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(meteorobs) Excerpts from "CCNet 116/2000 - 10 November 2000"
------- Forwarded Message
From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet, 10 November 2000
Date: Fri, 10 Nov 2000 13:17:04 -0000
CCNet 116/2000 - 10 November 2000
---------------------------------
(1) THE LEONIDS ARE COMING: EXPECTATIONS FOR LEONIDS METEOR ACTIVITY
Marc Gyssens <marc.gyssens@luc.acdot be>
(2) LEONID METEOR BALLOON RISES AGAIN
NASA Science News <snglist@lyris.msfc.nasadot gov>
(3) U.S. EAST COAST MAY OFFER BEST VIEW OF LEONIDS METEOR SHOWER
Ron Baalke <baalke@jpl.nasadot gov>
[...]
======================================================================
(1) THE LEONIDS ARE COMING: EXPECTATIONS FOR LEONIDS METEOR ACTIVITY
>From Marc Gyssens <marc.gyssens@luc.acdot be>
I N T E R N A T I O N A L M E T E O R O R G A N I Z A T I O N
Press release
Night of November 17-18: expectations for Leonid meteor activity
================================================================
From, mainly western, Europe and Africa, as well as from large parts of
North America, Central America and parts of South America, people may see a
lot of meteors - "shooting stars" - between midnight and dawn of the night
of November 17 to 18, provided skies are clear. These meteors belong to the
so-called Leonid shower.
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. A veritable meteor storm with
several tens of meteors per minute as last year is much less likely this
year, but not ruled out. Therefore, vigilance is called for!
The International Meteor Organization, who collects meteor observations
world-wide for the purpose of analysis, wishes to point the attention of the
public to this spectacular natural phenomenon.
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! Should Leonid meteor activity not
rise above expectations in 2000, it is good to know that 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. 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.
In order to see meteors, the sky must be clear and the selected observing
site should preferentially be free of light pollution; the less light, the
more meteors will be seen! Notice that Leonid meteors cannot be seen before
around midnight. Hence, there is no point in starting an observation
earlier. Die-hards who do not want to miss anything of the show should then
continue to watch until dawn. People who cannot afford to stay up that long
should focus on a period of 1 to 2 hours centered around the predicted peak
time for their region.
Mind that it can be very cold in mid-November: warm clothing adapted to the
local climate is essential! For comfortable observing, use a reclining
chair, and install yourself in a suitable sleeping bag or under several
blankets. While observing, do not fix a particular star, but look relaxedly
and patiently to a wide area of sky and wait for shooting stars to appear.
- ------------------------------------------------------------------------
More information on the Leonids can be found in the International Meteor
Organization's bimonthly journal WGN and on the internet, at
http://www.imodot net and http://www.amsmeteors.org/imo-mirror.
For questions, contact Marc Gyssens at wgn@imodot net or +32-477-64 05 48.
Notice that the International Meteor Organization will send out a new
release with first results on the Leonids during the European early morning
hours of November 18, immediately after the event. All recipients of the
present release will automatically receive the new release.
======================================================================
(2) LEONID METEOR BALLOON RISES AGAIN
>From NASA Science News <snglist@lyris.msfc.nasadot gov>
http://science.nasadot gov/headlines/y2000/ast09nov_1.htm?list20392
NASA Science News for November 9, 2000
November 9, 2000: On Nov. 17 and 18, 2000, space forecasters expect a series
of Leonid meteor outbursts with flurries possibly exceeding 100 shooting
stars per hour. Observers in Europe, Africa, and the eastern half of the
United States and Canada are generally favored for best viewing, but the
Leonids are notoriously unpredictable. Everyone, everywhere should remain
alert for meteors during the hours before local dawn next Friday and
Saturday. [Observing tips!]
Meteor watching under a crisp November sky with twinkling stars and bright
planets is an experience that's hard to beat -- even at 3 in the morning!
But if clouds, rain, or city lights threaten to spoil your pre-dawn
stargazing adventure, NASA scientists are prepared to help.
