[BAA-ebulletin 00667] LYRID METEOR SHOWER NEARS PEAK

[BAA electronic bulletins service]

LYRID METEOR SHOWER NEARS PEAK

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
meteors/hr.

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
time.

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:
 http://science.nasa.gov/science-news/science-at-nasa/2012/18apr_lyrids/

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
observing.


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