η-Aquariids (ETA)-19 Απριλίου-28 Μαϊου (Μεγιστο 6 Μαϊου)

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πηγη imo.net

η-Aquariids (ETA)

http://www.imo.net/calendar/2009#aprjun

Active: April 19-May 28

Maximum: May 6 0h UT (λo = 45°5

ZHR = 85 (periodically variable - ~ 40-85)

Radiant: α = 338° δ = -01°

Radiant drift: see Table 6

v∞ = 66 km/s; r = 2.4

TFC: α = 319° δ = +10° and α = 321° δ = -23° (β < 20° S)

 

A fine, rich shower associated with Comet 1P/Halley, like the Orionids of October, but one visible for only a few hours before dawn, essentially from tropical and southern hemisphere sites. Some useful results have come even from sites around 40°N latitude in recent years however, and occasional meteors have been reported from further north, but the shower would benefit from increased observer activity generally. The fast and often bright meteors make the wait for radiant-rise worthwhile, and many events leave glowing persistent trains after them. While the radiant is still low, η-Aquariids tend to have very long paths, which can mean observers underestimate the angular speeds of the meteors, so extra care is needed when making such reports.

 

A relatively broad maximum, sometimes with a variable number of submaxima, usually occurs in early May. Fresh IMO analyses in recent years, based on data collected between 1984-2001, have shown that ZHRs are generally above 30 between about May 3-10, and that the peak rates appear to be variable on a roughly 12-year timescale. The next highest rates should fall towards 2008-2010, if this Jupiter-influenced cycle is borne-out, thus ZHRs could be around their very best in 2009, according to this idea. However, activity in 2007 seemed unexpectedly weaker than normal (peak ZHRs maybe only ~ 50), which combined with the unexpectedly strong Orionid returns in October 2006 and 2007, add an extra degree of uncertainty over what may happen from the η-Aquariids this year. The waxing gibbous Moon on May 6 will set in time to still leave most of the best-visible interval viable for visual watchers well south of the equator, at least. All forms of observing can be used to study the shower, with radio work allowing activity to be followed even from many northern latitude sites throughout the daylight morning hours. The radiant culminates at about 8h local time.

http://www.imo.net/calendar/2009#aprjun

 

H φωτογραφια ειναι απο τους

η-Aquariids (ETA) 2008

ΟΧΙ 2009