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Wednesday, 25 April 2012


BAA electronic bulletin

The annual Lyrid meteor shower peaks this weekend on the night of April
21-22 when Earth passes through a stream of debris from Comet C/1861G1
Thatcher. The incoming Lyrid meteoroids have atmospheric entry velocities of
49 km/s, and Lyrid meteors appear swift. A fair proportion are bright, and
some leave persistent ionisation trains.

The April Lyrid shower, while relatively modest, brings a welcome upturn in
rates for a few nights, particularly around the maximum - this year expected
just before dawn on Sunday, April 22 - normally producing observed rates of
perhaps 6-8 meteors/hr under the clearest and darkest conditions when the
radiant is well up in the sky, corresponding to a corrected Zenithal Hourly
Rate (ZHR) around 10. Activity is about this level for 12 hours or so
centred on the maximum. At other times, observed Lyrid rates may be only 2-3

The best observed Lyrid rates will typically be found after midnight, when
the radiant (RA 18h 08m Dec +32°) located some 10 degrees south-west
of Vega, near the Lyra/Hercules border, climbs higher in the sky. The
radiant elevation approaches a very respectable 66 degrees by 0300 hrs local

This year's peak coincides with a new Moon, so there will be absolutely no
interference by moonlight.  The promise of a good Lyrid display has prompted
NASA to plan an unusual 3D meteor photography experiment combining
observations from the ground, a research balloon, and the International
Space Station.  More details are available on:

Although Lyrid activity is generally rather modest, unmapped filaments of
dust laid down by the comet occasionally trigger outbursts in rates - most
recently in 1982 when, for a couple of hours, a ZHR around 200 was attained.
While there is no expectation of enhanced activity in 2012, the Lyrids have
sprung surprises on us in the past, and remain a shower very much worth

This e-bulletin issued by:
John W. Mason, Director, BAA Meteor Section
2012 April 20

BAA-ebulletin mailing list or visit:
(c) 2012 British Astronomical Association
Good Clear Skies
Colin James Watling
Various Voluntary work-Litter Picking for Parish Council (Daytime) and also a friend of Kessingland Beach (Watchman)
Real Astronomer and head of the Comet section for LYRA (Lowestoft and Great Yarmouth Regional Astronomers) also head of K.A.G (Kessingland Astronomy Group) and Navigator (Astrogator) of the Stars (Fieldwork)
Information -- And More Info

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