Meteor Activity Outlook for May 8-14, 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 new phase
on Friday May 14th. At this time the moon lies near the the sun and cannot be
seen at night. This weekend the waning crescent moon will rise during the early
morning hours but will not interfere with meteor observing as long as the observer
keeps it out of the field of their field of view. 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 twelve from the northern hemisphere and twenty 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.

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 May 8/9. 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 16:04 (241) -21. This
area of the sky lies in northwestern Scorpius just one degree to the southwest of the
third magnitude star Acrab (Beta 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 eastern
Libra, northern Lupus, southern Ophiuchus, 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 Eta Lyrids (ELY) are visible this week from a radiant located at
19:24 (291) +43. This position lies in extreme eastern Lyra, four degrees southwest
of the third magnitude star Delta Cygni. This shower is active from May 6 through
the 13th, peaking on May 10. Rates at maximum activity are near two per hour as
seen from the northern hemisphere. Unfortunately the Eta Lyrid radiant does not
rise very high in the northern sky as seen from the southern hemisphere so rates
seen from below the equator are minimal. Activity from this shower is best seen
during the last hour before dawn when the radiant is situated highest in a dark
sky. With an entry velocity of 43 km/sec., the average Eta Lyrid meteor would be
of medium speed.

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 ten per hour depending on your latitude and observing conditions. Rates will
slowly decrease as we move further away from the May 7 maximum. The radiant is
currently located at 22:40 (340) 00. This area of the sky is located in northeastern
Aquarius, just one degree east of the fourth magnitude star Eta 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
six 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 twelve 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 slightly 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.