(meteorobs) Meteor Activity Outlook for October 17-23, 2009

[Robert Lunsford]

Meteor activity in general increases in October when compared to September.
A major shower (the Orionids) is active most of the month along with several
minor showers. Both branches of the Taurids become more active as the month
progresses, providing slow, graceful meteors to the nighttime scene. The
Orionids are the big story of the month reaching maximum activity on the
22nd. This display can be seen equally well from both hemispheres which
definitely helps out observers located in the sporadic-poor southern
hemisphere this time of year.

During this period the moon reaches its new phase on Sunday October 18th. At
this time the moon lies near the sun and is invisible at night. Later in the
period the waxing crescent moon will enter the evening sky but will not
interfere with meteor observing. The estimated total hourly rates for
evening
observers this week is near five as seen from the northern hemisphere and
two from the southern hemisphere. For morning observers the estimated total
hourly rates should be near twenty five from the northern hemisphere and
fifteen as seen from the southern hemisphere. The actual rates will also
depend on factors such as personal light and motion perception, local
weather conditions, alertness and experience in watching meteor activity.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning October 17/18. These positions do not change greatly
day to day so the listed coordinates may be used during this entire period.
Most star atlases (available at science stores and planetariums) will
provide maps with grid lines of the celestial coordinates so that you may
find out exactly where these positions are located in the sky. A planisphere
or computer planetarium program is also useful in showing the sky at any
time of night on any date of the year. Activity from each radiant is best
seen when it is positioned highest in the sky, either due north or south
along the meridian, depending on your latitude. It must be remembered that
meteor activity is rarely seen at the radiant position. Rather they shoot
outwards from the radiant so it is best to center your field of view so that
the radiant lies at the edge and not the center. Viewing there will allow
you to easily trace the path of each meteor back to the radiant (if it is a
shower member) or in another direction if it is a sporadic. Meteor activity
is not seen from radiants that are located below the horizon. The positions
below are listed in a west to east manner in order of right ascension
(celestial longitude). The positions listed first are located further west
therefore are accessible earlier in the night while those listed further
down the list rise later in the night.

The following showers are expected to be active this week.

A new radiant has been discovered in Ursa Minor which is active during this
period. The October Ursa Minorids (OUI) are active from October 16-28, with
maximum occurring on the 24th. The current radiant position lies at 18:40
(280) +76. This position lies in northern Draco near the faint star 50
Draconis. The radiant is best placed just as soon as it becomes dark, when
it lies highest in a dark sky. Meteors from the October Ursa Minorids strike
the atmosphere at 28km/sec., which would produce meteors of slow velocity.
Expected rates would be less than one per hour, as seen from the northern
hemisphere. Activity from this shower is not visible in the southern
hemisphere due to the high northerly location of the radiant.

A recent study of video radiants by Sirko Molau has revealed that activity
from the Northern Taurids (NTA) does not begin until October 19th. This is
nearly one month after pervious dates. Maximum activity does not occur until
November 13th so current rates will be low, lower than its southern
counterpart until late in the month. The radiant position lies at 02:32
(038) +19, which lies in central Aries, six degrees southeast of the second
magnitude star Hamal (Alpha Arietis). The radiant is best placed near 0130
LDT, when it lies highest above the horizon. Meteors from the Northern
Taurids strike the atmosphere at 29km/sec., which would produce meteors of
slow velocity. Expected rates would be less than one per hour, no matter
your location.

The center of the large Southern Taurid (STA) radiant lies at 02:34 (038)
+10. This position lies on the Aries/Cetus border, three degrees west of the
fourth magnitude star Upsilon Ceti. Since the radiant is so large, any
meteor from eastern Pisces, northern Cetus, or southern Aries could be a
candidate for this shower. The radiant is best placed near the meridian at
0130 LDT, but activity may be seen all night long. Striking the atmosphere
at 29 km/sec., the average Southern Taurid meteor travels slowly through the
skies. Rates should be near three per hour no matter your location.

A new radiant has been discovered in Aries which is active during this
period. The Sigma Arietids (SSA) are active from October 12-19, with maximum
occurring on the 19th. The current radiant position lies at 03:26 (051) +22,
which lies on the Aries/Taurus border, lying directly between the Pleiades
star cluster and the fourth magnitude star Delta Arietis. The radiant is
best placed near 0230 LDT, when it lies highest above the horizon. Meteors
from the Sigma Arietids strike the atmosphere at 45km/sec., which would
produce meteors of average velocity. Expected rates would be less than one
per hour, no matter your location.

