[meteorite-list] The 2003 Leonid Meteor Shower

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:25 2004
Message-ID: <200310102154.OAA25459_at_zagami.jpl.nasa.gov>

http://science.nasa.gov/headlines/y2003/10oct_doubleleonids.htm

The 2003 Leonid Meteor Shower
NASA Science News
October 10, 2003

An unusual double Leonid meteor shower is going to peak next
onth over parts of Asia and North America.

The Leonid meteor shower is coming. Twice.

Bill Cooke of the Space Environments Group at the NASA Marshall Space
Flight Center explains: "Normally there's just one Leonid meteor shower
each year, but this year we're going to have two: one on Nov. 13th and
another on Nov. 19th."

Both are caused by comet Tempel-Tuttle, which swings through the inner
solar system every 33 years. With each visit the comet leaves behind a
trail of dusty debris--the stuff of meteor showers. Lots of the comet's
old dusty trails litter the mid-November part of Earth's orbit.

"Our planet glides through the debris zone every
year," says Cooke. "It's like a minefield.
Sometimes we hit a dust trail, sometimes we don't."
Direct hits can spark a meteor storm, which is
defined as more than 1000 shooting stars per hour.
"That's what happened in, for example, 1966 and
2001," says Cooke. "Those were great years for
Leonids."

"This year we're going to brush past two of the trails--no direct hits,"
he says. Even so, "we might have a nice display."

The first shower is expected on Nov. 13th around 17:17 UT. For about
three hours centered on that time Earth will be close to some dust shed
by Tempel-Tuttle in the year 1499. Sky watchers in Alaska, Hawaii and
along the Pacific rim of Asia are favored. They'll see anywhere from a
few to 40 meteors per hour--"if they can avoid the glare from that
night's gibbous Moon," cautions Cooke. A good strategy for moonlit meteor
observing: travel to high altitudes where the air is clear or stand in
the shade of a tall building or hillside.

        Leonid meteor rates for selected cities: Nov. 13-14, 2003

       City Local Time Maximum number of
                                                 Leonids in 15 min.

       Los Angeles, CA 5:15 a.m. (Nov. < 3
                                   13th)

       Seattle, WA 5:45 a.m. (Nov. 3
                                   13th)

       Fairbanks, AK 7:00 a.m. (Nov. 10
                                   13th)

       Honolulu, HI 5:30 a.m. (Nov. 9
                                   13th)

       Tahiti 5:00 a.m. (Nov. 6
                                   13th)

       Tokyo, Japan 2:30 a.m. (Nov. 18
                                   14th)
       Christchurch, New 3:30 a.m. (Nov.
      Zealand 14th) 1

       Sydney, Australia 3:30 a.m. (Nov. 9
                                   14th)

       Hong Kong 2:00 a.m. (Nov. 8
                                   14th)

       Beijing, China 1:45 a.m. (Nov. 10
                                   14th)
       Manila, the 1:45 a.m. (Nov.
      Philippines 14th) 9

Table notes: Values listed in the 3rd column are the maximum number of
meteors an observer with perfectly clear dark skies might see in a
15-min. interval.

Curiously the Moon will be much closer to the 1499 trail than Earth will
be. "If the Moon had an atmosphere to catch the comet dust, there would
be about 1400 meteors per hour in lunar skies--a real storm," notes
Cooke. Instead, the Leonids will simply hit the ground.

Most Leonid meteoroids are microscopic, and when they hit the Moon they
do little more than raise a puff of moon dust. But a few will be bigger:
the size of golf balls or grapefruits. Traveling about 160,000 mph, these
impactors can cause explosions visible from Earth. (For more information
about this, read the Science_at_NASA story Explosions on the Moon.)

"This year we won't be able to see any lunar impacts," notes Cooke,
"because most of the Leonids will strike the far side of the Moon. Some
will hit the Earth-facing side, but the ground where they hit will be
sunlit. That makes it very hard to see the explosions."

The second and more impressive shower arrives almost a week later on Nov.
19th when Earth approaches a trail shed in 1533. "Sky watchers up and
down the US east coast will have the best view," says Cooke. "For a while
around 07:28 UT (2:28 a.m. EST), they could see more than one meteor per
minute." The Moon, a thin crescent on Nov. 19th, won't be bright enough
to interfere with the display. (Nor will it be close to the cometary dust
stream, so once again there will be no visible lunar explosions.)

          Leonid meteor rates for selected cities: Nov. 19, 2003

       City Local Time Maximum number of
                                                 Leonids in 15 min.

       New York, NY 2:30 a.m. (Nov. 17
                                   19th)

       Miami, FL 2:30 a.m. (Nov. 14
                                   19th)

       Chicago, IL 1:30 a.m. (Nov. 13
                                   19th)

       Dallas, TX 1:45 a.m. (Nov. 9
                                   19th)

       Denver, CO 0:45 a.m. (Nov. 7
                                   19th)

       Los Angeles, CA 0:00 a.m. (Nov. 3
                                   19th)

       Caracas, Venezuela 3:30 a.m. (Nov. 17
                                   19th)
       San Juan, Puerto 3:30 a.m. (Nov.
      Rico 19th) 18

       Bermuda 3:30 a.m. (Nov. 19
                                   19th)

       London, England 5:45 a.m. (Nov. 7
                                   19th)

       Paris, France 6:30 a.m. (Nov. 6
                                   19th)

Cooke assembled these forecasts using data from several researchers who
have done a good job predicting Leonid storms in recent years: Peter
Jenniskens at NASA's Ames Research Center, Jeremy Vaubaillon of the
Institut de Mecanique Celeste et de Calcul des Ephemerides in France, and
Esko Lyytinen. They mostly agree that Earth will encounter dust streams
on Nov. 13th and 19th, but there is less consensus about how intense the
resulting showers will be. Lyytinen, for instance, predicts a maximum of
just 30 meteors per hour on Nov. 19th. Vaubaillon says 100.

Who's right? See for yourself. Be outside when the time comes, looking
up.
Received on Fri 10 Oct 2003 05:54:18 PM PDT