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Leonids 2000 Special Report

Between midnight and dawn of the night of November 17 to 18, provided skies are clear, a "meteor shower" called the Leonid shower will occur.

It will be visible from (mainly western) Europe and Africa, as well as from large parts of North America, Central America and parts of South America.

When it peaks

A first peak, visible from western Europe and Africa (including central Europe) and NE South America, is expected around 3:44 a.m. Greenwich Mean Time, which is 4:44 a.m. local time for most of the favored continental European and African locations, 3:44 a.m. for the British Isles, mainland Portugal, and the Canary Islands, and 1.44 a.m. for eastern Brazil.

A second peak, visible from large parts of North America, Central America, and NW South America, is expected around 7:51 a.m. Greenwich Mean Time, which is 3:51 a.m. Atlantic Standard Time, 2:51 a.m. Eastern Standard time, 1:51 Central Standard Time, and 0:51 a.m. Mountain Standard Time.

This peak falls too early for Pacific Time Zone locations, unfortunately. At the times mentioned above, an observer at the indicated locations may expect to see 50 to 100 meteors per hour.

How many meteors?

A veritable meteor storm with several tens of meteors per minute as last year is much less likely this year, but not ruled out.

The Leonids are caused by a stream of predominantly very small particles, less than 1 mm in size, which orbit the Sun with a period of 33 years, together with their parent comet, Tempel-Tuttle.

The orbit of the Leonid particles happens to intersect the Earth's orbit.

Each year around November 17, when the Earth is at this intersection, Leonid particles may enter the Earth's atmosphere and cause meteors, popularly called "shooting stars."

This year, around 3:44 a.m. Greenwich Mean Time, in the morning hours of the night of November 17 to 18, the Earth will pass through the outer regions of a reasonably dense dust trail of Leonid particles ejected by Comet Tempel-Tuttle 8 orbital revolutions (267 years) ago.

Around 7:51 a.m. Greenwich Mean Time, the Earth will pass through the outer regions of another dust trail, ejected 4 orbital revolutions (134 years) ago. Results on past encounters of the Earth with these particular dust trails are scarce, making it hard to predict the level of activity.

The tentative frequency of around 100 meteors per hour is our best guess, but the real activity may be both higher or lower. Leonid meteor storms are probable in 2001 and 2002, too.

Actually, Leonid meteors can be seen every year around November 17. Along the larger part of Comet Tempel-Tuttle's orbit, however, Leonid particles are scattered sparsely, so that, in most years, we see only a few Leonid meteors per hour. Only in the vicinity of the Comet, the density of Leonid particles is much higher.

Therefore, we observe much higher Leonid activity every 33 years during a couple of years, when Comet Tempel-Tuttle revisits our region of the Solar System.

Leonids in history

In some instances, we even see a real meteor storm. Old chronicles contain references to past Leonid meteor storms back to the 10th century A.D. The best-known Leonid meteor storms are those of 1833 and 1966, when tens of meteors per second darted across the skies during the peak hour.

The 1833 meteor storm was so spectacular that it in fact launched meteor research as a branch of astronomy.

Since the 1966 meteor storm, Comet Tempel-Tuttle has completed another revolution around the Sun. The passage of the Comet through its closest point to the Sun on February 28, 1998 marked the beginning of a five-year period (1998-2002) during which strongly increased Leonid meteor activity is again possible.

Although 1998 gave us an unexpected (but meanwhile convincingly explained) fireball shower, the first storm in the present Leonid epoch occurred last year, with a peak activity around 60 meteors per minute (yielding an equivalent hourly rate of 3700).

Both peak time and actual activity matched the predictions by astronomers David Asher and Robert McNaught very well, so that there is good hope that the predictions for the period 2000-2002 are reliable, too.