Before dawn on Saturday, Nov. 18th, a team of astronomers and ham radio
amateurs at NASA's Marshall Space Flight Center (MSFC) plan to launch a
specially-equipped weather balloon to monitor the Leonid meteor shower
100,000 feet above Earth's surface, far from obscuring clouds and urban
light pollution. Video from the flight will be broadcast live on the web at
LeonidsLive.com and replays will be available less than 24 hours later.
This will be the third annual Science@NASA-sponsored broadcast of the
Leonids from the stratosphere. In 1998 and 1999 more than two million people
watched live webcasts during the meteor shower or saw replays the morning
after.
This year's liftoff is scheduled for 0630 Greenwich Mean Time (0030 CST) on
Saturday, Nov. 18th, from the Marshall Space Flight Center's Atmospheric
Research Facility (ARF). The balloon will carry a sensitive low-light CCD
video camera to monitor the shower from an altitude of about 32 km (100,000
ft).
"Earth is going to pass through the outskirts of three meteoroid debris
streams from comet Tempel-Tuttle on Nov. 17th and 18th," says Marshall
astronomer Mitzi Adams. "The last of the three stream encounters will take
place at approximately 0800 GMT on Nov. 18th, just as the meteor balloon is
reaching its maximum altitude. The timing couldn't be better."
"The balloon will carry a sensitive CCD camera to record the meteors," added
Ed Myszka, an engineer and radio amateur who built the balloon payload. "The
field of view will be about 20 degrees. That's about twice the size of the
bowl of the Big Dipper.
"We plan to downlink the video to our ground station at the ARF as an
amateur TV signal at 426.25 MHz -- that's Cable Ready TV Channel 58. The
transmission should be detectable for several hundred miles around the
launch site. Hams in the vicinity of north Alabama and Tennessee will be
able to monitor the flight themselves. And of course the video stream will
be available for everyone on the web at LeonidsLive.com."
Sound effects during this year's flight will be provided by an INSPIRE VLF
radio receiver, which is sensitive to radio emissions below 10 kHz. The very
low frequency (VLF) radio band is filled with exotic-sounding signals called
spherics, tweeks and whistlers. All three are impulsive bursts caused by
distant lighting. "Spherics," which are caused by lightning strokes within a
couple of thousand kilometers of the receiver, sound like twigs snapping or
bacon sizzling on a grill. Tweeks and whistlers are caused by more distant
lightning, and sound like brief descending musical tones.
Dennis Gallagher, a plasma physicist at the Marshall Space Flight Center,
thinks that the VLF receiver might also pick up natural radio emissions from
the Leonid meteors.
"Meteoroids produce an ionized trail as they plow through the atmosphere,"
explained Gallagher. "There's a low density wake right behind the meteoroid.
Because electrons are more mobile than protons, they move in to fill the
void faster. That could set up plasma oscillations and trigger radio
emissions."
The VLF receiver was donated to the Marshall Space Flight Center for this
and future flights by the Goddard INSPIRE program. It's been christened the
"Marina receiver" after the daughter of Flavio Gori, an Italian scientist
who first suggested flying the receiver.
Gallagher and his colleagues also plan to operate another VLF receiver at
the launch site to provide a ground reference for comparison with data
collected from the stratosphere. During the flight, signals from the
receiver will be converted to audio sounds and transmitted along with images
from the CCD video camera. Web viewers at LeonidsLive.com will be treated to
an unusual combination of meteoritic sights and sounds.
The question of radio emissions from meteors is an intriguing one, says
Gallagher, and you don't need to send your receiver to the stratosphere to
listen in. Anyone with a VLF receiver can monitor the Leonids on November 18
and Gallagher hopes that INSPIRE participants across the USA will join in
the effort. The best way to collect data is to record the output of the
receiver on a two-track audio recorder. Record the VLF signal on one track
and a WWV time signal on the other. This way VLF pulses can be correlated
with the times of bright meteors seen from your observing site. It's also a
good idea to conduct at least one observing session a few days before or a
few days after the Leonids for comparison.
For more information about the Leonids 2000, including predictions and
observing tips, please visit LeonidsLive.com. Daily meteor counts and
information about other meteor showers are available at SpaceWeather.com.
