November 12, 2012 Leave a comment
The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.
As seen from the northern hemisphere, meteor rates continue to be strong in November. While no major activity is expected this month, the two Taurid radiants plus the Leonids keep the skies active. The addition of strong sporadic rates make November one of the better months to view meteor activity from north of the equator. Skies are fairly quiet as seen from the
southern hemisphere this month. Activity from the three showers mentioned above may be seen from south of the equator, but the sporadic rates are much lower than those seen in the northern hemisphere.
During this period the moon reaches its new phase on Tuesday November 13th. At this time the moon is located near the sun and cannot be seen at night. This weekend the waning crescent moon will rise during the late morning hours, but it will rise so late and be so thin that it will not interfere with meteor observing. As the week progresses the moon will enter the evening sky but will set shortly after dusk, not causing any problems for watching meteor activity. The estimated total hourly meteor rates for evening observers this week is near five for observers located at mid-northern latitudes and three for observers in mid-southern latitudes. For morning observers the estimated total hourly rates should be near twenty from the mid-northern hemisphere and twelve 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.
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 November 10/11. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.
The following radiants are expected to be active this week:
Remnants from the famous Andromedid (AND) shower, noted for intense storms during the 19th century, may still be seen throughout November. The current position of this large radiant is 01:32 (023) +31 . This position lies on the Pisces/Triangulum border, very close to the large, but faint spiral galaxy known as M33. If you are not familiar with M33, then the nearest bright star is second magnitude Mirach (Beta Andromedae), which lies five degrees to the northwest. The radiant is so diffuse that Andromedid meteors may be seen coming from southern Andromeda, Triangulum, and northwestern Aries as well as eastern Pisces. Visual activity is expected to be low, but detectable. An inconspicuous maximum occurs on November 9, when this source is the 5th most active radiant in the sky. The Andromedid meteors are best seen near 2200 (10pm) local standard time (LST), when the radiant lies on the meridian and lies highest in the sky. At 19km/sec., the average Andromedid will appear as a v
ery slow moving meteor.
The Northern Taurid (NTA) radiant is the most active source of meteor activity this week, producing 3-4 shower members per hour, depending on your location. The radiant is centered at 03:52 (058) +22. This area of the sky lies in western Taurus just one degree south of the famous naked eye open cluster known as the Pleiades or the Seven Sisters. The radiant is best placed near 0100 LST, 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. 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 04:00 (060) +15. This position lies in western Taurus, eight degrees southeast of the famous naked eye open cluster known as the Pleiades or the Seven Sisters. This radiant is also best placed near 0100 LST, 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 , no matter your location. With an entry velocity of 29 km/sec., the average Southern Taurid meteor would be of slow velocity.
The November Orionids (NOO) may be seen in small numbers beginning this week. The peak for this radiant is not until November 30th, so rates would be less than than one shower member per hour, no matter your location. The radiant is located at 05:08 (077) +16. This area of the sky is located on the Orion/Taurus border, seven degrees east of the first magnitude orange star Aldebaran (Alpha Tauri). This location is close to the Taurid complex, but far enough east to be distinguishable. The faster velocity of the November should help distinguish these meteors from the slower, but more numerous Taurids. The radiant is best placed for viewing near 0200 LST when it lies on the meridian and is highest above the horizon. With an entry velocity of 44 km/sec., the November Orionids would be of medium speed.
The Orionids (ORI) are still active but rates are slowing falling with each passing night. The radiant located at 07:28 (112) +16. This area of the sky is located in southern Gemini, twelve degrees east of the second magnitude star Alhena (Gamma Geminorum). The radiant is best placed for viewing near 0400 LST when it lies on the meridian and is highest above the horizon. 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.
Studies of the IMO video database by Sirko Molau and Juergen Rendtel has revealed a radiant active in the constellation of Cancer this time of year. Rates are weak but detectable under moonless skies. The Zeta Cancrids (ZCN) are active throughout November but activity dates and radiant positions are poorly determined. During this period the radiant lies near 08:24 (126) +08. This area of the sky is located in southern Cancer, one degree southeast of the third magnitude star Al Tarf (Beta Cancri). This area of the sky may be more easier found using the “head” of Hydra as a guide, as it lies only five degrees to the southeast. The radiant is best placed for viewing near 0500 LST when it lies on the meridian and is highest above the horizon. With an entry velocity of 70 km/sec., most activity from this radiant would be swift. These meteors can be seen equally well from either side of the equator.
The Leonids (LEO) are now the second most active radiant in the sky, producing 1-2 shower members per hour during the last couple of hours before dawn. The radiant is currently located at 10:00 (150) +24. This position lies in northwestern Leo, within the “sickle” of Leo, three degrees west of the third magnitude star Adhafera (Zeta Leonis). The Leonid radiant is best placed during the last hour before morning twilight when the radiant lies highest in a dark sky. Leonids may be seen from the southern hemisphere but the viewing conditions are not quite as favorable as those north of the equator.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately eleven 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 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 summary of the expected activity this week. Rates and
positions are exact for Saturday night/Sunday morning, but may be used all week.
Andromedids (AND) – 01:32 (023) +31 Velocity 19km/sec
Northern Hemisphere – 1 per hr Southern Hemisphere – <1 per hour
Northern Taurids (NTA) – 03:52 (058) +22 Velocity 29km/sec
Northern Hemisphere – 4 per hr Southern Hemisphere – 3 per hour
Southern Taurids (STA) -04:00 (060) +15 Velocity 29km/sec
Northern Hemisphere – 2 per hr Southern Hemisphere – 2 per hour
November Orionids (NOO) 05:08 (077) +16 Velocity 44km/sec
Northern Hemisphere – <1 per hr Southern Hemisphere – <1 per hour
Orionids (ORI) 07:28 (112) +16 Velocity 67km/sec
Northern Hemisphere – 1 per hr Southern Hemisphere – 1 per hour
Zeta Cancrids (ZCN) 08:24 (126) +08 Velocity 70km/sec
Northern Hemisphere – <1 per hr Southern Hemisphere – <1 per hour
Leonids (LEO) 10:00 (150) +24 Velocity 71km/sec
Northern Hemisphere – 2 per hr Southern Hemisphere – 1 per hour
American Meteor Society