 3.2 |
| TFC: | α = 255° to 000° δ = 00° to +15° |
| choose pairs separated by about 30° in α (β < 30° N) |
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 be due simply to the large amount of northern hemisphere
summer data, and the almost complete lack of southern hemisphere winter
results, on it. The shower 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. First quarter Moon for the probable maximum
will set between 22h-00h (its setting time is progressively later
for places further south).
Southern δ-Aquariids (SDA)
| Active: | July 12-August 19 |
|---|---|
| Maximum: | July 28 (λo = 125° ) |
| ZHR = | 20 |
| Radiant: | α = 339° δ = -16° |
| Radiant drift: | see Table 6 |
| v∞ = | 41 km/s; r = 3.2 |
| TFC: | α = 255° to 0° δ = 0° to +15° |
| choose pairs separated by about 30° in α (β < 40° N) |
Like the PAU and ANT, 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, and the SDA enjoys
identical dark-sky conditions in the second half of the nights near
its maximum to the PAU. Its peak may not be quite so sharp as the
single date here might imply, with perhaps similar ZHRs from
July 28-30. Its rates have been suspected of some variability
at times too, though not in the more recent investigations.
α-Capricornids (CAP)
| Active: | July 3-August 15 |
| Maximum: | July 30 (λo = 127° ) |
| ZHR = | 4 |
| Radiant: | α = 307° δ = -10° |
| Radiant drift: | see Table 6 |
| v∞ = | 23 km/s; r = 2.5 |
| TFC: | α = 255° to 0° δ = 0° to +15° |
| choose pairs separated by about 30° in α (β < 40° N) | |
| IFC: | α = 300° δ = +10° (β > 45° N) |
| α = 320° δ = -05° (β=0° to 45° N) | |
| α = 300° δ = -25° (β < 0° ) |
The CAP 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. The slightly slower speed of the
α-Capricornids compared to the ANT may help distinguish them
from the ecliptical background.} 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 30-31 this year. The
waxing gibbous Moon sets somewhat later for this interval than for
the PAU and SDA, even so, between roughly 23h-3h (again,
later moonsets occur at more southerly latitudes).
κ-Cygnids (KCG)
| Active: | August 3-25 |
| Maximum: | August 17 (λo = 145° ) |
| ZHR = | 3 |
| Radiant: | α = 286° δ = +59° |
| Radiant drift: | see Table 6 |
| v∞ = | 25 km/s; r = 3.0 |
| IFC: | α = 330° δ = +60° and α = 300° δ = +30° (β > 20° N) |
The waning crescent Moon creates no problems for viewing the expected
κ-Cygnid peak this year from northern hemisphere sites, where
the shower is chiefly accessible. Its r-value suggests telescopic
and video observers may benefit from the shower’s presence, but visual
and photographic workers should note that occasional slow fireballs
from this source have been reported too. The almost stationary radiant
results from its close proximity to the ecliptic north pole in Draco.
There has been some suggestion of a variation in its activity at times,
perhaps coupled with a periodicity in fireball sightings, but more data
are needed on a shower that is often ignored in favour of the major
Perseids during August.
Aurigid Showers
α-Aurigids (AUR)
| Active: | August 25-September 8 |
| Maximum: | September 1 01h UT (λo = 158° 6) |
| ZHR = | 7 |
| Radiant: | α = 84° δ = +42° |
| Radiant drift: | see Table 6 |
| v∞ = | 66 km/s; r = 2.6 |
| TFC: | α = 052° δ = +60° ; α = 043° δ = +39° and |
| α = 023° δ = +41° (β > 10° S) |
δ-Aurigids (DAU)
| Active: | September 18-October 10 |
| Maximum: | September 29 (λo = 186° ) but see text |
| ZHR = | 3 |
| Radiant: | α = 82° δ = +49° |
| Radiant drift: | see Table 6 |
| v∞ = | 64 km/s; r = 2.9 |
| TFC: | As AUR |
Along with the September Perseids (SPE), these essentially northern hemisphere
showers appear to be part of a series of poorly-observed sources with
radiants around Aries, Perseus, Cassiopeia and Auriga, active from late
August into October. IMO investigations using data collected since
1986 have suggested there are at least three showers which repeat
annually, of which the AUR are the marginally stronger. 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.
The AUR 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! While badly moonlit, the
first predicted outburst happened roughly as expected in 2007,
producing short-lived EZHRs of ~ 130 for western North America,
with many bright meteors. Radio data suggested there was a ‘tail’
to that event where more faint meteors continued for maybe an hour
after the strongest peak, but visual observers could not confirm this,
pobably due to the moonlit sky. Both Aurigid radiants reach useful
elevations after 23h-0h local time, and this year conditions
are reasonably good for the AUR peak, with the waxing gibbous Moon
setting between midnight and 2h on August 31-September 1.
No predictions for stronger activity had been made when this text
was written, however.
The DAU name has recently been adopted for the weaker segment of
what may be a single shower, as its radiant and activity follow
along directly from those of the September Perseids. At present,
the showers should be treated as distinct in your observations.
The DAU seem to give a weak and very ill-defined maximum between
roughly λo = 181° -191° (2009 September 24 to October 4).
September 29 is simply the approximate middle of this peak interval,
with a waxing gibbous Moon this year that will set before local
midnight north of the equator. The later part of this possible
maximum spell will see increasing moonlight problems as full Moon
approaches on October 4.
October to December
An excellent final quarter to the year beckons, with maxima from the
all more active showers splendidly moonless. Only three less active
shower peaks are lost to the bright Moon, those of the Southern
Taurids, σ-Hydrids (December 12) and Coma Berenicids
(probably around December 29, but see the notes below). The period
near the possible Puppid-Velid early-December maximum/reference date,
December 7, is also badly Moon-affected. The ANT starts the quarter
effectively inactive in favour of the Taurids, but as the Taurids fade
away, we should be able to again distinguish them from the sporadics as
the sole ecliptical background from November 26, with a radiant centre
position in eastern Taurus. During December, this centre 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.
October 5/6 meteors: Short-lived video outbursts were recorded
in 2005 and 2006 by European observers, with activity from a
north-circumpolar radiant near the ‘tail’ of Draco, around
α ~ 165° δ ~ +78° on October 5/6.
The 2005 event (only) was recorded very weakly by radio, but no
visual results confirmed either occurrence, and no recurrence was
reported in 2007. The 2008 repeat time was still to come when
this was written. As the 2005/2006 events happened between
λo ~ 192° 55-192° 64, this would be equivalent to
2009 October 5, 19h20m-21h30m UT, poorly timed for
observing thanks to the bright Moon, full on October 4. The
meteors showed an atmospheric velocity of ~ 45-50 km/s.
If the active interval keeps to the same time, it would be
best observed by video from Europe east across all of Asia.
Coma Berenicids (COM): As noted in the 2008 Shower Calendar,
IMO single-station video data prepared just be