Potential Draconid hunting should be practical this year in early October.
Unfortunately, things are less helpful for the very weak ε-Geminids
(maximum due on October 18) and the major Orionids (main peak expected on
October 21), which are both lost to waning gibbous moonlight. As the Moon rolls
on, Taurid-watching from late October to almost mid-November is chiefly Moon-
free. Later, the Leonids must endure full Moon near their probable maximum,
towards 14h30m UT on November 17. Although the α-Monocerotid peak is also
badly moonlit, the shower is highlighted here on the tenth anniversary of its
latest outburst. The early December mostly minor shower maxima are acceptably
free from moonlight through to the sigma-Hydrids, but this means both the major
Geminids (maximum within 2 h 20 m of 4h30m UT on December 14) and the minor Coma
Berenicids (peak around December 19) are both swamped by full moonlight.
Something of the Ursids at least should still be seen without the Moon.
Draconids
Active : October 6-10; Maximum : October 8, 16h UT (sol = 195.195°, but see below); ZHR : periodic, up to storm levels; Radiant : alpha = 262°, delta = +54°; Radiant drift: negligible; V : 20 km/s r : 2.6; TFC : alpha = 290°, delta = +65° and alpha = 288°, delta = +39° (beta > 30° N).
[image:65]
Figure 11
– Radiant position of the Draconids.
The Draconids are primarily a periodic shower which produced spectacular,
brief, meteor storms twice last century, in 1933 and 1946, and lower rates in
several other years (ZHRs ~ 20-500+), most recently in 1998 (when EZHRs briefly
reached 700). Most detected showers were in years when the stream’s parent
comet, 21P/Giacobini-Zinner, returned to perihelion, as it did in 1998 November.
The comet returns to perihelion again in July this year, but whether it will
have any effect on the Draconids we see in 2005 is not clear. Earlier
theoretical discussions suggested an outburst was unlikely, but theory is not
always the perfect guide to reality! The 1998 outburst happened at sol =
195°075, equivalent to 2005 October 8, 8h15m UT, although the nodal
crossing time used above may be more generally applicable. In 1999 an unexpected
minor visual-radio outburst (ZHRs ~ 10-20) occurred over the Far East between
sol = 195°63-195°76. A repeat at this time would fall between 2005
October 8, 21h40m to October 9, 0h50m UT. The radiant is circumpolar from many
northern hemisphere locations, but is higher in the pre-midnight and near-dawn
hours of early October. The waxing crescent Moon sets by mid-evening on October
8 and 9 at such places, so much of the night will be available for dark-sky
observing, whatever the shower may yield – even if that is nothing detectable.
Draconid meteors are exceptionally slow-moving, a characteristic which helps
separate genuine shower meteors from sporadics accidentally lining up with the
radiant.
Taurids
Southern Taurids
Active : October 1-November 25; Maximum : November 5 (sol = 223°); ZHR : 5; Radiant : alpha = 052°, delta = +13°; Radiant drift: see Table 6; V : 27 km/s r : 2.3; TFC : Choose fields on the ecliptic and ~ 10° E or W of the radiants (beta > 40° S).
Northern Taurids
Active : October 1-November 25; Maximum : November 12 (sol = 230°); ZHR : 5; Radiant : alpha = 058°, delta = +22°; Radiant drift: see Table 6; V : 29 km/s r : 2.3; TFC : as Southern Taurids.
These two streams form part of the complex associated with Comet 2P/Encke.
Defining their radiants is best achieved by careful visual or telescopic
plotting, photography or video work, since they are large and diffuse. They are
currently being studied using IMO data by Mihaela Triglav. The brightness and
relative slowness of many shower meteors makes them ideal targets for
photography, while these factors coupled with low, steady, combined Taurid rates
makes them excellent targets for newcomers to practice their plotting techniques
on. The activity of both streams produces an apparently plateau-like maximum for
about ten days in early November, and the showers have a reputation for
producing some excellently bright fireballs at times, although seemingly not in
every year.
David Asher has indicated that increased Taurid fireball rates may result
from a “swarm” of larger particles within the Taurid stream complex, and he
suggested such “swarm” returns might happen in 1995 and 1998 most recently. In
1995, an impressive crop of bright Taurids occurred between late October to mid
November, while in 1998, Taurid ZHRs reached levels comparable to the usual
maximum rates in late October, together with an increased flux of brighter
Taurids generally. This year brings the next potential October-November “swarm”
return. Thus, observing what happens with the Taurids between last quarter Moon
in October through to the Northern Taurid maximum in November is most important,
especially as early November’s new Moon makes almost the whole of this spell
very favourable.
