(meteorobs) Meteor Activity Outlook for October 22-28, 2011

[Robert Lunsford]

During this period the moon reaches its new phase on Wednesday October 26th. At this time the moon will lie near the sun and will be invisible at night. This weekend the waning crescent moon will rise during the late morning hours and will not interfere with meteor observing. The estimated total hourly rates for evening observers this week is near four as seen from the northern hemisphere and three as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near thirty three as seen from mid-northern latitudes and twenty eight from mid-southern latitudes. 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 (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning October 22/23. 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 by Sirko Molau and Juergen Rendtel in Draco 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 18:18 (275) +75. This position lies in eastern Draco two degrees north of the faint star Chi Draconis. Older radiant positions were a bit further west in Ursa Minor.  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.

The Northern Taurids (NTA) are now active from a large radiant centered at 02:48 (042) +20, which lies in central Aries, six degrees west of the fourth magnitude star Delta Arietis. The radiant is best placed near 0200 local daylight time (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 near two per hour, no matter your location.

The center of the Southern Taurid (STA) radiant now lies 02:51 (043) +11. This position lies on the Aries/Cetus border, three degrees east of the fourth magnitude star Mu Ceti. The radiant is best placed near the meridian at 0200 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 two per hour no matter your location.

A new radiant has been discovered in Taurus which is active during this period. The Eta Taurids (ETT) are active from October 24 through November 3, with maximum occurring on the 24th. At maximum, the  radiant position lies at 03:42 (056) +24, which lies in western Taurus in the area of sky occupied by the famous Pleiades star cluster. The radiant is best placed near 0300 LDT, when it lies highest above the horizon. Meteors from the Eta Taurids strike the atmosphere at 47km/sec., which would produce meteors of average velocity. Expected rates would be less than one per hour, no matter your location.

The Orionids (ORI) reach maximum activity on morning of October 22nd. Rates are expected to peak between 10-20 shower members per hour on that morning. Moonlight from the waning crescent moon will reduce activity slightly. The radiant is currently located at 06:28 (97) +16. This position lies in western Gemini, close to the second magnitude star Alhena (Gamma Geminorum). The radiant is best placed near 0500 LDT, when it lies highest above the horizon. At 67km/sec., the average Orionid is swift.

The Epsilon Geminids (EGE) are active from October 16th through the 27th. Maximum activity occurred on the 19th. The radiant is currently located at 07:02 (105) +27. This position lies in central Gemini, three degrees northeast of the third magnitude star Epsilon Geminorum. This position is also close to the Orionid radiant so care must taken for correct shower association, especially since they have similar velocities. The Orionids will be more numerous. Current rates are near 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.

Recent studies by Sirko Molau and Juergen Rendtel have revealed a radiant in Canis Minor that is active this time of year. Old radiant positions placed it within the borders of Cancer. The Beta Cancrids (BCN) are active from October 25 through November 3, with maximum occurring on the 27th. The radiant position at maximum lies at 07:22 (111) -06, which lies in southwestern Canis Minor, three degrees west of the brilliant zero magnitude star Procyon (Alpha Canis Minoris. The radiant is best placed near 0600 LDT, when it lies highest above the horizon.Meteors from the Beta Cancrids strike the atmosphere at 65km/sec., which would produce meteors of swift velocity. Expected rates would be less than one per hour, no matter your location.

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 should be near one this weekend. This radiant is currently located at 10:43 (161) +36, which places it in northeastern Leo Minor, two degrees east 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 three 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 two per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.

The list 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) - 18:18 (275) +75    Velocity - 28km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr

Northern Taurids (NTA) - 02:48 (042) +20   Velocity - 29km/sec.
Northern Hemisphere - 2 per hr. Southern Hemisphere - 2 per hr

Southern Taurids (STA) - 02:51 (043) +11   Velocity - 27km/sec.
Northern Hemisphere - 2 per hr. Southern Hemisphere - 2 per hr

Eta Taurids(ETT) - 03:42 (056) +24   Velocity - 47km/sec.
Northern Hemisphere -<1 per hr. Southern Hemisphere - <1 per hr

Orionids (ORI) - 06:28 (97) +16   Velocity - 67km/sec.
Northern Hemisphere -15 per hr. Southern Hemisphere - 15 per hr

Epsilon Geminids (EGE) - 07:02 (105) +27   Velocity - 70km/sec.
Northern Hemisphere - 1 per hr. Southern Hemisphere - 1 per hr

Beta Cancrids (BCN) - 07:22 (111) -06   Velocity - 65km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr

Leonis Minorids (LMI) - 10:43 (161) +36   Velocity - 60km/sec.
Northern Hemisphere - 2 per hr. Southern Hemisphere - 2 per hr

Clear Skies!
Robert Lunsford
American Meteor Society