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(meteorobs) IMO 2000 Meteor Shower calender
International Meteor Organization
2000 Meteor Shower Calendar (Net Version)
=========================================
compiled by Alastair McBeath and Rainer Arlt
based on information in IMO Monograph No.2: Handbook for Visual Meteor
Observers, edited by Juergen Rendtel, Rainer Arlt and Alastair McBeath,
IMO, 1995, and additional material extracted from data analyses produced
since. Layout by Andre Knoefel.
Introduction
------------
Welcome to the 2000 International Meteor Organization (IMO) Meteor Shower
Calendar. The year promises many Moon-free major showers (except the
Lyrids, Perseids, Orionids and Geminids), and the Leonids may produce high
to storm rates in November. Of especial interest is the chance to see what
the June Bootids produce in late June after their unexpected outburst in
1998. Do not forget that monitoring of meteor activity should ideally be
carried on throughout the rest of the year too, however! We appreciate that
this is not practical for many observers, and this Calendar was devised as
a means of helping observers deal with reality by highlighting times when a
particular effort may most usefully be employed. Although we include to-
the-hour predictions for all the more active night-time and daytime shower
maxima, based on the best available data, please note that in many cases,
such maxima are not known more precisely than to the nearest 1deg of solar
longitude (even less accurately for the daytime radio showers, which have
only recently begun to receive regular attention again). In addition,
variations in individual showers from year to year mean past returns are at
best only a guide as to when even major shower peaks can be expected, plus
as some showers are known to show particle mass-sorting within their
meteoroid streams, the radio, telescopic, visual/video and photographic
meteor maxima may occur at different times from one another, and not
necessarily just in these showers. The majority of data available are for
visual shower maxima, so this must be borne in mind when employing other
observing techniques.
The heart of the Calendar is the Working List of Visual Meteor Showers,
thanks to regular updating from analyses using the IMO's Visual Meteor
Database, the single most accurate listing available anywhere today for
naked-eye meteor observing. Even this can never be a complete list of all
meteor showers, since there are many showers which cannot be properly
detected visually, and some which only photographic, radar, telescopic, or
video observations can separate from the background sporadic meteors,
present throughout the year.
The IMO's aims are to encourage, collect, analyze, and publish combined
meteor data obtained from sites all over the globe in order to further our
understanding of the meteor activity detectable from the Earth's surface.
Results from only a few localized places can never provide such total
comprehension, and it is thanks to the efforts of the many IMO observers
worldwide since 1988 that we have been able to achieve as much as we have
to date. This is not a matter for complacency, however, since it is solely
by the continued support of many people across the whole world that our
steps towards constructing a better and more complete picture of the near-
Earth meteoroid flux can proceed. This means that all meteor workers,
wherever they are and whatever methods they use to record meteors, should
follow the standard IMO observing guidelines when compiling their
information, and submit their data promptly to the appropriate Commission
for analysis.
Visual and photographic techniques remain popular for nightly meteor
coverage (weather permitting), although both suffer considerably from the
presence of moonlight. Telescopic observations are much less popular, but
they allow the fine detail of shower radiant structures to be derived, and
they permit very low activity showers to be accurately detected. Video
methods continue to be dynamically applied as in the last few years, and
are starting to bear considerable fruit. These have the advantages, and
disadvantages, of both photographic and telescopic observing, but are
increasing in importance. Radio receivers can be utilized at all times,
regardless of clouds, moonlight, or daylight, and provide the only way in
which 24-hour meteor observing can be accomplished for most latitudes.
Together, these methods cover virtually the entire range of meteoroid
sizes, from the very largest fireball-producing events (using all-sky
photographic patrols or visual observations) through to tiny dust grains
producing extremely faint telescopic or radio meteors.
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!
January to March
----------------
The year's first quarter brings several low activity showers, including the
diffuse ecliptical stream complex of the Virginids, active from late
January to mid-April. Both major showers, the northern-hemisphere
Quadrantids and the southern-hemisphere alpha-Centaurids are excellently-
placed with regard to the Moon this year. The minor delta-Cancrids are lost
in the near-full Moon glare in January, but the weak delta-Leonids in late
February and the gamma-Normids in mid-March fare better. Daylight radio
peaks are theoretically due from the Capricornids/Sagittarids around 02h UT
on February 2, and the chi-Capricornids on February 14, around 03h UT.
Recent radio results suggest the Cap/Sgr peak may fall 2-3 days later than
this however, while no significant enhancement in radio rates was found
near the expected chi-Capricornid peak between 1994-1999. As both showers
have radiants <10deg-15deg west of the Sun at maximum, they cannot be
regarded as visual targets even from the southern hemisphere.
Quadrantids
-----------
Active: January 1-5; Maximum: January 4, 05h UT (lambda = 283.16deg);
ZHR = 120 (can vary around 60-200);
Radiant: alpha = 230deg, delta = +49deg, Radiant drift: see Table 6;
V = 41 km/s; r = 2.1 at maximum, but variable;
TFC: alpha = 242deg, delta = +75deg and
alpha = 198deg, delta = +40deg (beta> 40deg N).
PFC: before 00h local time alpha = 150deg, delta = +70deg;
after 00h local time alpha = 180deg, delta = +40deg and
alpha = 240deg, delta = +70deg (beta > 40deg N).
The year opens with a superb return of the Quadrantids for northern
hemisphere observers, as the Moon is just two days before new on January 4.
Since the shower's radiant is in northern Bootes, it is circumpolar for
many northern locations, but it attains a useful elevation only after local
midnight or so, and gets higher towards morning twilight. 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 locations.
The maximum time given above is based on the best-observed return of the
shower ever analyzed, from IMO 1992 data, confirmed by radio results in
1996, 1997 and 1999. A repeat of this time in 2000 would favor sites from
Europe to the east coast of North America. The peak itself is normally
short-lived, and can be easily missed in just a few hours of poor winter
weather in the north, 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!
