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(meteorobs) Meteor Activity Outlook May 12-18, 2000
The moon is just now past first quarter and proceeding to its full phase
by the end of this period. This severely hampers any pre midnight
observing. In fact the moon now lies so high above the celestial equator
it is still well up in the sky past midnight even at first quarter. Once
the moon has set the one can set their sites on observing activity from
the antihelion area (ECL). This activity is provided by material that
orbits the sun in much the same plane as the planets (low inclination).
These particles are also inbound in their journey around the sun and are
therefore approaching perihelion. In our sky the center of this region
is currently located just north of the brilliant orange star Antares in
the constellation of Scorpius . The position for Saturday evening is
16:25 (248) -22. Any slow meteor from this general region of the sky
should be considered a member of this shower therefore any meteors from
Scorpius, Ophiuchus, and eastern Libra can be considered part of this
activity. Observers reporting directly to the IMO should label these
slow meteors "SAG".
Another source of morning activity could be at the Earth's apex, which
is the apparent direction in the sky in which the Earth is traveling.
These meteors are produced by particles orbiting in a retrograde
direction which is opposite the motion of the Earth. This head-on
collision creates a tremendous entry velocity for these particles and
they will usually appear to be moving quite fast against the starry
background. As seen in the sky the center of the apex (APX/SPO) source
on Saturday morning will be located in eastern Capricornus at 21:44
(323) -14 . Studies into this source have revealed that there are two
distinct areas located 15 degrees north and 15 degrees south of the
center that produce the most activity. The northern branch at 21:44
(323) +01 (in northwestern Aquarius) should be much easier to see for
Northern Hemisphere observers. The southern portion at 21:44 (323) -29
(in Pisces Austrinus) would be a good target for observers in the
Southern Hemisphere. As you can see the apex area is large and it would
seem that a large percentage of the sporadics would be involved. Yet
there are few studies involving these sources and it may prove
interesting to see just what approximate percent of the morning sporadic
activity is related to the apex. Be sure not to mix these swift meteors
up with the more active Eta Aquarids, whose radiant is located 25
degrees to the east.
The Eta Aquarid (ETA) radiant is still active but now located in western
Pisces. On Saturday morning the radiant will be located at 23:02 (344)
+02. The rates have now fallen to perhaps 5 shower members per hour.
This activity is still limited to the last two hours before morning
twilight as the radiant below the horizon most of the night. Be sure to
face toward the eastern half of the sky to see any of this activity.
Most Eta Aquarids will appear as fast streaks of light high in the sky
well away from the radiant.
Another source of minor activity this week may be the Beta Corona
Australids (CAU). This obscure radiant can be seen from north tropical
areas and the Southern Hemisphere. This is a very weak radiant that
needs plotting, photographic or video observing for correct shower
association. The peak activity is predicted on May 16 from an area
centered at 18:56 (282) -40. This is approximately 10 degrees south of
the "teapot" of Sagittarius. Any CAU's would appear slow near the
radiant and medium-fast far from it. It would be advisable to face
toward this general area of the sky in order to identify any of these
shower members.
Recent reports have indicated that the remnants of IRAS-Araki-Alcock
(1983) may be currently active. Normally a few meteors are seen from
this source between May 5-15. On May 7 rates as high as 6 per hour were
reported. It may be worth it to keep an eye out for any further
activity. On Saturday morning the radiant will be located near 19:20
(288) +44 which lies near the Lyra-Cygnus border. These meteors have
been tentatively called the Eta Lyrids. Again any shower members would
be slow if seen near the radiant and medium-fast if seen far from it.
Finally sporadic rates are nearing the nadir of their annual cycle as
seen from the Northern Hemisphere. I would expect to see 1-2 sporadic
meteors during the evening hours (with lunar interference) and perhaps
5-6 during the morning hours after the moon has set. Observers in the
Southern Hemisphere are luckier as they are approaching the zenith of
their annual sporadic curve. They may be able to see up to double the
activity listed above.
Clear Skies!
Robert Lunsford
AMS Visual Program Coordinator
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