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:
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.
John W. Mason, Director, BAA Meteor Section
Saturn is at opposition on 15 April 2012 in the constellation of Virgo. With a magnitude of 0.2, it lies north east of Virgo’s brightest star, Spica (magnitude 0.98).
The north pole of the planet (and hence the north face of the rings) is iinclined by ~13.8 degrees towards the Earth. Small telescopes should be able to detect Cassini’s division in each ansae.
Small telescopes should also be able to detect what appears to be a single broad dark band in the planet’s northern hemisphere. This spans the latitudes of the classical North Equatorial and North Temperate belts.
Higher resolution observations reveal a lighter zone within this band at the approximate latitude of last year’s great northern hemisphere storm. Higher resolution observations have also detected some residual storm activity at this latitude.
A brighter bluish coloured zone is visible further north.
Recently on 12 April an image taken by Anthony Wesley showed a bright spot at an approximate latitude of 55 degrees N and an approximate System 3 longitude of 312 degrees. Further observations are required of this feature.
Mike Foulkes. Saturn Section director.