[Prev][Next][Index][Thread]
(meteorobs) Meteor Activity Outlook for October 19-25, 2001
The moon reaches its first quarter phase on Tuesday October 23th. This
weekend the moon will set during the late evening hours allowing a good
look at this week's Orionid shower. This period offers the last good
look at meteor activity before the moon becomes too much of a hindrance.
The estimated total hourly rates for evening observers this week should
be near 2 for those in the Northern Hemisphere and 1 for those in the
Southern Hemisphere. For morning observers the estimated total hourly
rates should be near 30 for the Northern Hemisphere and 20 for those
located in the Southern Hemisphere. These rates assume that you are
watching from rural areas away from all sources of light pollution. The
actual rates will also depend on factors such as personal light and
motion perception, local weather conditions, alertness and experience in
watching for meteor activity. Rates are slightly reduced due to
moonlight during the evening hours. The positions listed below are
exact for Saturday night/Sunday morning October 20/21. The positions do
not change greatly day to day so they may be used during this entire
period.
The Antihelion radiant is now located at 02:52 (043) +16. This area of
the sky is located in southeastern Aries 15 degrees southwest of the
Pleiades, a bright "dipper shaped" star cluster well known to all star
gazers. Any slow to medium speed meteor from eastern Aries, western
Taurus, or northeastern Cetus may be a good candidate for this shower.
This area of the sky is best placed near 0200 local daylight time (0100
local standard time) when it lies on the meridian. At this time expect
to see perhaps 3 per hour from all locations. We are now starting to see
a slight increase in the antihelion activity as the earth encounters
debris from comet 1P Encke. This additional material will push the
antihelion activity up to 5-10 meteors per hour during the first half of
November. Observers who share their reports with the International
Meteor Organization (I.M.O.) should label these meteors as "North or
South Taurids", depending if they appear to radiate from north or south
of the ecliptic.
The Orionids reach maximum activity on Sunday morning October 21. Unlike
most major annual showers this is not a sharp maximum so activity will
still be impressive a few days before and after the 21st. The maximum
hourly rates for the Orionids are typically 15-20 shower members but
occasionally approach 30 per hour if seen from rural observing sites
under optimum conditions. Most shower members are faint, being 3rd or
4th magnitude. Orionid fireballs do occur and a majority of the brighter
Orionids produce persistent trains. The radiant position lies at 06:20
(095) +16 which places it in extreme northeastern Orion 5 degrees west
of the 2nd magnitude star Alhena (Gamma Geminorum). With an entry
velocity of 66 km/sec. the Orionid meteors are swift when seen far from
the radiant and high in the sky. They will appear to move slower if seen
close to the radiant or near the horizon. Orionid activity is best seen
near 5am local daylight time, when the radiant is located on the
meridian and lies at its highest point in the sky. This shower is seen
equally well from both hemispheres.
The Epsilon Geminids are now active from a radiant located at 07:00
(105) +27. This area of the sky lies in central Gemini 10 degrees west
of the 1st magnitude star Pollux (Beta Geminorum). This position is
fairly close to the Orionid radiant so care should be taken with shower
association. Both showers produce similar appearing meteors. Maximum
activity was expected on the 18th so rates should be down to 1 meteor
per hour this week. These meteors are best seen just before dawn with
the radiant lies high in the eastern sky. This shower is slightly better
seen by those located in the Northern Hemisphere. Beyond 40 degrees
south the radiant does not climb very high in the northern sky and
activity will be limited.
The Delta Aurigids are at the end of their activity period. Expected
rates this week would be less than 1 shower member per hour as seen from
the Northern Hemisphere. The radiant is located at 07:04 (106) +50
which lies in a remote area of western Lynx This area of the sky lies
close to the zenith at dawn for observers in the mid Northern
Hemisphere. Shower activity is also visible from the south tropic
latitudes but not beyond 40 degrees south latitude. These meteors are
swift when seen far from the radiant and high in the sky. They will
appear to move more slowly if seen near the radiant or near the horizon.
The Northern Apex radiant is now located at 07:44 (116) +36. This
position lies in southwestern Lynx 5 degrees northeast of the 2th
magnitude star Castor (Alpha Geminorum). This area of the sky is best
placed for viewing during the last dark hour before dawn. Since this
radiant is diffuse any meteors from eastern Auriga, southwestern Lynx,
northwestern Cancer, or northeastern Gemini could be a good candidate.
As seen from the Northern Hemisphere this source should produce 2-3
meteors per hour during the last few hours before dawn. Rates seen from
the Southern Hemisphere would be much less at 0-1 per hour due to the
low radiant altitude seen south of the equator.
Like the antihelion radiant both apex radiants are active all year long
and travel approximately one degree eastward per day. Unlike the
antihelion debris these particles orbit the sun in a retrograde motion
opposite that of the earth and are most likely produced by unknown
comets. They strike the earth after their closest approach to the sun.
Since they are moving in opposite directions these particles strike the
earth at tremendous velocities often creating bright meteors with
persistent trains. These particles strike the earth on the morning side
of earth and are best seen just before morning twilight while the sky is
still perfectly dark. There are meteors with a zero inclination that
radiate precisely from the apex point on the ecliptic, exactly 90
degrees west of the sun. These meteors are rare though as the earth
orbits the sun it "sweeps clean" much of the material that shares the
same orbit. Much more debris is located just north and south of the
earth's orbit with slightly higher or lower inclinations. This creates
the northern and southern branches of the apex activity. Meteors from
both branches are normally included in the sporadic count but should
also be noted in some manner as to which branch of the apex complex they
appear to radiate.
The Southern Apex source lies exactly 30 degrees south of its northern
counterpart at 07:44 (116) +06. This position lies in central Canis
Minor only 1 degree northeast of the brilliant zero magnitude star
Procyon (Alpha Canis Minoris). Like the northern apex these meteors are
best seen toward dawn when the radiant lies highest above the horizon in
a dark sky. Any meteor from Canis Minor could be a candidate from this
source. Rates should be close to 1 per hour from most locations.
The Leo Minorids are listed among the radiants of the Dutch Meteor
Society. This is a weak shower only active for 3 nights centered on
October 24. The radiant position on that morning is 10:48 (162) +37,
which places it in eastern Leo Minor 6 degrees southeast of the 3rd
magnitude star Mu Ursae Majoris. This area of the sky is best placed
just before dawn in the northeastern sky. It is not well placed for
those living south of the equator. Rates may approach 1 shower member
per hour as seen from the Northern Hemisphere. These meteors are swift
when seen high in the sky.
The Sporadic rates for the Northern Hemisphere are now near 8 meteors
per hour during the last hours before dawn from rural observing sites.
This estimate and the morning estimate for the Southern Hemisphere does
not include the apex meteors listed above. During the evening hours
perhaps 2 random meteors can be seen per hour from the Northern
Hemisphere. Rates seen from the Southern Hemisphere are now at their
annual low with perhaps 4 random meteors being seen per hour during the
late morning hours and 1 per hour during the evening. Rates are slightly
reduced due to moonlight during the evening hours.
Clear Skies!
Robert Lunsford
AMS Visual Program Coordinator
The archive and Web site for our list is at http://www.meteorobs.org
If you are interested in complete links on the upcoming LEONIDS, see:
http://www.meteorobs.org/storms.html
To stop getting email from the 'meteorobs' list, use the Web form at:
http://www.meteorobs.org/subscribe.html