Leonid Meteor Shower

This article was written with predictions for 2006, but apart from times and rates, this is still relevant every year. 

Dr. David Asher from the Armagh Observatory along with Dr. Rob McNaught have predicted an enhanced peak to occur on November 19th The Earth will pass very close to the centre of Tempel-Tuttle’s dust trail created at the comet’s 1932 return (i.e. 2 revolutions ago).

The calculated peak time of the outburst is 04:49 UT for the UK (Universal Time = Greenwich Mean Time). It will probably not last very long (i.e. meteor activity will rise and fall quite sharply) and so to see it you need to be in the right part of the world. The estimated Zenithal Hourly Rate, based on comparison with a similar event in 1969, is 120. Stargazers in Western Europe will have ringside seats: Leo will be high in the southeast sky, just before sunrise affording the very best Leonid views.

Apart from the encounter with the 1932 Leonid trail, there is a background to the Leonid shower for more than a week, at rather low rates (e.g. ZHR of 10 or so). The peak of the annual Leonids this year is 17th November 2300ut. Serious enthusiasts can observe for at least a few nights before and after the outburst, starting when Leo rises, in the middle of the night, until morning twilight.

Remember that the meteors radiate from the constellation of Leo outwards, so a long exposure could show meteors rising from the horizon! The showers are expected to last a few hours as the Earth passes through the comet trails. Observations after 0000UT will yield more sightings as the dark side of the Earth faces towards the incoming particle streams.

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!

Leonid Radiant