Contents
- Introduction
- January to March
- April to June
- July to September
- October to December
- Tables
- Table 1 – Radiant diameter
- Table 2 – Error limits for the angular velocity
- Table 3 – Angular velocities
- Table 4 – Lunar phases for 2008
- Table 5 – Working List of Visual Meteor Showers
- Table 6 – Radiant positions during the year in α and δ
- Table 7 – Working List of Daytime Radio Meteor Streams
- Abbreviations
Introduction
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 Jeff Brower, David Entwistle, Roberto Gorelli and Jérémie
Vaubaillon for valuable discussions in respect of several potential events in
2008.
Welcome to the 2008 International Meteor Organization (IMO) Meteor
Shower Calendar. The meteor year ahead starts well for the stronger
showers, with moonless maxima for the Quadrantids, α-Centaurids,
η-Aquarids and δ-Aquarids, but things go somewhat awry in
August with the Perseids peaking near full Moon, while the Orionids in
October, the Leonids in November and the Geminids in December are even
worse-placed. However, the Draconid epoch should still be partly observable,
while the late October to early November spell, which may bring another
‘swarm’ enhancement from the Taurids, is Moon-free, as too is the Ursid
peak towards year’s end. 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 as many of you will appreciate, completed its most recent
thorough 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.
Consequently, more changes have been made this time, to amend some minor
inconsistencies in the 2007 version. Please be sure to use the information
here when preparing for your observing in 2008, as even some of the stronger
showers like the Perseids and Leonids have had minor adjustments made to their
radiant locations.
Apart from these 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, possibly
including some of those recently removed from the visual showers’ list. There is
also a set of 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 Streams. 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. 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 biggest change in the 2006 upgrade of the Visual Working List was the
removal of most of those minor near-ecliptic sources that previously seemed to
‘chase’ one another around the sky throughout the year, such as the Virginids of
February-March, and many of the July-August Aquarid showers. They were replaced
with a large, diffuse radiant area, whose size is taken to be roughly α =
30° by δ = 15° , centred around 12° east of the solar opposition point on
the ecliptic. Such a location names it as the ‘Antihelion Source’, abbreviated
as ‘ANT’. This has been done as it seems to give a better description of the
actual observed activity than the cluster of previous, often supposedly
variable, very minor sources in this part of the sky. At present, we think the
July-August α-Capricornids (CAP), and particularly the δ-Aquarids
(SDA), 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
A 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.
Quadrantids (QUA)
| Active: | January 1 – 5 |
| Maximum: | January 4 – 06h40m UT (λsol = 283° 16) |
| ZHR = | 120 (can vary ~ 60 – 200) |
| Radiant: | α = 230° ; δ = +49° |
| Radiant drift: | see Table 6 |
| vinf = | 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) |
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)
| Active: | January 28 – February 21 |
| Maximum: | February 8 17h UT (λsol = 319° 2) |
| ZHR = | variable; usually ~ 5 but may reach 25+ |
| Radiant: | α = 211° δ = -59° |
| Radiant drift: | see Table 6 |
| vinf = | 56 km/s; r = 2.0 |
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)
| Active: | February 25 – March 22 |
| Maximum: | March 13 (λsol = 353° ) |
| ZHR = | 4 |
| Radiant: | α = 239° δ = -50° |
| Radiant drift: | see Table 6 |
| vinf = | 56 km/s; r = 2.4 |
| TFC: | α = 225° δ = -26° and α = 215° δ = -45° (β < 15° S) |
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.
April to June
Meteor 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-Aquarids 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.
π-Puppids (PPU)
| Active: | April 15 – 28 |
| Maximum: | April 23 10h UT (λsol = 33° 5 – but see below) |
| ZHR = | periodic – up to around 40 |
| Radiant: | α = 110° δ = -45° |
| Radiant drift: | see Table 6 |
| vinf = | 18 km/s r = 2.0 |
| TFC: | α = 135° δ = -55° and α = 105° δ = -25° (β < 20° N) |
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.
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-Aquarids (ETA)
| Active: | April 19 – May 28 |
| Maximum: | May 5 18h UT (λsol = 45° 5) |
| ZHR = | 70+ (periodically variable ~ 40 – 85) |
| Radiant: | α = 338° δ = -01° |
| Radiant drift: | see Table 6 |
| vinf = | 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 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.
ε-Lyrids (ELY)
| Active: | May 3 – 12 |
| Maximum: | May 8 18h UT (λsol = 48° 4) |
| ZHR = | 3 |
| Radiant: | α = 287° δ = +44° |
| Radiant drift: | see Table 6 |
| vinf = | 44 km/s; r = 3.0 |
| TFC: | α = 325° δ = +40° or α = 285° δ = +15° and |
| α = 260° δ = +30° (β > 10° S) |
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.
June Boötids (JBO)
| Active: | June 22 – July 2 |
| Maximum: | June 27 02h30m UT (λsol = 95° 7) |
| ZHR = | variable: 0 – 100+ |
| Radiant: | α = 224° δ = +48° |
| Radiant drift: | see Table 6 |
| vinf = | 18 km/s; r = 2.2 |
| TFC: | α = 156° δ = +64° and α = 289° δ = +67° (β = 25° – 60° N) |
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 September
With 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-Aquarids 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.
Piscis Austrinids (PAU)
| Active: | July 15 – August 10 |
| Maximum: | July 27 (λsol = 125° ) |
| ZHR = | 5 |
| Radiant: | α = 341° δ = -30° |
| Radiant drift: | see Table 6 |
| vinf = | 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 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-Aquarids (SDA)
| Active: | July 12 – August 19 |
| Maximum: | July 27 (λsol = 125° ) |
| ZHR = | 20 |
| Radiant: | α = 339° δ = -16° |
| Radiant drift: | see Table 6 |
| vinf = | 41 km/s; r = 3.2 |
| TFC: | α = 255° to 000° δ = 00° to +15° |
| choose pairs separated by about 30° in α (β < 40° N) |
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-Aquarids, and the
Northern and Southern δ-Aquarids, 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)
| Active: | July 3 – August 15 |
| Maximum: | July 29 (λsol = 127° ) |
| ZHR = | 4 |
| Radiant: | α = 307° δ = -10° |
| Radiant drift: | see Table 6 |
| vinf = | 23 km/s; r = 2.5 |
| TFC: | α = 255° to 000° δ = 00° 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 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 sugges