Past observations have suggested the radiant is very diffuse away from the
maximum, contracting notably during the peak itself, although this may be a
result of the very low activity normally seen away from the hours near
maximum. Photographic and video observations from January 1-5 would be
particularly welcomed by those investigating this topic, using the PFCs and
TFCs given above, along with telescopic and visual plotting results.
alpha-Centaurids
----------------
Active: January 28-February 21;
Maximum: February 8, 16h UT (lambda = 319.2deg);
ZHR = variable, usually around 6, but may reach 25+;
Radiant: alpha = 210deg, delta = -59deg, Radiant drift: see Table 6
V = 56 km/s; r = 2.0.
The alpha-Centaurids are one of the main southern hemisphere high points in
the opening months of the year, producing many very bright, even fireball-
class, objects (meteors of at least magnitude -3). Their peak ZHR is
normally around 5-10, but in 1974 and again in 1980, bursts of only a few
hours' duration yielded activity closer to 20-30. As we have no means of
telling when another such event might happen, photographic, video and
visual observers are urged to be alert, especially this year, as the Moon
is new just three days before their maximum. Thanks to their brilliance,
even a normal alpha-Centaurid return is worth looking out for, and almost
one-third leave fine persistent trains after them. The radiant is nearly
circumpolar for much of the sub-equatorial inhabited Earth, and is at a
useful elevation from late evening onwards.
delta-Leonids
-------------
Active: February 15-March 10; Maximum: February 25 (lambda = 336deg);
ZHR = 2;
Radiant: alpha = 168deg, delta = +16deg, Radiant drift: see Table 6;
V = 23 km/s; r = 3.0;
TFC: alpha = 140deg, delta = +37deg and
alpha = 151deg, delta = +22deg (beta > 10deg N);
alpha = 140deg, delta = -10deg and
alpha = 160deg, delta = 00deg (beta < 10deg N).
This minor shower is probably part of the early Virginid activity. Rates
are normally low, and its meteors are predominantly faint, so it is a prime
candidate for telescopic investigation. Visual observers must make very
accurate plots of the meteors to distinguish them from the nearby Virginids
and the sporadics. Northern hemisphere sites have a distinct advantage for
covering this stream, especially this year as the waning gibbous Moon will
rise around or after midnight at the peak for sites north of 35deg N
latitude. Southern hemisphere watchers should not ignore the stream, as
they are better-placed to note many of the other Virginid radiants, but
with moonrise as early as 22h30m at 35deg S latitude on February 25,
conditions are not ideal. At least the delta-Leonid radiant in mid-Leo is
well on view for most of the night near the peak.
gamma-Normids
-------------
Active: February 25-March 22; Maximum: March 13 (lambda = 353deg);
ZHR = 8;
Radiant: alpha= 249deg, delta= -51deg, Radiant drift: see Table 6;
V = 56 km/s; r = 2.4;
TFC: alpha = 225deg, delta= -26deg and
alpha = 215deg, delta= -45deg (beta < 10deg S).
gamma-Normid meteors are 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 is normally quite sharp, with ZHRs of
3+ 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 reported in the past. Post-midnight watching yields best
results, when the radiant is rising to a reasonable elevation from southern
hemisphere sites. First quarter Moon on March 13 is thus excellent news, as
it will set before midnight. All forms of observation can be carried out
for the shower, though most northern observers will see nothing from it.
April to June
-------------
Meteor activity picks up towards the April-May boundary, with showers like
the Lyrids (maximum expected between April 21, 22h UT to April 22, 05h UT),
pi- Puppids (peak around April 23, 09h UT) and eta-Aquarids. Both former
sources suffer from bright waning gibbous moonlight this year. During May
and June, most of the activity is in the daytime sky, with six shower peaks
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, sensible activity calculations cannot be carried
out from such observations. For radio observers, the expected UT maxima for
these showers are as follows:
April Piscids - April 20, 02h;
delta-Piscids - April 24, 01h;
epsilon-Arietids - May 9, 00h;
May Arietids - May 16, 01h;
o-Cetids - May 20, 00h;
Arietids - June 7, 03h;
zeta-Perseids - June 9, 03h;
beta-Taurids - June 28, 02h.
Some signs of most of these peaks were found in data from 1994-1998, except
the April Piscids and May Arietids. The ecliptical complexes continue with
some late Virginids and the best from the minor Sagittarids in May-June.
Visual observers hoping to see any possible June Lyrid peak this year on
June 15 will be severely hampered by full Moon.
eta-Aquarids
------------
Active: April 19-May 28; Maximum: May 5, 17h UT (lambda = 45.5deg);
ZHR = 60 (occasionally variable);
Radiant: alpha = 338deg, delta= -01deg, Radiant drift: see Table 6;
V = 66 km/s; r = 2.7;
TFC: alpha = 319deg, delta = +10deg and
alpha = 321deg, delta = -23deg (beta < 20degS).
This is a fine, rich stream associated with Comet 1P/Halley, like the
Orionids of October, but it is visible for only a few hours before dawn
essentially from tropical and southern hemisphere sites. Some useful
results have come even from sites around 40deg 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 very low, eta-Aquarid meteors tend to have very long paths
too, which can mean observers underestimate the apparent speeds of the
meteors, so extra care is needed when making such angular speed estimates.
A relatively broad maximum, sometimes with a variable number of submaxima,
usually occurs in early May. ZHRs are generally above 30 for almost a week
centred on the main peak, based on IMO observations between 1988-1997. With
new Moon on May 4, the shower is perfectly-placed for watchers in 2000. All
forms of observing can be used to study the eta-Aquarids, with radio work
allowing activity to be followed even from mid-northern latitude sites
throughout the daylight morning hours. The radiant culminates at about 08h
local time.
June Bootids
------------
Active: June 26-Jul 02; Maximum: June 27, 01h UT (lambda = 95.7deg);
ZHR = variable, 0--100+;
Radiant: alpha = 224deg, delta = +48deg; Radiant drift: see Table 6;
V = 18 km/s; r = 2.2;
TFC: alpha = 156deg, delta = +64deg and
alpha = 289deg, delta = +67deg (beta = 25deg-60deg N).
