THE MAGIC OF MIGRATION

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The Greatest Show on Earth

The sight of a lifetime may be coming to a sky near you on the night of November 17-18. We're talking about a spectacle that might truly deserve the epithet "of biblical proportions," a "meteor storm" featuring possibly thousands of meteors per hour. If it occurs, which is by no means a certainty, what is the best way to catch this phenomenal natural event? To answer that question, we first need to discuss a little background about meteors in general and the Leonid shower and storm in particular.

Meteors, popularly known as falling stars or shooting stars, are actually streaks of light caused when bits of space rock or iron enter Earth's atmosphere at tremendous speeds and burn up from friction. Many meteors are debris from comets. And when Earth passes near the orbits of certain comets on the same days each year, what we see is an increased number of meteors seeming to shoot out from a particular point in the constellations-in other words, a "meteor shower."

Now suppose that the pieces of space dust and rock are not scattered evenly around the orbit of a comet. Suppose there is a tremendously denser "meteoroid swarm," perhaps following the comet itself around its orbit. When this is the case, there will come, once in many years or decades, a time when the Earth passes into the swarm and we get to see not just an ordinary meteor shower, not just five or ten or even 50 meteors per hour. If the swarm is dense enough, it may produce in our skies hundreds, or even thousands of meteors per hour—a meteor storm.

The greatest meteor storms known in history are those that have been produced by Comet Tempel-Tuttle and the Leonid meteor shower. The comet takes an average of about 33 years to complete one orbit, so about every 33 years there is a chance—usually in the year or two after the comet passes Earth and sun—that we will enter the Leonid swarm and see a storm of these shooting stars pour out of Leo the Lion on a single incredible morning in mid-November.

There are just two problems. Sometimes the big year comes and the storm doesn't happen. The gravity of the planet Jupiter tends to cause small but significant changes in the comet's orbit, and with it, the swarm. The storm was magnificent in 1799. Then on November 13, 1833 it was even greater: That was "The Night the Stars Fell on Alabama," while farther north, the flashes of thousands of Leonid meteors awakened Bostonians in their beds. In 1866 there was a lesser but still impressive Leonid display. But around 1899—1900 and 1933, the showing was far less spectacular. What would happen in 1966?

What happened before dawn on November 17, 1966, was the greatest meteor storm on record. In Arizona a team of astronomers watched in awe as the numbers kept increasing. At each moment, there were numerous meteors bursting, numerous meteors brighter than any star, and numerous lingering trails. The astronomers estimated that the rate peaked at about 500,000 per hour!

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