(meteorobs) Meteor Activity Outlook for November 21-27, 2015

[Robert Lunsford]

During this period the moon reaches its full phase on Wednesday November 25th. On that date the moon will be located opposite the sun and will lie above the horizon all night long. This weekend the waxing gibbous  moon will set during the early morning hours and will allow a few hours of dark skies before the onset of dawn. It is during this window of opportunity after moonset you should try and view the meteor activity this week. The estimated total hourly meteor rates for evening observers this week is near 3 as seen from mid-northern latitudes (45N) and 2 as seen from tropical southern locations (25S). For morning observers the estimated total hourly rates should be near 20 as seen from mid-northern latitudes (45N) and 13 as seen from tropical southern locations (25S). 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 during this period due to moonlight. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brightest meteors will be visible from such locations.

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 21/22. 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.

These sources of meteoric activity are expected to be active this week.

The Northern Taurids (NTA) are active from a large radiant centered at 04:28 (067) +24. This position lies in north-central Taurus, 8 degrees north of the bright orange first magnitude star known as Aldebaran. The radiant is best placed near midnight local standard time (LST), when it lies highest above the horizon. Meteors from the Northern Taurids strike the atmosphere at 27km/sec., which would produce meteors of slow velocity. Expected rates would be near 2 per hour as seen from the northern hemisphere and 1 per hour as seen from south of the equator.

The November Orionids (NOO) are active from a radiant located at 05:44 (086) +16. This area of the sky is located in northern Orion, 4 degrees north of the first magnitude orange star Betelgeuse (Alpha Orionis). The peak for this radiant is not until November 28th, so current rates would be 1-2 shower members per hour, no matter your location. This location is close to the Northern Taurids , but far enough east to be distinguishable. The faster velocity of the November Orionids should help distinguish these meteors from the slower 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 Alpha Monocerotids (AMO) are a variable shower known for strong but short outbursts in 1985 and 1995. In most years just a few of meteors from this source are seen near November 22nd. Activity is usually limited to November 21-23 with a radiant located at 07:52 (118) +01. The area of the sky is located in southeastern Canis Minor just 5 degrees southeast of the brilliant 0 magnitude star known Procyon (Alpha Canis Minoris). The radiant was thought to originate in nearby Monoceros but recent refinements have placed it within Canis Minor. These meteors are best seen near 0400 LST, when the radiant lies highest above the horizon. With an entry velocity of 68 km/sec., most activity from this radiant would be of swift speed.

The Leonids (LEO) are still the most active radiant in the sky, but rates are dwindling with each passing night. Expect rates this weekend to be near 3 per hour falling to near 1 per hour by the end of the week. The radiant is currently located at 10:16 (154) +20. This position lies in northwestern Leo, very close to the position occupied by the second magnitude double star Algeiba (Gamma 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. With an entry velocity of 70 km/sec., most activity from this radiant would be of swift speed with numerous persistent trains on the brighter meteors.

The November Iota Draconids (NID) were discovered by Dr. Peter Brown during his 7 year meteoroid stream survey using the Canadian Meteor Orbit Radar. This source is active from November 11 through the 1st of December with maximum activity occurring on November 21st. The radiant is currently located at 12:36 (189) +69. This area of the sky lies in western Draco, close to the position occupied by the 4th magnitude star known as Kappa Draconis. The radiant is best placed during the last hour before morning twilight when the radiant lies highest in a dark sky. Expect rates of 1 per hour at maximum as seen from the northern hemisphere. Due to the high northerly declination of the radiant these meteors are not visible from most of the southern hemisphere. Only southern equatorial regions would have any chance of seeing activity from this source. Meteors from the November Iota Draconids strike the atmosphere at 41km/sec., which would produce meteors of medium velocity.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 12 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 2 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 9 per hour as seen from rural observing sites and 1 per hour during the evening hours. Evening rates are reduced this week due to bright moonlight. Locations between these two extremes would see activity between the listed figures. 

The list below offers the information from above in a condensed form. Rates and 
positions are exact for Saturday night/Sunday morning except where noted in the 
shower descriptions. 
 
Northern Taurids (NTA) -  04:28 (067) +24  Velocity - 29km/sec. 
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 1 per hr 
 
November Orionids (NOO) - 05:44 (086) +16  Velocity - 44km/sec. 
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 1 per hr 
 
Alpha Monocerotids (AMO)  -  07:36 (114) +05  Velocity - 68km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr 
 
Leonids (LEO)  -  10:16 (154) +20  Velocity - 70km/sec. 
Northern Hemisphere - 3 per hr.   Southern Hemisphere - 2 per hr 
 
Nov. Iota Draconids (NID)  -  12:36 (189) +69  Velocity - 41km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr 
 
Clear Skies! 
Robert Lunsford 	 
American Meteor Society