Following the wholly unexpected strong return of this shower in 1998, we
are delighted to reintroduce the June Bootids to the Working List of visual
meteor showers this year, and to encourage all observers to routinely
monitor the expected activity period in case of future outbursts. Prior to
1998, only four definite returns of the shower had been detected, in 1916,
1921 and 1927. With no significant visual reports between 1928-1997, we
were justified in assuming the stream no longer encountered the Earth, and
accordingly removed the shower from the Working List in 1996. The dynamics
of the stream are not well understood. The shower's parent comet 7P/Pons-
Winnecke was last at perihelion in January 1996, and its orbit currently
lies around 0.24 astronomical units outside the Earth's orbit at its
closest approach, so we have no way at present to predict likely future
activity. In 1998, high Bootid rates (ZHRs 50-100+) were visible for more
than half a day, beginning shortly before the time indicated above, again
quite contrary to the short-lived nature of other known shower outbursts.
The radiant is at a useful elevation for most of the short summer night in
the northern hemisphere (only), and the waning crescent Moon, just four
days from new, will present no real problems.
July to September
-----------------
Minor shower activity continues apace from near-ecliptic sources throughout
this quarter, first from the Sagittarids, then the Aquarid and Capricornid
showers, and finally the Piscids (whose most likely peak on September 19
will suffer from the bright waning Moon) into September. The two strongest
sources, the Southern delta-Aquarids and the alpha-Capricornids, are free
from moonlight this year, along with the less-active Piscis Austrinids,
Southern iota-Aquarids and Northern delta-Aquarids. Something of the
Pegasids should still be seen in early July as well, but the July
Phoenicids (peak July 13), Perseids (maxima expected near 05h and 10h UT on
August 12; if the tertiary peak - seen so far only in 1997 - repeats in
2000, that should fall around 19h UT on August 12), kappa-Cygnids (maximum
August 17) and Northern iota-Aquarids (peak August 19) all lose their best
rates to bright moonlight. The alpha-Aurigids are much more favourable, and
even the delta-Aurigids in early September are not too unfavourable. For
daylight radio observers, the interest of May-June has waned, but there
remain the visually-inaccessible gamma-Leonids (peak circa August 25, 03h
UT, though not found in recent radio results), and a tricky visual shower,
the Sextantids (maximum expected September 27, 03h UT, but possibly
occurring a day earlier). The latter prediction is perfectly timed for new
Moon, though the radiant rises less than an hour before dawn in either
hemisphere.
Pegasids
--------
Active: July 7-13; Maximum: July 9 (lambda = 107.5deg);
ZHR = 3;
Radiant: alpha = 340deg, delta = +15deg, Radiant drift: see Table 6;
V = 70km/s; r = 3.0;
TFC: alpha = 320deg, delta = +10deg and
alpha = 332deg, delta = +33deg (beta > 40deg N);
alpha = 357deg, delta = +02deg (beta < 40deg N).
Monitoring this short-lived minor shower is never easy, as a few cloudy
nights mean its loss for visual observers. The shower is best-seen in the
second half of the night, good news as the waxing gibbous Moon will set
soon after midnight for the more favorable northern hemisphere sites, to
00h30m at 35deg S latitude. The maximum ZHR is generally low, and swift,
faint meteors can be expected. Telescopic observing would be especially
useful.
Piscis Austrinids and Aquarid/Capricornid Complex
-------------------------------------------------
Piscis Austrinids
-----------------
Active: July 15-August 10; Maximum: July 27 (lambda = 125deg);
ZHR = 5;
Radiant: alpha = 341deg, delta = -30deg, Radiant drift: see Table 6;
V = 35 km/s; r = 3.2;
TFC: alpha= 255deg - 000deg, delta = 00deg - +15deg,
choose pairs separated by about 30deg in alpha (beta < 30deg N).
Southern delta-Aquarids
-----------------------
Active: July 12-August 19; Maximum: July 27, 18h UT (lambda = 125deg);
ZHR = 20;
Radiant: alpha = 339deg, delta = -16deg, Radiant drift: see Table 6;
V = 41 km/s; r = 3.2;
TFC: alpha= 255deg - 000deg, delta = 00deg - +15deg,
choose pairs separated by about 30deg in alpha (beta < 40deg N).
alpha-Capricornids
------------------
Active: July 3-August 15; Maximum: July 29 (lambda = 127deg);
ZHR = 4;
Radiant: alpha = 307deg, delta = -10deg, Radiant drift: see Table 6;
V = 23 km/s; r = 2.5;
TFC: alpha = 255deg - 000deg, delta = 00deg - +15deg,
choose pairs separated by about 30deg in alpha (beta < 40deg N);
PFC: alpha = 300deg, delta = +10deg (beta > 40deg N),
alpha = 320deg, delta = -05deg (beta = 0deg - 45deg N),
alpha = 300deg, delta = -25deg (beta < 0deg).
Southern iota-Aquarids
----------------------
Active: July 25-August 15; Maximum: August 4 (lambda = 132deg);
ZHR = 2;
Radiant: alpha = 334deg, delta = -15deg, Radiant drift: see Table 6;
V = 34 km/s; r = 2.9;
TFC: alpha = 255deg - 000deg, delta = 00deg - +15deg,
choose pairs separated by about 30deg in alpha (beta < 30deg N).
Northern delta-Aquarids
-----------------------
Active: July 15-August 25; Maximum: August 8 (lambda = 136deg);
ZHR = 4;
Radiant: alpha = 335deg, delta = -05deg, Radiant drift: see Table 6;
V = 42 km/s; r = 3.4;
TFC: alpha = 255deg - 000deg, delta = 00deg - +15deg,
choose pairs separated by about 30deg in alpha (beta < 30deg N).
The Aquarids and Piscis Austrinids are all streams rich in faint meteors,
making them well-suited to telescopic work, although enough brighter
members exist to make visual and photographic observations worth the effort
too, primarily from more southerly sites. Radio work can be used to pick up
the Southern delta-Aquarids especially, as the most active of these
showers. The alpha-Capricornids are noted for their bright - sometimes
fireball-class - events, 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 alpha-Capricornid ZHRs to
around 10 was noted in 1995 by European IMO observers, although the
Southern delta-Aquarids were the only one of these streams previously
suspected of occasional variability.
