Astronomical Society of Edinburgh
Journal 38

Meteor Notes

A combination of poor weather and unfavourable moonlight conditions has resulted in very few meteor observations in the Northern Network area during the first half of 1998. However, we can only hope that things will pick up over the coming months as the late summer and autumn showers arrive, for there are a number of potentially exciting events on the meteor front.

The August Perseids are one of the year's most reliable showers, and their recent enhanced activity has raised their popularity even further amongst amateur observers. The 'new' activity peak which began to appear in the late 1980s and early 90s occurred about twelve hours ahead of the 'traditional' maximum, and at its most intense produced zenithal hourly rates of up to 200 - considerably higher than the Perseids' typical peak of 80 to 100 meteors an hour. Since 1996, the enhanced activity - associated with the shower's parent comet, Swift-Tuttle, which last returned in 1992 - has become much less prominent, and will presumably soon fade back into the normal background of activity. In 1998, the shower maximum is predicted for the late evening of August 12th, so best rates should be seen overnight into the morning of the 13th. There will be a certain amount of interference from a waning gibbous moon, but dedicated observers should still be rewarded with a good number of meteors. As the Moon moves further into the morning sky over the succeeding nights, the declining activity of the shower may be followed under dark skies with watches in the first part of the night. [The night of 11/12 was cloudy, but Dave Gavine saw 26 Perseids and 5 sporadics in 2 hours on 12/13.]

September is often ignored by many meteor observers, yet reasonable rates may be had from the minor alpha Aurigid and Piscid showers, complemented by the rise of the background sporadic rate during the autumn months. A lot of attention, though, will certainly be directed skywards at the start of October, with the possibility of an outburst from the Giacobinids on the night of October 8th/9th. This shower doesn't usually rise much above the sporadic background level, but has produced spectacular short-lived storms when its parent comet, Giacobini-Zinner, makes one of its 6.6-year returns. The comet is at perihelion on November 21st, so 1998 could be one of those memorable years!

October's best-known shower, the Orionids, is composed of dust particles from Halley's Comet. It is particularly well-placed with respect to moonlight this year, with the October 21st maximum falling just one day after New Moon. Orion rises late in October, so this is one shower that gives best results if observed after midnight. From mid-October right through to until the end of November, there's also activity from the Taurids, which reaches a broad peak around November 3rd, and again around November 13th. Rates are never particularly high, but the slow-moving meteors are attractive to observe.

The highlight of the meteor observer's calendar this year will undoubtedly be November's Leonids. As is probably well-known by almost every amateur astronomer, this normally modest shower puts on a 'storm' of activity roughly every 33 years, when its parent Temple-Tuttle visits the inner solar system. The comet was at perihelion earlier this year, and the resulting enhanced activity is predicted for either 1998 or 1999. The Earth crosses the comet's orbit - and the path of the meteor particles - late on November 17th, 258 days after the comet itself passed that point. Predicting the actual time of any possible storm is difficult; observations of increased activity in recent years suggests it may occur over eastern Europe. However, the only way to guarantee catching the storm - if it happens - is to keep watch throughout this very important night! The famous outburst in 1966, which produced tens of thousands of meteors, lasted for only 40 minutes - don't expect to be able to glance out of your window at any time and see "meteors falling like snowflakes"! There's still a lot to find out about the distribution of dust around Temple-Tuttle, and its relationship with the meteor stream, so this is one shower that offers us no certainties.

The last major shower of the year, however, is one of the old reliables. The Geminids are active during the second week of December, with the 1998 maximum predicted for the early hours of December 14th. The Moon is well out of the way, being new on December 18th, so an overnight watch on the 13th/14th should be most productive. The high radiant and long hours of darkness combine to produce one of the finest meteor observing sessions of the year.

Brian Kelly Brian Kelly is Northem Coordinator for the BAA Meteor Section. He welcomes observations and correspondence, which should be addressed to him at 13 Rowanbank Gardens, Broughty Ferry, Dundee DD5 2JW. He can also be reached via e-mail at b.kelly@dundee.ac.uk