The Orionids (ORI) are predicted to peak on Thursday morning October 22nd.
This is a broad maximum so activity on the 21st and 23nd should also be
good. The radiant is currently located at 06:12 (93) +15. This position lies
in northwestern Orion one degree north of the fourth magnitude star Xi
Orionis. The radiant rises near 2300 LDT and is best placed on the meridian
near 0530 LDT. With maximum activity predicted for October 22, current rates
for all locations would be near five per hour as seen after midnight. At
66km/sec., the average Orionid is swift.

The Epsilon Geminids (EGE) are active from October 16th through the 27th.
Maximum activity occurs on the 19th. The radiant is currently located at
06:44 (101) +28. This position lies in northwestern Gemini, three degrees
northwest of the third magnitude star Epsilon Geminorum. This position is
also close to the Orionid radiant. Care must taken for correct shower
association. The Orionids will be far more numerous. Current rates are most
likely less than one per hour. The radiant is best placed near 0600 LDT,
when it lies highest above the horizon. At 70km/sec., the average Epsilon
Geminid is swift.

Activity from Ursa Major this time of year has been known for several years
now. Recent studies by Sirko Molau has provided more precise data on this
activity. The October Ursa Majorids (OCU) are active from October 12-19,
with maximum occurring on the 15th. The current radiant position lies at
09:58 (149) +63, which lies in western Ursa Major, four degrees north of the
third magnitude star Nu Ursae Majoris. The radiant is best placed during the
last dark hour before the start of morning twilight, when it highest above
the horizon in a dark sky. Meteors from the October Ursa Majorids strike the
atmosphere at 53km/sec., which would produce meteors of medium-swift
velocity. Expected rates would be less than one per hour, no matter your
location. This activity is not visible from the southern hemisphere due to
the high northerly declination of the radiant.

The Leonis Minorids (LMI) are active from October 16-27 with maximum
activity occurring on October 23rd. ZHR's are usually low but the radiant is
far removed from the Orionids and Epsilon Geminids so that any possible
shower members should be easily identified. Hourly rates would be less than
one this week. This radiant is currently located at 10:21 (155) +37, which
places it in northeastern Leo Minor, very close to the fourth magnitude star
Beta Leonis Minoris. The radiant is best placed just before dawn when it
lies highest in a dark sky. This shower is better situated for observers
situated in the northern hemisphere where the radiant rises far higher into
the sky before the start of morning twilight. At 60km/sec., the average
Leonis Minorid is swift.

As seen from the mid-northern hemisphere (45N) one would expect to see
approximately fifteen Sporadic meteors per hour during the last hour before
dawn as seen from rural observing sites. Evening rates would be near four
per hour. As seen from the mid-southern hemisphere (45S), morning rates
would be near four per hour as seen from rural observing sites and one per
hour during the evening hours. Locations between these two extremes would
see activity between the listed figures.

The table below presents a condensed version of the expected activity this
week. Rates and positions are exact for Saturday night/Sunday morning.

October Ursa Minorids (OUI)  - 18:40 (280) +76 Velocity - 28km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr.

Northern Taurids (NTA)   - 02:32 (038) +19  Velocity - 29km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr.

Southern Taurids (STA)  - 02:34 (038) +10  Velocity - 29km/sec.
Northern Hemisphere - 3 per hr. Southern Hemisphere - 3 per hr.

Sigma Arietids (SSA) - 03:26 (051) +22   Velocity - 45km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr.

Orionids (ORI)  - 06:12 (93) +15   Velocity - 67km/sec.
Northern Hemisphere - 5 per hr. Southern Hemisphere - 5 per hr.

Epsilon Geminids (EGE)  - 06:44 (101) +28   Velocity - 70km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr.

October Ursa Majorids (OCU)  - 09:58 (149) +63   Velocity - 53km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr.

Leonis Minorids (LMI)  - 10:21 (155) +37   Velocity - 60km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr.

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2009

Clear Skies!
Robert Lunsford
American Meteor Society