The Leonid Meteors 2001:
a chance to see a meteor storm

Reports of 2000 Observations from the IMO

Reports of 2000 Observations from the AMS

Reports of 2000 Observations from ESA

Radio Meteor Forward Scatter Observations

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 2001 November the Earth will pass near the trails released at the 1866, 1767 and 1699 returns, i.e. 4 revolutions, 7 revolutions and 9 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 2001 November.

Further explanation of this plot is available.

In 2002 the Earth also encounters trails very closely. Estimates of the meteor activity, as normalised to a dark sky, are as good in 2002 as 2001, perhaps even better, but the full moon in 2002 means that 2001 is favoured observationally.

Therefore the 2001 Leonids represent a rare meteor observing opportunity. But meteor storms are generally shortlived events; in many cases 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. The phase of the Moon (just after new) is drawn as seen from the southern hemisphere. This year, the Moon will have set while Leonids are visible (in the maps, the Moon is above the horizon only above the dashed lines very near the top of the maps).

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 three maps show the regions of visibility at the times (uncertainties a few minutes, durations of the order of an hour) when the Earth encounters the 7-rev, 9-rev and 4-rev trails respectively. Note that the dates and times are in UNIVERSAL TIME (Greenwich Mean Time).

The maps show that you want to be at East Asian longitudes or in North America to experience the meteor display from one or other dust trail encounter.

East Asia or North America?

Various astronomers (e.g. see the Leonid MAC page) have independently derived results suggesting that North America and East Asia / Australia will see major Leonid outbursts in 2001. There are differences in the precise details derived: e.g., is N America or E Asia better, and what are the relative observable meteor rates of the two? According to the ZHR (Zenithal Hourly Rate of meteors) model of McNaught and Asher, the display in N America is a likely meteor storm, and in E Asia is a guaranteed meteor storm. For the latter, the above maps show peak meteor rates to occur at 17:31 and 18:19 UT, but the reality is that meteor storms from different dust trail encounters will overlap in time (in fact, smaller contributions from the 10-rev and 11-rev trails will also be added to the meteor rate profiles from the 9-rev and 4-rev trails). It should be worth observing from when Leo rises, in the middle of the night, until morning twilight (this is also true if you are observing from N America). High meteor activity will continue a little while after 18:19, and so if you are too far to the east, you will already be in twilight before the meteor storm ends.

Go to Armagh Observatory Leonid page.

Last Revised: 2001 August 16th WWW contact: webmaster@star.arm.ac.uk

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