The near-ecliptic radiants for both shower branches mean all meteoricists
can observe the streams. Northern hemisphere observers are somewhat better-placed,
as here suitable radiant zenith distances persist for much of the late
autumnal nights. Even in the southern hemisphere, a good 3-5 hours’ watching
around local midnight is possible with Taurus well above the horizon,
however.
[image:67]
Figure 12
– Radiant position of the Northern and Southern Taurids.
α-Monocerotids
Active : November 15-25; Maximum : November 21, 15h00m UT (sol = 239.239°); ZHR : variable, usually ~ 5, but may produce outbursts to ~ 400+; Radiant : alpha = 117°, delta = +01°; Radiant drift: see Table 6; V : 65 km/s r : 2.4; TFC : alpha = 115°, delta = +23° and alpha = 129°, delta = +20° (beta > 20° N); or alpha = 110°, delta = -27° and alpha = 098°, delta = +06° (beta < 20° N).
Another late-year shower capable of producing surprises, the α-
Monocerotids gave their most recent brief outburst in 1995 (the top EZHR, ~ 420,
lasted just five minutes; the entire outburst 30 minutes). Many observers across
Europe witnessed it, and we were able to completely update the known shower
parameters as a result. Whether this indicates the proposed ten-year periodicity
- with heightened rates in 1925, 1935, 1985 and 1995 - is real or not, only this
year (or other future decadal returns) may tell, so all observers should
continue to monitor this source closely.
The waning gibbous Moon on November 21 is very bad news however, as it will
rise between mid to late evening across much of the world, ruining any chance of
dark skies for watchers, because the radiant is well on view from either
hemisphere only after about 23h local time. The expected peak time falls
especially well for sites around and in the western Pacific Ocean, including
eastern China, far eastern Russia, Japan, Oceania, and Alaska in North America.
With the Moon so problematic, visual observing will be extremely difficult, but
highly important, along with all other techniques, especially radio, which
should readily detect any strong outburst from this source.
χ-Orionids
Active : November 26-December 15; Maximum : December 2 (sol = 250°); ZHR : 3; Radiant : alpha = 082°, delta = +23°; Radiant drift: see Table 6; V : 28 km/s r : 3.0; TFC : alpha = 083°, delta = +09° and alpha = 080°, delta = +24° (beta > 30° S).
[image:72]
Figure 13
- Radiant position of the Geminids, χ-Orionids, Monocerotids, and sigma-Hydrids.
A weak visual stream, but one moderately active telescopically. Some
brighter meteors have been photographed from it too. The shower has at least a
double radiant, but the southern branch has been rarely detected. The χ-
Orionids may be a continuation of the ecliptic complex after the Taurids cease
to be active in late November.
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. It is well on display in both hemispheres throughout the
night, and new Moon on December 1 makes this a perfect year for watching it.
Phoenicids
Active : November 28-December 9; Maximum : December 6, 8h45m UT (sol = 254.254°); ZHR : variable, usually 3 or less, may reach 100; Radiant : alpha = 018°, delta = -53°; Radiant drift: see Table 6; V : 18 km/s r : 2.8; TFC : alpha = 040°, delta = -39° and alpha = 065°, delta = -62° (beta < 10° N).
Only one impressive Phoenicid return has so far been reported, that of its
discovery in 1956, when the EZHR was probably ~ 100, possibly with several peaks
spread over a few hours. Three other potential bursts of lower activity have
been reported, but never by more than one observer, under uncertain
circumstances. Reliable IMO data shows recent activity to be virtually
nonexistent. This may be a periodic shower however, and more observations of it
are needed by all methods. Lunar circumstances for southern hemisphere watchers
are quite good, with a waxing crescent Moon setting half an hour either side of
local midnight in most mid-southern locations on December 6, while the radiant
culminates at dusk, remaining well on view for most of the night.
