Most everyone has glimpsed an occasional “shooting star,” or meteor. But
imagine what it would be like to see hundreds — or even thousands — of
them in a single night. Such a spectacle may occur in the hours before
dawn on Sunday, November 18th. In fact, if astronomers’ predictions hold
up, skywatchers in North America can expect to see their most dramatic
meteor display in 35 years. “Earth is about to plow through a cloud of
space dust that could light up our skies with celestial fireworks,” notes
Alan MacRobert, senior editor for SKY & TELESCOPE magazine.

These meteors, called Leonids because they appear to radiate from the
constellation Leo (the Lion), will signal the arrival of fast-moving dust
particles shed by Comet Tempel-Tuttle, which loops around the Sun every
33 years. Like a truck on a dirt road, the comet creates a dusty wake
that spreads along its orbit. When Earth crosses that orbit in mid-
November each year, skywatchers usually see a handful of shooting stars,
a weak meteor “shower.” But three times each century Earth crosses the
dust stream where it’s especially dense, and when that happens we
experience what astronomers call a meteor “storm.”

Meteors are created when sand- or pebble-size grains strike Earth’s
atmosphere at high speed and create streaks of superheated air along
their paths. The Leonids, which are one of a dozen or so annual meteor
showers caused by streams of cometary debris, arrive at a blistering
44 miles (71 kilometers) per second — the fastest known. Two years ago
the Leonids briefly peppered the skies over Europe and the Middle East
with 3,000 meteors per hour (nearly one every second). In 1966 lucky
observers in the southwestern United States gaped in awe for 20 minutes
as Leonid meteors fell at the rate of 40 per second!

In the November 2001 issue of SKY & TELESCOPE, meteorologist Joe Rao
assesses the predictions provided by three teams of specialists, who
agree that two dramatic storms appear likely this month.

A burst lasting perhaps two hours is expected in the predawn hours of
November 18th for observers throughout most of North and Central America.
The maximum rates should occur near 5:00 a.m. EST (corresponding to
4:00 a.m. CST, 3:00 a.m. MST, 2:00 a.m. PST). With no moonlight spoiling
the view, the storm may briefly spawn anywhere from several hundred to
1,000 or 2,000 meteors per hour for observers with clear, very dark
skies. A fourth prediction, issued recently by NASA researcher Peter
Jenniskens, argues that the hourly rate could top 4,000.

An even bigger storm is expected 8 hours later for viewers rimming the
far-western Pacific Ocean. Because these locations lie on the other side
of the International Date Line, this peak occurs before dawn on November
19th. Several thousand meteors may streak across the sky for an hour or
so starting about 3:00 or 4:00 a.m. in eastern Australia (depending on
location); 2:00 a.m. in Japan; and 1:00 a.m. in western Australia, the
Philippines, and eastern China.

“If Earth manages to pass through a thick concentration of material,”
Rao notes, “the upper atmosphere can blaze with meteors storming like a
fiery rain from the Sickle of Leo.”

THE PUNDITS’ PREDICTIONS

Peak Activity in North America (morning of November 18th) 

                     Hourly Rate     Midpoint time     Midpoint time
                                         (EST)             (PST)

Asher & McNaught           800          4:55 a.m.         1:55 a.m.
Brown & Cooke             1300          8:00 a.m.         5:00 a.m.
Lyytinen & Van Flandern   2000          5:28 a.m.         2:28 a.m.
Jenniskens                4200          5:09 a.m.         2:09 a.m.

(These meteors will be dominated by dust particles shed by Comet Tempel-
Tuttle in 1767, though Brown & Cooke believe the dominant source will be
dust shed in 1799.)

Peak Activity in Asia and Australia (morning of November 19th) 

                     Hourly Rate     Midpoint time     Midpoint time
                                        (Toyko)          (Sydney)

Asher & McNaught          2000         2:24 a.m.         4:24 a.m.
                          8000         3:13 a.m.         5:13 a.m.
Brown & Cooke              800         2:00 a.m.         4:00 a.m.
Lyytinen & Van Flandern   8500         3:15 a.m.         5:15 a.m.
Jenniskens                1800         2:08 a.m.         4:08 a.m.
                          2700         2:55 a.m.         4:55 a.m.

(These meteors, which may arrive in two distinct bursts, will be dominated
by particles shed by Comet Tempel-Tuttle in 1699 and 1866, respectively)

IMAGE CAPTION:
[http://www.skypub.com/news/images2001/pr_leonids2001_leonidglobes_big.jpg (276KB)]

Left: This “meteor’s-eye view” shows how Earth will be oriented for the
first expected peak of the Leonid shower on November 18, 2001, at about
5 a.m Eastern time. This is when the various experts predict that Earth
will encounter particles released by Comet Tempel-Tuttle in 1766. While
this entire hemisphere will experience the shower, meteors will only be
visible in the nighttime region to the left. Right: About 8 hours later,
a second and perhaps stronger burst of meteors is expected over the
Pacific Ocean, favoring observers in Australia and eastern Asia. Sky &
Telescope diagram.