The Leonid Meteors 2002
The Leonids are the debris of Comet 55P/Tempel-Tuttle. Every 33 years or so, the comet returns to the inner solar system and releases material that forms into a new dust trail. In 2002 November the Earth will pass near the trails released at the 1866 and 1767 returns, i.e. 4 revolutions and 7 revolutions of the comet ago. The Earth's passage right through the centre of trails is associated with the most spectacular meteor displays (studies show that, as well as how close to the centre of the trail you are, the strength of the display also depends on how far along a trail's length you are).
The following diagram shows the close encounters of the Earth with Leonid dust trails in 2002 November.
Further explanation of this plot is available.
There will be two main peaks in the meteor activity, when the Earth runs through the centres of the 7-rev and 4-rev trails respectively. Estimates of the meteor activity, as normalised to a dark sky, are at meteor storm level. Unfortunately the moon will be full, making the sky brighter, so that the faintest meteors will not be visible. That is, the observational circumstances are not as good as in 2001 when the moon was not in the sky and observers at American and east Asian longitudes saw remarkable displays. Nevertheless, any meteor storm represents a rare opportunity, and if you have a clear sky, the 2002 Leonids should provide something memorable.
Meteor storms are generally shortlived events; sometimes the meteor rate is substantially reduced even just an hour from the time of maximum. At the critical time, you need to be on the part of the Earth's surface facing the direction that the meteors come from, and you need it to be night-time.
Which parts of the world will be best?
Below are Rob McNaught's visibility maps from the Astronomical Society of Australia web pages. The world is seen, from the direction of the Leonid radiant, in zenithal equidistant projection. The left is at night, the right is in daylight, and the bands in the middle represent astronomical, nautical and civil twilight. So you want to be at night; given that constraint, you see more meteors the nearer you are to the centre of the map, because Leo (where Leonid meteors appear to radiate from) will be higher in the sky. It is seen that the phase of the Moon is nearly full. The Moon is above the horizon everywhere to the left of the thick dashed line (the thinner dashed line corresponding to `lunar civil twilight').
The X towards the top is the north pole, and the Earth's rotation over several hours can be seen. You can view the background of the Leonid meteor shower at other times, basically between your own local midnight (exact time being latitude dependent) and morning twilight; it's just that you'll miss the encounters of the Earth with meteors from these particular dust trails if you're not in the parts of the world on these maps.
The above two maps show the regions of visibility at the times (uncertainties a few minutes) when the Earth encounters the 7-rev and 4-rev trails respectively. Note that the dates and times are in UNIVERSAL TIME (Greenwich Mean Time).
The maps show that to experience the first maximum, you want to be in western Europe or western Africa (alternatively some eastern parts of the Americas, although the Leonid radiant will be lower in the sky); and for the second peak in North America.
Depending on the duration of the dust trail encounters, significant meteor activity could be visible marginally outside the regions shown. The duration (Full Width Half Maximum) is estimated as 130 minutes for the first encounter (7-rev trail) and about 70 min for the second (4-rev). There will be a dip in activity between the two main peaks, which are several hours apart. Estimated profiles have been plotted by Bill Cooke.
Meteors resulting from the Earth's passage through outer regions of the 1965 (1-rev) trail, and meteors in the `traditional' Leonid peak associated with the orbital plane of the comet (the point where the comet passed through the ecliptic in 1998 is shown by a green X in the above diagram), will, if they are visible at all, occur in the later hours of November 17th Universal Time. This corresponds to Asian longitudes in the early hours of the 18th local time, a day before the two main peaks.
If you are keen (aren't we all), then wherever you are in the world it is worth observing from when Leo rises, in the middle of the night, until morning twilight, for a couple of nights around the maximum. If you are using the full moon as an excuse for not being keen, then the above maps show the parts of the world most favoured this year.
Last Revised: 2002 November 8th
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