Such a concentration of radiants in a small area of sky means that
familiarity with where all the radiants are is essential for accurate
shower association for all observing nights. Visual watchers in particular
should plot all potential stream members seen in this region of sky rather
than trying to make shower associations in the field. The only exception is
when the Southern delta-Aquarids are near their peak, as from southern
hemisphere sites in particular, rates may become too high for accurate
plotting.
In 2000 the Piscis Austrinid, Southern delta-Aquarid, alpha-Capricornid and
Northern iota-Aquarid maxima benefit from new Moon on July 31, while the
Northern delta-Aquarid peak has only a few problems from the waxing gibbous
Moon, which will set between 23h and 01h30m local time in either
hemisphere. All these radiants are above the horizon for much of the night.
alpha- and delta-Aurigids
-------------------------
alpha-Aurigids
--------------
Active: August 25-September 5; Maximum: August 31, 18h UT (lambda = 158.6deg);
ZHR = 10;
Radiant: alpha = 084deg, delta = +42deg, Radiant drift: see Table 6;
V = 66 km/s; r = 2.5;
TFC: alpha = 052deg, delta = +60deg;
alpha = 043deg, delta = +39deg and
alpha = 023deg, delta = +41deg (beta > 10deg S).
delta-Aurigids
--------------
Active: September 5-October 10; Maximum: September 8 (lambda = 166deg);
ZHR = 6;
Radiant: alpha = 060deg, delta = +47deg, Radiant drift: see Table 6;
V = 64 km/s; r = 3.0;
TFC: alpha = 052deg, delta = +60deg;
alpha = 043deg, delta = +39deg and
alpha = 023deg, delta = +41deg (beta > 10deg S).
These are both essentially northern hemisphere showers, badly in need of
more observations. They are part of a series of poorly-observed showers
with radiants in Aries, Perseus, Cassiopeia and Auriga, active from late
August into October. British and Italian observers independently reported a
possible new radiant in Aries during late August 1997 for example. Of the
known showers, the alpha-Aurigids are the more active, with short
unexpected bursts having given EZHRs of around 30-40 in 1935, 1986 and
1994, although they have not been monitored regularly until very recently,
so other outbursts may have been missed. The delta-Aurigids typically
produce low rates of generally faint meteors, and have yet to be well-seen
in more than an occasional year. Both radiants reach a useful elevation
only after 23h-00h local time, meaning lunar circumstances are near perfect
for the alpha-Aurigid peak in 2000, with new Moon on August 29, while the
delta-Aurigids enjoy dark skies after moonset (between 00h-01h local time
north of 20deg N latitude). Telescopic data to examine all the radiants in
this region of sky - and possibly observe the telescopic beta-Cassiopeids
simultaneously - would be especially valuable, but photographs, video
records and visual plotting would be welcomed too.
October to December
-------------------
Ecliptical minor shower activity reaches what might be regarded as a peak
in early to mid November, with the Taurid streams in action. Unfortunately,
both Northern and Southern Taurid maxima suffer from bright moonlight this
year, but the interesting late October to early November period which
sometimes produces more Taurid fireballs is excellently Moon-free. Taurid
activity in late October 1998 reached levels comparable to the usual
maximum rates, and checking what happens this year would be valuable,
though nothing unusual has been predicted. Before then is a partly moonless
Draconid epoch, together with badly Moon- affected epsilon-Geminid and
Orionid maxima, all in October. The main Orionid peak is likely around
02h-03h UT on October 21 for radio observers. Some predictions suggest a
Leonid storm may occur in November, but moonlight will be a problem.
However, the alpha-Monocerotid peak is nearly Moon-free, together with the
chi-Orionids in December. Shower maxima lost to moonlight in December
include those of the Phoenicids (December 6 around 02h UT), early
December's best from the Puppid-Velids, the Monocerotids (December 8),
sigma-Hydrids (December 11), Geminids (December 13, 17h UT to December 14,
02h UT) and Coma Berenicids (December 19). The Ursids at least survive this
lunar-light onslaught.
Draconids
---------
Active: October 6-10; Maximum: October 8, 01h30m UT (lambda = 195.075deg) or
around October 8, 09h UT (lambda = 195.4deg);
ZHR = periodic, up to storm levels;
Radiant: alpha = 262deg, delta = +54deg, Radiant drift: negligible;
V = 20 km/s; r = 2.6;
TFC: alpha = 290deg, delta = +65deg and
alpha = 288deg, delta = +39deg (beta > 30deg N).
Unfortunately for potential Draconid observers, although this periodic
shower has produced spectacular, brief, meteor storms twice already this
century, in 1933 and 1946, and lower rates in several other years (ZHRs
around 20-500+), so far, detectable activity has only been seen in years
when the stream's parent comet, 21P/Giacobini-Zinner, has returned to
perihelion. It did this last in 1998 November, and in 1998 October, a
short-lived Draconid outburst yielding ZHRs of around 700 was seen from Far
Eastern sites, as well as being recorded by radio. This occurred at lambda
= 195.075deg, but a later time towards lambda = 195.4deg may be more
generally applicable, based on the Earth's closest approach to the comet
orbit's node. Activity in 2000 is unlikely, and conditions are far from
ideal with a waxing gibbous Moon, but checking is important. The radiant is
circumpolar from many northern hemisphere locations, but is higher in the
pre-midnight and near-dawn hours on October 8-10. With moonset only after
local midnight, a repeat of the 1998 peak time would favour sites in
central to eastern North America, while the later time would be better for
European to West Asian observers. Note that Draconid meteors are
exceptionally slow-moving, a characteristic which helps separate genuine
shower meteors from sporadics accidentally lining up with the radiant.
