(meteorobs) Meteor Activity Outlook for April 26-May 2, 2014

[Robert Lunsford]

During this period the moon reaches its new phase on Tuesday April 29th. At this time the moon will lie near the sun and will be invisible at night. This weekend the waning crescent moon will rise only during the late morning hours and will not cause any interference to potential meteor observers. The estimated total hourly meteor rates for evening observers this week is near 2 for observers situated at mid-northern latitudes and 3 for observers viewing from the southern tropics (latitude 25 S.). For morning observers the estimated total hourly rates should be near 7 for observers situated at mid-northern latitudes and 11 for observers viewing from the southern tropics. 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. 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 April 26/27. 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 sources of meteoric activity are expected to be active this week:

The last members of the Pi Puppids (PPU) are expected this weekend from a radiant located at 07:28 (112) -45. This area of the sky is located southern Puppis,  close to the position occupied by the third magnitude star Sigma Puppis. This area of the sky is best seen as soon as it becomes dark during the early evening hours. No matter your location, rates are expected to be low. Observers located in the tropical northern hemisphere may also see some activity but at latitudes north of 30 degrees north, the odds are against seeing any activity at all. Observers south of the equator are favored due to the southerly declination of the radiant.  At 18km/sec. the Pi Puppids would produce meteors of very slow velocity.

The Alpha Bootids (ABO) have appeared on radiant lists for many years now. The dates of activity and position of the radiant keep changing with additional knowledge about this source. The first detailed study of the ABO's was by Porubcan and Gavajdova in 1994, using Terentjeva's data of fireball orbits. The latest data is provided by the IMO Video Network which detected these meteors between April 26 and May 5. Activity was extremely weak on all nights but April 27 (solar longitude 037) when this source was the 3rd most active in the sky. Potential observers of these meteors should therefore concentrate on the night of April 26/27. The radiant was found to be near 13:50 (272) +07, which lies on the border of Bootes and Virgo, 12 degrees southwest of the brilliant orange star known as Arcturus (Alpha Bootis). This area of the sky is best placed near midnight LDT, when it lies on the meridian and lies highest above the horizon. Rates will most likely be low but these meteors will be distinctive due to their very slow velocity of 18 km/sec.

The center of the large Anthelion (ANT) radiant is currently located at 15:16 (229) -18. This position lies in central Libra, only 3 degrees southeast of the bright planet Saturn. These meteors may be seen all night long but the radiant is best placed near 0200 LDT when it lies on the meridian and is positioned highest in the sky. Due to the large radiant area, meteors from this source may also appear to radiant from the constellation of Serpens Caput, northwestern Scorpius, eastern Hydra, and eastern Virgo as well as Libra. Rates at this time should be near 1 per hour no matter your location. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.

The Nu Cygnids (NCY) are active from April 2nd through May 4th with maximum activity occurring on April 18th. The radiant is currently located near the position of 21:24 (321) +46. This position lies in northeastern Cygnus, 6 degrees east of the 1st magnitude star known as Deneb (Alpha Cygni). This position is best suited for viewing from the northern hemisphere where the radiant lies high in the northeastern sky during the last couple of hours before dawn. During the same time of night, as seen from the southern tropics, the radiant lies low in the northeast therefore diminished activity will be seen from the southern hemisphere. Since we are now a week past maximum activity, rates are expected to be low no matter your location. At 44 km/sec. these meteors would have a medium-swift velocity.

The Eta Aquariids (ETA) are particles from Halleys Comet, produced in Earth-crossing orbits many centuries ago. We pass closest to these orbits from May 5 through the 9th. During this period the Eta Aquariids are at their best, capable of producing ZHRs of 60. The actual visible rates are most often less than half this figure due to the low altitude of the radiant at dawn. Observed hourly rates at maximum normally vary from zero at 60 degrees north latitude to 30 near the equator and back down to near zero again in Antarctica, where the radiant elevation is again very low. Hourly rates this weekend will most likely be 1-2 per hour. Rates will slowly increase as the week progresses as we approach the May 7 maximum. The radiant is currently located at 22:14 (334) -03. This area of the sky is located in northern Aquarius, two degrees southwest of the fourth magnitude star Gamma Aquarii. The best time to view this activity is during the hour before the start of morning twilight, when the radiant lies highest in a dark sky. With the radiant low in the east it would be best to face halfway up in the sky in that same direction. If the radiant has sufficient altitude Eta Aquariid meteors can also be seen shooting down toward the eastern horizon. With an entry velocity of 68 kilometers per second, a majority of these meteors will appear to move swiftly with a high percentage of the bright meteors leaving persistent trains. Surprisingly, this shower produces very few fireballs.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 5 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 1 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 8 per hour as seen from rural observing sites and 2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.

The list below presents a list of radiants that are expected to be active this 
week. Rates and positions are exact for Saturday night/Sunday morning except 
where noted in the discussion of each radiant. 
 
Pi Puppids (PUP) - 07:28 (112) -45   Velocity - 18km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr.

Alpha Bootids (ABO) - 13:50 (272) +07   Velocity - 18km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr.
 
Anthelions (ANT) - 15:16 (229) -18   Velocity - 29km/sec. 
Northern Hemisphere - 1 per hr.   Southern Hemisphere - 1 per hr 
 
Nu Cygnids (NCY) - 21:24 (321) +46  Velocity - 44km/sec. 
Northern Hemisphere -< 1 per hr.   Southern Hemisphere - <1 per hr. 
 
Eta Aquariids (ETA) - 22:14 (334) -03  Velocity - 68km/sec. 
Northern Hemisphere - 1 per hr.   Southern Hemisphere - 2 per hr. 
 
Clear Skies! 
Robert Lunsford 	 
American Meteor Society