Leonid Meteors Outburst (2009) – Mark Stronge

This year’s annual display of the Leonid meteor shower occurs from 10th to 21st November, with the broad peak of activity occurring during Tuesday 17th and Wednesday 18th.

According to theoretical predictions by David Asher of the Armagh Observatory, and colleagues, there may be up to 100 meteors per hour seen under ideal conditions during the late evening of the 17th and early morning of the 18th November.

This year’s activity results mainly from the Earth passing through trails of dust emitted by Comet Tempel-Tuttle in the years 1466 and 1533. Esko Lyytinen and Markku Nissinen of Finland further predict that the 1466 trail may produce enhanced rates generally, with at least 40 meteors per hour occurring for much of November 17th.

Leonids travel at very high speeds through our atmosphere, at up to about 160,000 miles per hour, and many leave lasting glows known as persistent trains.

World-wide, conditions this year are favourable for observing the shower as there will be no interference from the nearly new Moon. The most favoured longitudes are from the extreme east of Europe to Japan. It is likely that viewers in the UK and Ireland will miss the main activity but might catch some long Earth-grazing meteors at the end of the display at around midnight on 17/18th November, after the radiant rises in the north-east at about 10:30pm. However, observers should, as usual, be on the alert for any unexpected meteor activity.

Weather permitting, observers should make themselves comfortable in a dark site away from artificial lights, and scan the area of sky from the north-west to east. At this time of year, you should of course wrap-up well in several layers of warm clothing to ward off the cold.

With thanks to the Armagh Observatory for the latest 2009 predictions and information.

General information

Every year roughly between November 15th and 19th, the Earth meets a stream of ancient debris, leading to the annual meteor shower visible in the early morning hours high in the northeast after midnight between those dates. The cometary dust particles move in very similar orbits and the resulting meteor shower appears to radiate from a point in the constellation Leo, hence the term Leonids.

The Leonids emanate from the trail of Comet Tempel-Tuttle which swings past the Sun approximately every 33 years, and during each close approach it emits a dense stream of dust and small particles. Over time, these dust trails extend along the whole length of the comet’s orbit, but the trails remain very narrow and concentrated in space taking hundreds of years to spread out. Comet Temple-Tuttle revolves around the Sun in the opposite direction to the Earth, so when the Earth encounters the trails of particles, they enter the atmosphere at very high speeds, about 160,000 mph. Most of the dust grains are very small, like grains of sand, and vaporise on entry in the first few seconds at heights of around 60 miles.

Those who wish to try for the Leonids are advised to find clear, dark site, wrap up well with several layers of warm clothing, a flask of tea/coffee/soup, and recline in a comfortable chair, or use something like a sleeping bag on top of a plastic ground sheet, and this way you won’t miss any. If other observers are there also, make sure they know just where you are in order to avoid accidents!