Leonids
-------
Active: November 14-21; Maximum: November 17, 08h UT (lambda = 235.27deg);
ZHR = 100+ (around 150? in 1997, around 340 in 1998),
but may reach storm level in 2000;
Radiant: alpha = 153deg, delta = +22deg, Radiant drift: see Table 6;
V = 71 km/s; r = 2.9;
TFC: alpha = 140deg, delta = +35deg and
alpha = 129deg, delta = +06deg (beta > 35deg N); or
alpha = 156deg, delta = -03deg and
alpha = 129deg, delta = +06deg (beta < 35deg N).
PFC: alpha = 120deg, delta = +40deg before 00h local time (beta > 40deg N);
alpha = 120deg, delta = +20deg before 04h local time and
alpha = 160deg, delta = 00deg after 04h local time (beta > 00deg~N);
alpha = 120deg, delta = +10deg before 00h local time and
alpha = 160deg, delta = -10deg (beta < 0deg N).
The Leonids' parent comet, 55P/Tempel-Tuttle, reached perihelion last in
1998 February, but recent stream evolution studies suggest high to storm-
level Leonid activity may still occur in 2000 or even until 2002. There
are, of course, no guarantees that this will happen, but all observers must
realise that even discovering the absence of any unusual Leonid activity
would still be very valuable information --- albeit not all that
interesting to witness! Young material from the most recent, i.e. the 1965
and 1932 perihelion passages of the comet, is likely to cause enhanced
activity near closest approach to the comet's node on November 17, 08h UT
(lambda = 235.27deg), as also indicated by the stream model developed by
Peter Brown, but the model finds an older trail from 1733 suggesting a peak
as late as November 18, 08h UT. This finding is supported by the studies of
David Asher and Robert McNaught yielding November 18, 03h45m for the 1733
trail and another possible peak at 07h50m for the 1866 trail. A repeat of
the spectacular and extended fireball outburst seen in 1998 is regrettably
unlikely this year.
The radiant rises only around local midnight (or indeed afterwards south of
the equator), so the waning gibbous Moon will be a considerable nuisance
for all observers. The two around 08h UT peak timings would favor locations
across North America, while the 03h45m possible peak would be best-seen
from Europe and North Africa. Even minor variations from these timings
would mean places east or west of these zones may see something of the
shower's best too. Look out for further updates in the IMO's journal WGN
after the 1999 return. All observing methods should be utilised, especially
photography and video if a storm manifests.
alpha-Monocerotids
------------------
Active: November 15-25; Maximum: November 21, 08h UT (lambda = 239.32deg);
ZHR = variable, usually 5, but may produce outbursts to 400+;
Radiant: alpha = 117deg, delta = +01deg, Radiant drift: see Table 6;
V = 65 km/s; r = 2.4;
TFC: alpha = 115deg, delta = +23deg and
alpha = 129deg, delta = +20deg (beta > 20deg N); or
alpha = 110deg, delta = -27deg and
alpha = 098deg, delta = +06deg (beta < 20deg N).
Another late-year shower capable of producing surprises, the alpha-
Monocerotids gave their most recent brief outburst in 1995 (the top EZHR,
around 420, lasted just five minutes; the entire outburst 30 minutes). Many
observers across Europe witnessed it, and we have been able to completely
update the known shower parameters as a result. Whether this indicates the
proposed ten-year periodicity in such returns is real or not, only the
future will tell, however, so all observers should continue to monitor this
source closely. We are currently at the mid-point of any decade-long cycle.
The waning crescent Moon on November 21 makes this a good year for such
scrutiny, with the radiant well on view in both hemispheres after about 23h
local time or so. The expected peak time falls especially well for North
America.
chi-Orionids
------------
Active: November 26-December 15; Maximum: December 1 (lambda = 250deg);
ZHR = 3;
Radiant: alpha = 082deg, delta= +23deg,
Radiant drift: see Table 6;
V = 28 km/s; r = 3.0;
TFC: alpha = 083deg, delta= +09deg and
alpha = 080deg, delta= +24deg (beta > 30deg S).
A weak visual stream, but moderately active telescopically. Some brighter
meteors have been photographed too. The shower has at least a double
radiant, but the southern branch has been rarely detected. The chi-Orionids
may be a continuation of the ecliptic complex after the Taurids cease to be
active. The radiant used here is a combined one, suitable for visual work,
although telescopic or video observations should be better-able to
determine the exact radiant structure. The waxing crescent Moon should give
few problems, as the radiant is well on display in both hemispheres
throughout the night.
Ursids
-------
Active: December 17-26; Maximum: December 22, 06h UT (lambda = 270.7deg);
ZHR = 10 (occasionally variable up to 50);
Radiant: alpha = 217deg, delta = +76deg, Radiant drift: see Table 6;
V = 33 km/s; r = 3.0;
TFC: alpha = 348deg, delta = +75deg and
alpha = 131deg, delta = +66deg (beta > 40deg N);
alpha = 063deg, delta = +84deg and
alpha = 156deg, delta = +64deg (beta = 30deg - 40deg N).
A very poorly-observed northern hemisphere shower, but one which has
produced at least two major outbursts in the past half-century or so, in
1945 and 1986. Several other rate enhancements, recently in 1988 and 1994,
have been reported too. Other similar events could easily have been missed
due to poor weather or too few observers active. All forms of observation
can be used for the shower, since many of its meteors are faint, but with
so little work carried out on the stream, it is impossible to be precise in
making statements about it. The radio maximum in 1996 occurred around
lambda = 270.8deg, for instance, which might suggest a slightly later
maximum time in 1998 of December 22, 08h30m UT. The Ursid radiant is
circumpolar from most northern sites (thus fails to rise for most southern
ones), though it culminates after daybreak, and is highest in the sky later
in the night. The nearly-new Moon will give dark skies for observations
almost all night on December 22.
Radiant sizes and meteor plotting
---------------------------------
If you are not observing during a major-shower maximum, it is much more
essential to associate meteors with their radiants correctly, since the
total numbers will be small. Meteor plotting allows the a shower
association by more objective criteria than the prolongation of paths under
the sky. As you plotted the meteors on gnomonic maps, you can trace the
radiant by straight lines. If the radiant lies on another chart, you should
find common stars on an adjacent chart to extend the backward prolongation
there.
