Pons-Winneckid meteors 2004 - Active June 26-July 2

[Rick]

BAA electronic circular No. 00154  http://www.britastro.org/

Observing Opportunity - Pons-Winneckid meteors 2004
Active June 26-July 2
Radiant RA 14h 56m Dec +47o

Produced by debris from the short-period comet 7P/Pons-Winnecke, this shower has an interesting observational history. Substantial displays were seen in 1916, 1921 and 1927 associated with then-recent perihelion returns of the parent comet. Subsequent gravitational perturbations by Jupiter pulled the comet orbit outwards from that of the Earth by a large and, from the point of view of producing meteor activity, unfavourable 0.24 astronomical units. It therefore came as something of a surprise when a significant display of Pons-Winneckid meteors occurred on 1998 June 27-28, with observed rates up to 60 meteors/hr over a roughly 12-hour period extending to about June 28d 03h UT. Later calculations by Asher and Emil'yanenko suggested that the outburst was produced by debris released from the parent comet at its 1825 perihelion, remaining in a 2:1 orbital/gravitational resonance with Jupiter. It is considered likely that we shall again encounter this material in 2004, bringing the possibility of a significant display peaking around 01h UT on the Saturday night to Sunday morning of June 26-27.

Pons-Winneckid meteors emanate from a radiant in northern Bootes (some European observers refer to the shower as the 'June Bootids'). The meteors are very slow, with geocentric velocity 14 km/sec. A characteristic of showers with such slow meteors - October's periodic Giacobinids are another example - is that the radiant is rather diffuse and poorly defined. Observations in 1998 showed most Pons-Winneckid meteors to be in the medium-to-faint magnitude rage; bright events were comparatively scarce.

Little if any Pons-Winneckid activity has been reported in the years since 1998: alerted by that year's unexpected return, observers have been on careful lookout! Certainly, nothing out of the ordinary happened in 2003: (The parent comet was back at perihelion in May 2002, but the material responsible for the outbursts is long-separated from it, and there is no reason to correlate high meteor activity with the comet's current movements).

The possible 2004 return will be accompanied by a waxing gibbous Moon (9 days old), low to the southwest around midnight UT. This shouldn't interfere too badly with observations, given that for UK observers the night sky at this time of year is essentially twilit in any case. Watches should be made by standard methods (outlined on the Meteor Section web pages at http://www.britastro.org/meteor ); in the unlikely event of rates becoming higher than 5 meteors/minute, observers should concentrate on making counts, rather than recording magnitude, time and train data for individual meteors. The short summer night will restrict watches to only a couple of hours' duration, but it is still important that observers at least try to follow what activity, if any, is produced by the Pons-Winneckids this year - remember that negative reports are also of value, and should be submitted to the Meteor Section!

Despite the success of new models in forecasting the occurrence and timing of recent Leonid storms, there is no absolute guarantee that the forecast Pons-Winneckid activity will manifest in 2004 - actual naked eye, visual observations are essential to find out what's really going on.

Observations will, as always, be welcomed by the Meteor Section Director.

Neil Bone.

[ This Message was edited by: Rick on 2004-06-25 08:28 ]