(meteorobs) Meteor Activity Outlook for October 20-26, 2012

[Robert Lunsford]

During this period the moon reaches its first quarter phase on Sunday October 21st. At this time the moon is located ninety degrees east of the sun and well set near 2300 (11pm) local daylight time (LDT). As the week progresses the waxing gibbous moon will set later and later in the morning, interfering with meteor observing. The estimated total hourly meteor rates for evening observers this week is near three for observers located at mid-northern latitudes and two for observers in mid-southern latitudes. For morning observers the estimated total hourly rates should be near thirty eight from the mid-northern hemisphere and twenty seven from the mid-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. Rates during the evening hours are reduced this week due to moonlight.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning October 20/21. 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 radiants are expected to be active this week:

The Northern Taurids (NTA) are now active from a large radiant centered at 02:40 (040) +19, which lies in central Aries, eight degrees southeast of the second magnitude star Hamal (Alpha Arietis). The radiant is best placed near 0200 local daylight time (LDT), when it lies highest above the horizon. Maximum activity is not expected until November 13, so current rates would be 1-2 per hour, no matter your location. Meteors from the Northern Taurids strike the atmosphere at 29km/sec., which would produce meteors of slow velocity.  You must face in the general direction of the north and south Taurid radiants in order to tell them apart.

The Southern Taurid (STA) radiant is currently located at 02:48 (042) +11. This position lies near on the Cetus/Aries border, very close the the fourth magnitude star Mu Ceti. This radiant is best placed near 0200 local daylight time (LDT), when it lies on the meridian and is located highest in the sky. Maximum occurred on October 9th, so rates would now be near two per hour when the radiant lies high in the sky. With an entry velocity of 29 km/sec., the average Southern Taurid meteor would be of slow velocity.

The Orionids (ORI) reach maximum activity on mornings of October 21st and 22nd. The radiant is currently located at 06:20 (095) +16, which is in the northeastern Orion, four degrees west of the second magnitude star Alhena (Gamma Geminorum). The radiant is best placed for viewing near 0500 when it lies on the meridian and is highest above the horizon. At this time of night one should be able to count at least 20 shower members per hour from rural locations. Good rates can actually be seen any time during the morning hours. Orionid meteors are equally well seen either side of the equator. With an entry velocity of 67 km/sec., most activity from this radiant would be swift. This display does not have a sharp peak so activity seen after moon set after the 22nd should be good. Unfortunately the moon will begin to interfere late in the week.

The Epsilon Geminids (EGE) are active all month long with low hourly rates. Even at maximum activity only three shower members per hour are expected. Recent research by the IMO has indicated an earlier maximum of October 15th, rather than October 19th. The radiant position is currently located at 06:56 (104) +28. This position lies in northern Gemini, four degrees northeast of the fourth magnitude star Mebsuta (Epsilon Geminorum). The radiant is also best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. Rates would be near two per hour as seen from the northern hemisphere and less than one per hour as seen south of the equator. With an entry velocity of 70 km/sec., most activity from this radiant would be swift.

The Leonis Minorids (LMI) are active from October 16-27 with maximum activity occurring on October 23rd. This radiant is currently located at 10:36 (159) +37, which places it in northeast Leo Minor, four degrees northeast of 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 ten sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near two per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near five 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. Rates during the evening hours are reduced this week due to moonlight.

The list below presents a summary of the expected activity this week. Rates and
positions are exact for Saturday night/Sunday morning, but may be used all week.

Northern Taurids (NTA) - 02:40 (040) +19   Velocity 29km/sec
Northern Hemisphere - 2 per hr   Southern Hemisphere - 2 per hour

Southern Taurids (STA) -02:48 (042) +11   Velocity 29km/sec
Northern Hemisphere - 2 per hr   Southern Hemisphere - 2 per hour

Orionids (ORI) 06:20 (095) +16   Velocity 67km/sec
Northern Hemisphere - 20 per hr   Southern Hemisphere - 18 per hour

Epsilon Geminids (EGE) 06:56 (104) +28   Velocity 70km/sec
Northern Hemisphere - 2 per hr   Southern Hemisphere - <1 per hour

Leonis Minorids (LMI) - 10:36 (159) +37   Velocity 60km/sec
Northern Hemisphere - 2 per hr   Southern Hemisphere - <1 per hour

Clear Skies!
Robert Lunsford
American Meteor Society