How large should the radiant be assumed for shower association? The
physical radiant size is very small; visual plotting errors cause many true
shower meteors to pass the radiant outside this area. We have to asume a
larger radiant. The opposite behavior is caused by sporadic meteors - more
and more sporadics line up accidentally upon enlarging the radiant. Hence,
we have to apply an optimum radiant diameter compensating the loss due to
plotting errors, and the sporadic meteor pollution. Table 1 gives the
optimum diameter as a function of the distance of the meteor from the
radiant.
--------------------------
Table 1
Optimum radiant diameters to be assumed for shower association of minor-
shower meteors as a function of the radiant distance D of the meteor.
--------------------------
D optimum diameter
--------------------------
15deg 14deg
30deg 17deg
50deg 20deg
70deg 23deg
--------------------------
The direction of the path is not the only criterion for shower association.
The angular velocity of the meteor should match the expected speed of the
shower meteors according to the geocentric velocity of the meteoroids.
Angular velocity estimates should be made in degrees per second (deg/s). In
your imagination you make the meteors move for one second. The path length
of this imaginary meteor is the angular velocity in deg/s. Note that
typical speeds are in the range 3deg/s to 25deg/s. Typical errors of such
estimates are given in Table 2.
-------------------------------------------
Table 2
Error limits for the angular velocity
-------------------------------------------
angular velocity [deg/s] 5 10 15 20 30
permitted error [deg/s] 3 5 6 7 8
-------------------------------------------
If you found a meteor which hits the radiant within the above diameter,
check its angular velocity. Table 3 gives the angular speeds for a few
geocentric velocities, which can be looked up in Table 5 for each shower.
------------------------------------
Table 3
Angular velocities as a function of the radiant distance of the meteor and
the elevation of the meteor for three different geocentric velocities. All
velocities are in deg/s. (The tables are symmetric in D and h.)
v=25 km/s
D 10deg 20deg 40deg 60deg 90deg
h
10deg 0.4 0.9 1.6 2.2 2.5
20deg 0.9 1.7 3.2 4.3 4.9
40deg 1.6 3.2 5.9 8.0 9.3
60deg 2.2 4.3 8.0 11 13
90deg 2.5 4.9 9.3 13 14
v=40 km/s
D 10deg 20deg 40deg 60deg 90deg
h
10deg 0.7 1.4 2.6 3.5 4.0
20deg 1.4 2.7 5.0 6.8 7.9
40deg 2.6 5.0 9.5 13 15
60deg 3.5 6.8 13 17 20
90deg 4.0 7.9 15 20 23
v=60 km/s
D 10deg 20deg 40deg 60deg 90deg
h
10deg 0.9 1.8 3.7 4.6 5.3
20deg 1.8 3.5 6.7 9.0 10
40deg 3.7 6.7 13 17 20
60deg 4.6 9.0 17 23 26
90deg 5.3 10 20 26 30
------------------------------------
Abbreviations
-------------
drift across the sky each day due to the Earth's own orbital motion around
alpha, delta: Coordinates for a shower's radiant position, usually at the Sun, and this must be allowed for using the details in Table 6 for nights away from the listed shower maxima.
maximum. alpha is right ascension, delta is declination. Radiants
r: The population index, a term computed from each shower's meteor
magnitude distribution. r = 2.0 - 2.5 is brighter than average, while r
above 3.0 is fainter than average.
lambda: Solar longitude, a precise measure of the Earth's position
on its orbit which is not dependent on the vagaries of the calendar. All
lambda are given for the equinox 2000.0.
V: Atmospheric or apparent meteoric velocity given in km/s. Velocities
range from about 11 km/s (very slow) to 72 km/s (very fast). 40 km/s is
roughly medium speed.
ZHR: Zenithal Hourly Rate, a calculated maximum number of meteors an
ideal observer would see in perfectly clear skies with the shower
radiant overhead. This figure is given in terms of meteors per hour.
Where meteor activity persisted at a high level for less than an hour,
or where observing circumstances were very poor, an estimated ZHR (EZHR)
is used, which is less accurate than the normal ZHR.
TFC and PFC: Suggested telescopic and small-camera photographic field
centers respectively. beta is the observer's latitude ("<" means "south
of" and ">" means "north of"). Pairs of telescopic fields must be
observed, alternating about every half hour, so that the positions of
radiants can be defined. The exact choice of TFC or PFC depends on the
observer's location and the elevation of the radiant. Note that the TFCs
are also useful centers to use for video camera fields as well.
---------------------------------------------------------------
Table 4
Lunar phases for 2000.
New Moon First Quarter Full Moon Last Quarter
January 6 January 14 January 21 January 28
February 5 February 12 February 19 February 27
March 6 March 13 March 20 March 28
April 4 April 11 April 18 April 26
May 4 May 10 May 18 May 26
June 2 June 9 June 16 June 25
July 1 July 8 July 16 July 24
July 31 August 7 August 15 August 22
August 29 September 5 September 13 September 21
September 27 October 5 October 13 October 20
October 27 November 4 November 11 November 18
November 25 December 4 December 11 December 18
December 25
---------------------------------------------------------------
---------------------------------------------------------------------------
Table 5
Working list of visual meteor showers. Details in this Table were correct
according to the best information available in June 1999. Contact the IMO's
Visual Commission for more information. Maximum dates in parentheses
indicate reference dates for the radiant, not true maxima. Some showers
have ZHRs that vary from year to year. The most recent reliable figure is
given here, except for possibly periodic showers that are noted as ``var.''
= variable.
