η-Aquariids(ETA): 19 Απρ. ως 28 Μαΐου Μέγ: 6 Μαΐου 2011

[Bi2L]

η-Aquariids (ETA)

πηγή imo.net

 

Active: April 19 – May 28; Maximum: May 6, 13h UT (λ⊙ = 45.5°);

ZHR = 70 (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 stream 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 places 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 most recent highest rates should have happened around 2008–2010, if this Jupiter-influenced cycle was borne-out, so ZHRs should be falling back from this peak in 2011, according to this idea.

 

Although activity in 2007 seemed unexpectedly weaker than normal (peak ZHRs maybe only ∼ 50), rates seemed to have been much better in 2008 and 2009 (ZHRs of ∼ 85 and 65 respectively). There seemed to have been no additional influence following the protracted, sometimes stronger than expected, Orionid returns from October 2006–2009 inclusive in the η–Aquariids in those years, as far as the available results allowed. New Moon on May 3 creates perfect viewing conditions for whatever the shower provides in 2011. All forms of observing can be used to study it, with radio work allowing activity to be followed even from many northern latitude sites throughout the daylight morning hours. The radiant culminates at about 08h local time.

[tolis45]

Βασίλη,

 

Αυτή η βροχή δίνει πάνω από 10 μετέωρα την ώρα τα πρωινά της

7ης, 8ης και 9ης Μαίου με μέγιστη δραστηριότητα κατά τις 0500 τοπική ώρα

αλλά:

 

Οι η Υδροχοίδες δεν δίνουν καθόλου δραστηριότητα πριν από τις 0300 τοπική,

δηλ αν κάποιος βγει έξω πχ τα μεσάνυχτα να παρατηρήσει, θα δει ένα μεγάλο κουλούρι

(τουλάχιστον από μεριάς Υδροχοίδων).

 

Τόλης.

[Bi2L]

Πολύ ωραία Τόλη, σε ευχαριστώ για την ενημέρωση.

 

Ας ελπίσουμε να μας κάνει καλό καιρο... γιατί μέχρι σήμερα μονο σύννεφα και τροχιές έχουμε.