Puppid-Velids
Active : December 1-15; Maximum : December ~ 7 (sol ~ 255°); ZHR ~ 10; Radiant : alpha = 123°, delta = -45°; Radiant drift: see Table 6; V : 40 km/s r : 2.9; TFC : alpha = 090° to 150g, delta = -20° to -60°; choose pairs of fields separated by about 30° in α, moving eastwards as the shower progresses (beta < 10° N).
This is a very complex system of poorly studied showers, visible chiefly to
those south of the equator. Up to ten sub-streams have been identified, with
radiants so tightly clustered, visual observing cannot readily separate them.
Photographic, video or telescopic work would thus be sensible, or very careful
visual plotting.
The activity is so badly known, we can only be reasonably sure that the
highest rates occur in early to mid December, coincident with a waxing Moon this
year. Some of these showers may be visible from late October to late January.
Most Puppid-Velid meteors are quite faint, but occasional bright fireballs,
notably around the suggested maximum here, have been reported previously. The
radiant area is on-view all night, but is highest towards dawn, so the better
radiant elevations will happen after moonset.
Monocerotids
Active : November 27-December 17; Maximum : December 9 (sol = 257°); ZHR : 3; Radiant : alpha = 100°, delta = +08°; Radiant drift: see Table 6; V : 42 km/s r : 3.0; TFC : alpha = 088°, delta = +20° and alpha = 135°, delta = +48° (beta > 40° N); or alpha = 120°, delta = -03° and alpha = 084°, delta = +10° (beta < 40° N).
Only low rates are likely from this minor source, making accurate visual
plotting, telescopic or video work essential, particularly because the meteors
are normally faint. The shower's details, even including its radiant position,
are rather uncertain. Recent IMO data showed only weak signs of a maximum as
indicated above. Telescopic results suggest a later maximum, around December 15-
16 (sol ~ 264°) from a radiant at alpha = 117°, delta = +20°.
This is quite a good year for making observations, as the waxing gibbous Moon
sets between local midnight and 1h across the world on December 9, while the
radiant is on-show virtually all night, culminating about 1h30m local time.
σ-Hydrids
Active : December 3-15; Maximum : December 12 (sol = 260°); ZHR : 2; Radiant : alpha = 127°, delta = +02°; Radiant drift: see Table 6; V : 58 km/s r : 3.0; TFC : alpha = 095°, delta = 00° and alpha = 160°, delta = 00° (all sites, after midnight only).
Although first detected in the 1960s by photography, sigma-Hydrids are
typically swift and faint, and rates are generally very low, close to the visual
detection threshold. Since their radiant, a little over 10° east of the
star Procyon (α Canis Minoris), is near the equator, all observers can
cover this shower. The radiant rises in the late evening hours, but is best
viewed after local midnight. Although the Moon is only three days before full
for their predicted peak, there remains a short dark-sky observing window after
moonset and before dawn, particularly north of the equator, for observers to
take advantage of. Recent data indicates the maximum may happen up to six days
earlier than this theoretical maximum, which would be very much more favourable
for Moon-free watching. The shower would benefit from visual plotting,
telescopic or video work to pin it down more accurately.
Ursids
Active : December 17-26; Maximum : December 22, 13h UT (sol = 270.7°); ZHR : 10 (occasionally variable up to 50); Radiant : alpha = 217°, delta = +76°; Radiant drift: see Table 6; V : 33 km/s r : 3.0; TFC : alpha = 348°, delta = +75° and alpha = 131°, delta = +66° (beta > 40° N); alpha = 063°, delta = +84° and alpha = 156°, delta = +64° (β 30° to 40° N).
A very poorly observed northern-hemisphere shower, but one which has
produced at least two major outbursts in the past 60 years, in 1945 and 1986.
Several other rate enhancements, recently in 1988, 1994 and 2000, 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 sol = 270°8, for instance,
which might suggest a slightly later maximum time in 2005 of December 22, 15h20m
UT, while the 2000 enhancement was seen surprisingly strongly (rm EZHR ~ 90) by
video at sol = 270°78 (equivalent to 2005 December 22, 15h UT), although the
visual enhancement was much less, rm ZHR ~ 30. 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
waning gibbous Moon will rise around 23h local time on December 22, so
conditions will not be perfect for seeing whatever happens this time. The
expected peaks favour northerly sites between central Asia eastwards across the
Pacific Ocean to western North America.
[image:672]
Figure 15
- Radiant position of the Ursids.