Activity Maximum Radiant
Shower Period Date lambda alpha delta
[deg] [deg] [deg]
Quadrantids Jan 01-Jan 05 Jan 04 283.16 230 +49
delta-Cancrids Jan 01-Jan 24 Jan 17 297 130 +20
alpha-Centaurids Jan 28-Feb 21 Feb 08 319.2 210 -59
delta-Leonids Feb 15-Mar 10 Feb 25 336 168 +16
gamma-Normids Feb 25-Mar 22 Mar 13 353 249 -51
Virginids Jan 25-Apr 15 (Mar 24)(004) 195 -04
Lyrids Apr 16-Apr 25 Apr 21 032.1 271 +34
pi-Puppids Apr 15-Apr 28 Apr 23 033.5 110 -45
eta-Aquarids Apr 19-May 28 May 05 045.5 338 -01
Sagittarids Apr 15-Jul 15 (May 19)(059) 247 -22
June Bootids Jun 26-Jul 02 Jun 27 095.7 224 +48
Pegasids Jul 07-Jul 13 Jul 09 107.5 340 +15
July Phoenicids Jul 10-Jul 16 Jul 13 111 032 -48
Pisces Austrinids Jul 15-Aug 10 Jul 27 125 341 -30
Southern delta-Aquarids Jul 12-Aug 19 Jul 27 125 339 -16
alpha-Capricornids Jul 03-Aug 15 Jul 29 127 307 -10
Southern iota-Aquarids Jul 25-Aug 15 Aug 04 132 334 -15
Northern delta-Aquarids Jul 15-Aug 25 Aug 08 136 335 -05
Perseids Jul 17-Aug 24 Aug 12 *139.8 046 +58
kappa-Cygnids Aug 03-Aug 25 Aug 17 145 286 +59
Northern iota-Aquarids Aug 11-Aug 31 Aug 19 147 327 -06
alpha-Aurigids Aug 25-Sep 05 Aug 31 158.6 084 +42
delta-Aurigids Sep 05-Oct 10 Sep 08 166 060 +47
Piscids Sep 01-Sep 30 Sep 19 177 005 -01
Draconids Oct 06-Oct 10 Oct 08 *195.4 262 +54
epsilon-Geminids Oct 14-Oct 27 Oct 18 205 102 +27
Orionids Oct 02-Nov 07 Oct 21 208 095 +16
Southern Taurids Oct 01-Nov 25 Nov 05 223 052 +13
Northern Taurids Oct 01-Nov 25 Nov 12 230 058 +22
Leonids Nov 14-Nov 21 Nov 17 *235.27 153 +22
alpha-Monocerotids Nov 15-Nov 25 Nov 21 239.32 117 +01
chi-Orionids Nov 26-Dec 15 Dec 01 250 082 +23
Phoenicids Nov 28-Dec 09 Dec 06 254.25 018 -53
Puppid-Velids Dec 01-Dec 15 (Dec 06)(255) 123 -45
Monocerotids (Dec) Nov 27-Dec 17 Dec 08 257 100 +08
sigma-Hydrids Dec 03-Dec 15 Dec 11 260 127 +02
Geminids Dec 07-Dec 17 Dec 13 *262.0 112 +33
Coma Berenicids Dec 12-Jan 23 Dec 19 268 175 +25
Ursids Dec 17-Dec 26 Dec 22 270.7 217 +76
IMO
Shower v r ZHR Code
[km/s]
Quadrantids 41 2.1 120 QUA
delta-Cancrids 28 3.0 4 DCA
alpha-Centaurids 56 2.0 6 ACE
delta-Leonids 23 3.0 2 DLE
gamma-Normids 56 2.4 8 GNO
Virginids 30 3.0 5 VIR
Lyrids 49 2.9 15 LYR
pi-Puppids 18 2.0 var. PPU
eta-Aquarids 66 2.7 60 ETA
Sagittarids 30 2.5 5 SAG
June Bootids 18 2.2 var. JBO
Pegasids 70 3.0 3 JPE
July Phoenicids 47 3.0 var. PHE
Pisces Austrinids 35 3.2 5 PAU
Southern delta-Aquarids 41 3.2 20 SDA
alpha-Capricornids 25 2.5 4 CAP
Southern iota-Aquarids 34 2.9 2 SIA
Northern delta-Aquarids 42 3.4 4 NDA
Perseids 59 2.6 140 PER
kappa-Cygnids 25 3.0 3 KCG
Northern iota-Aquarids 31 3.2 3 NIA
alpha-Aurigids 66 2.5 10 AUR
delta-Aurigids 64 3.0 6 DAU
Piscids 26 3.0 3 SPI
Draconids 20 2.6 var. GIA
epsilon-Geminids 70 3.0 2 EGE
Orionids 66 2.9 20 ORI
Southern Taurids 27 2.3 5 STA
Northern Taurids 29 2.3 5 NTA
Leonids 71 2.5 100+ LEO
alpha-Monocerotids 65 2.4 var. AMO
chi-Orionids 28 3.0 3 XOR
Phoenicids 18 2.8 var. PHO
Puppid-Velids 40 2.9 10 PUP
Monocerotids (Dec) 42 3.0 3 MON
sigma-Hydrids 58 3.0 2 HYD
Geminids 35 2.6 120 GEM
Coma Berenicids 65 3.0 5 COM
Ursids 33 3.0 10 URS
* Showers may have other or additional peak times; see text.
---------------------------------------------------------------------------
---------------------------------------------------------------------------
Table 6: Radiant positions during the year in alpha and delta.
