Meteor Activity Outlook for May 1-7, 2010

May is a fairly slow month for meteor activity. The Eta Aquariids are very active the first two weeks of the month then fade as the month progresses. The only other showers active this month are the weak Nu Cygnids, the Eta Lyrids, and the Antihelion radiant. These will add only 1-2 meteors per hour to the total count. Sporadic rates are low but steady as seen from the mid-northern hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere (45 S) continue to rise this month toward a maximum in July.

During this period the moon reaches its last quarter phase on Wednesday 6th. At this time the moon lies ninety degrees west of the sun and rises near 0100 local daylight time (LDT). This weekend the waning gibbous moon will rise during the late evening hours, effectively ruining your chance of seeing good meteor activity the remainder of the night. Conditions improve slightly with each passing night as the moon's phase lessens and it rises later and later. The estimated total hourly rates for evening observers this week is near two for northern observers and three for those viewing from south of the equator. For morning observers the estimated total hourly rates should be near seven from the northern hemisphere and twelve as seen from the 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. Morning rates are reduced due to moonlight.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning May 1/2. 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:

The wide Antihelion (ANT) radiant is now centered at 15:36 (234) -19. This area of the sky lies in eastern Libra, seven degrees northwest of the second magnitude star Dschubba (Delta Scorpii). This radiant is best placed near 0200 local daylight time (LDT) when it lies on the meridian and is located highest in the sky. Due to the large size of this radiant, any meteor radiating from extreme eastern Hydra, Libra, northern Lupus, or western Scorpius could be a candidate for this shower. Rates at this time should be near one per hour as seen from the northern hemisphere and two per hour as seen from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.

The team of Sirko Molau and Juergen Rendtel have discovered a weak radiant active at this time in the constellation of Cygnus. Video data shows that the Nu Cygnids (NCY) are active from April 18th through May 7th. Maximum activity occurred on the morning of April 20th. The radiant is currently located at 21:48 (327) +48. This position lies in northeastern Cygnus close to the faint star known as Pi 2 Cygni. The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. At 42km/sec. the Nu Cygnids would produce meteors of medium velocity. Expected rates are less than one per hour. Due to the northerly declination of the radiant, these meteors are not well seen from south of the equator.

The Eta Aquariids (ETA) are particles from Halley's 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 ZHR's of sixty. 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 25 near the equator and back down to near zero again in Antarctica, where the radiant elevation is very low. Hourly rates this weekend are anywhere from zero to five per hour depending on your latitude and observing conditions. Rates will increase significantly as the week progresses as we approach the May 7 maximum. The radiant is currently located at 22:24 (336) -02. This area of the sky is located in northern Aquarius, just south of the fourth magnitude star Gamma Aquarii. The best time to view this activity is just before the start of morning twilight, when the radiant lies highest in a dark sky. No matter your location these meteors will appear from the eastern sky and shoot in all directions. If the radiant has sufficient altitude Eta Aquariid meteors can also be seen shooting down toward the eastern horizon. With an entry velocity of 67 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 four sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near one per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near seven 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. Morning rates are reduced due to moonlight.

The table below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.