COM DCA QUA
Jan 0 186 +20 112 +22 228 +50
Jan 5 190 +18 116 +22 231 +49
Jan 10 194 +17 121 +21
Jan 20 202 +13 130 +19 ACE VIR
Jan 30 200 -57 157 +16 DLE
Feb 10 214 -60 165 +10 155 +20 GNO
Feb 20 225 -63 172 +6 164 +18 225 -53
Feb 28 178 +3 171 +15 234 -52
Mar 10 186 0 180 +12 245 -51
Mar 20 192 -3 256 -50
Mar 30 198 -5
Apr 10 SAG LYR PPU 203 -7
Apr 15 224 -17 263 +34 106 -44 ETA 205 -8
Apr 20 227 -18 269 +34 109 -45 323 -7
Apr 25 230 -19 274 +34 111 -45 328 -5
Apr 30 233 -19 332 -4
May 5 236 -20 337 -2
May 10 240 -21 341 0
May 20 247 -22 350 +5
May 30 256 -23
Jun 10 265 -23
Jun 15 270 -23
Jun 20 275 -23 JBO
Jun 25 280 -23 223 +48
Jun 30 284 -23 225 +47 CAP JPE
Jul 5 289 -22 285 -16 SDA 338 +14
Jul 10 293 -22 PHE 289 -15 325 -19 NDA 341 +15 PER PAU
Jul 15 298 -21 032 -48 294 -14 329 -19 316 -10 012 +51 330 -34
Jul 20 299 -12 333 -18 319 -9 SIA 018 +52 334 -33
Jul 25 303 -11 337 -17 323 -9 322 -17 023 +54 338 -31
Jul 30 KCG 308 -10 340 -16 327 -8 328 -16 029 +55 343 -29
Aug 5 283 +58 NIA 313 -8 345 -14 332 -6 334 -15 037 +57 348 -27
Aug 10 284 +58 317 -7 318 -6 349 -13 335 -5 339 -14 043 +58 352 -26
Aug 15 285 +59 322 -7 352 -12 339 -4 345 -13 050 +59
Aug 20 286 +59 327 -6 AUR 356 -11 343 -3 057 +59
Aug 25 288 +60 332 -5 076 +42 347 -2 065 +60
Aug 30 289 +60 337 -5 082 +42 DAU
Sep 5 088 +42 055 +46 SPI
Sep 10 060 +47 357 -5
Sep 15 066 +48 001 -3
Sep 20 071 +48 005 -1
Sep 25 NTA STA 077 +49 009 0
Sep 30 021 +11 023 +5 ORI 083 +49 013 +2
Oct 5 025 +12 027 +7 085 +14 089 +49 GIA
Oct 10 029 +14 031 +8 088 +15 095 +49 262 +54
Oct 15 034 +16 035 +9 091 +15 EGE
Oct 20 038 +17 039 +11 094 +16 099 +27
Oct 25 043 +18 043 +12 098 +16 104 +27
Oct 30 047 +20 047 +13 101 +16 109 +27
Nov 5 053 +21 052 +14 105 +17
Nov 10 058 +22 056 +15 LEO AMO
Nov 15 062 +23 060 +16 150 +23 113 -5
Nov 20 067 +24 064 +16 XOR 153 +21 117 -6
Nov 25 072 +24 069 +17 075 +23 121 -7 MON PUP PHO
Nov 30 080 +23 HYD 091 +8 120 -45 014 -52
Dec 5 COM GEM 085 +23 122 +3 096 +8 122 -45 018 -53
Dec 10 169 +27 108 +33 090 +23 126 +2 100 +8 125 -45 022 -53
Dec 15 173 +26 113 +33 094 +23 130 +1 URS 104 +8 128 -45
Dec 20 177 +24 118 +32 217 +75
---------------------------------------------------------------------------
---------------------------------------------------------------------------
Table 7: Working list of daytime radio meteor streams. The "Best Observed"
columns give the approximate local mean times between which a four-element
antenna at an elevation of 45deg receiving a signal from a 30-kW
transmitter 1000 km away should record at least 85% of any suitably
positioned radio-reflecting meteor trails for the appropriate latitudes.
Note that this is often heavily dependent on the compass direction in which
the antenna is pointing, however, and applies only to dates near the
shower's maximum.
Shower Activity Max lambda Radiant Best Observed Rate
Date 2000.0 alpdot del. 50 N 35 S
Cap/Sagittarids Jan 13-Feb 04 Feb 02 312.5 299 -15 11h-14h 09h-14h medium
chi-Capricornids Jan 29-Feb 28 Feb 14 324.7 315 -24 10h-13h 08h-15h low
Piscids (Apr.) Apr 08-Apr 29 Apr 20 030.3 007 +7 07h-14h 08h-13h low
delta-Piscids Apr 24-Apr 24 Apr 24 034.2 011 +12 07h-14h 08h-13h low
epsilon-Arietids Apr 24-May 27 May 08 048.7 044 +21 08h-15h 10h-14h low
Arietids (May) May 04-Jun 06 May 16 055.5 037 +18 08h-15h 09h-13h low
o-Cetids May 05-Jun 02 May 19 059.3 028 -4 07h-13h 07h-13h medium
Arietids May 22-Jul 02 Jun 07 076.7 044 +24 06h-14h 08h-12h high
zeta-Perseids May 20-Jul 05 Jun 09 078.6 062 +23 07h-15h 09h-13h high
beta-Taurids Jun 05-Jul 17 Jun 28 096.7 086 +19 08h-15h 09h-13h medium
gamma-Leonids Aug 14-Sep 12 Aug 25 152.2 155 +20 08h-16h 10h-14h low
Sextantids Sep 09-Oct 09 Sep 27 184.3 152 0 06h-12h 06h-13h medium
---------------------------------------------------------------------------
Useful addresses
For more information on observing techniques, and when submitting results,
please contact the appropriate IMO Commission Director:
Fireball Data Center (FIDAC): A. Knoeofel, Saarbruecker Strasse 8,
D-40476 Duesseldorf, Germany. e-mail: fidac@imodot net
Photographic Commission: M. de Lignie, Prins Hendrikplein 42, NL-2264 SN
Leidschendam, The Netherlands. e-mail: photo@imodot net
Radio Commission: Temporarily vacant. e-mail: radio@imodot net
Telescopic Commission: M. Currie, 660 N'Aohoku Place, Hilo, HI 96720,
USA. e-mail: tele@imodot net
Video Commission: S. Molau, Weidenweg 1, D-52074 Aachen, Germany.
e-mail: video@imodot net
Visual Commission: R. Arlt, Friedenstrasse 5, D-14109 Berlin, Germany.
email: visual@imodot net
or contact IMO's Homepage on the World-Wide-Web: http://www.imodot net/
For further details on IMO membership, please write to: Ina Rendtel, IMO
Treasurer, Mehlbeerenweg 5, D-14469 Potsdam, Germany. e-mail:
treasurer@imodot net
Please try to enclose return postage when writing to any IMO
officials,
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