======================================================================
(3) U.S. EAST COAST MAY OFFER BEST VIEW OF LEONIDS METEOR SHOWER
>From Ron Baalke <baalke@jpl.nasadot gov>
Steve Roy
Media Relations Department
Marshall Space Flight Center
Huntsville, AL
(256) 544-0034
steve.roy@msfc.nasadot gov
For Release: November 8, 2000
Release: 00-311
North America's East Coast may offer best view of Leonids meteor shower, say
NASA scientists
Six teams of scientists led by NASA's Marshall Space Flight Center in
Huntsville, Ala., will monitor the annual Leonids meteor shower this month
when the phenomenon is brightest over the North American continent.
Part of the monitoring activities will include the launch of a weather
balloon carrying video and audio equipment which will allow scientists and
the public to actually hear what a meteor sounds like as it crashes into
Earth's atmosphere.
The public, particularly along the East Coast, also will be able to look up
and, depending on weather conditions, see perhaps 700 or more shooting stars
per hour.
Three peak times for the showers are forecast for the East Coast -- Nov. 17
at about 3 a.m. EST and again at 11 p.m. EST, and Nov. 18 at about 3 a.m.
EST -- according to Bill Cooke, senior computer scientist at the Marshall
Center.
A Leonids shower happens every year when Earth passes close to the orbit of
the comet Tempel-Tuttle and the debris left in the comet's path. As Earth
travels through the comet dust, the debris burns up in the Earth's
atmosphere resulting in shooting stars or meteors. Some of these dust
streams actually broke away from the comet long ago. Meteors visible this
year date to 1932, 1866 and 1733.
"This year, the Moon will be in the constellation Leo -- practically on top
of the Leonids radiant," said Mitzi Adams, a Marshall Center astronomer.
"Moonlight will make fainter meteors hard to spot, but if there's a strong
outburst, stargazers could see plenty of Leonids in spite of the bright
Moon."
Because this year's peak meteor activity is not projected to reach storm
level -- at least 1,000 meteors per hour -- Marshall scientists will use the
opportunity to test their accuracy at predicting Leonids intensity.
In 1999, a true "storm" occurred when up to 3,700 meteors per hour were
recorded over Israel.
"We can predict within minutes the time the meteors will peak," said
Marshall Space Environment Team researcher Dr. Rob Suggs. "What we have
trouble with is predicting the intensity."
If the intensity of a Leonids shower can be accurately predicted, scientists
will know which way orbiting satellites should be turned to keep them
operating smoothly during meteor activity.
"Satellites are an integral part of our lives now, so anything that affects
these satellites directly affects our lives," Suggs said, citing as examples
communications and television satellites.
To help protect these satellites from the fast-travelling meteors, Marshall
scientists will analyze information from the various monitoring teams and
pass it along to satellite operators.
Although a typical meteor is smaller than a grain of sand, it travels 12
miles (20 kilometers) per second. Leonids are the fastest of all meteors --
traveling at about 44 miles (71 kilometers) per second. At that speed, a
Leonids meteor could travel from New York to Los Angeles in about one
minute.
Heavy Leonids meteor storms are predicted for 2001 and 2002.
"We are getting predictions from models for next year in excess of 10,000
meteors per hour over East Asia and Mongolia," Suggs said. "In 2002,
predictions are in excess of 25,000 meteors per hour over the East Coast of
the United States."
The Marshall Center is NASA's lead center for monitoring and forecasting
meteor showers. Huntsville scientists will begin monitoring Nov. 16, using
two image-intensified camera systems and recording the meteors onto
videotape.
"This year we also have a forward-scatter radar that will allow us to 'hear'
the meteors," Suggs said, explaining that the noises are caused by the
meteors interacting with ionized gas or plasma in the Earth's atmosphere.
Besides monitoring the Leonids from Huntsville, Marshall scientists also
will coordinate monitoring teams at the following locations:
* Mount Allison Observatory in New Brunswick, Canada.
* Elginfield Observatory at the University of Western Ontario, in London,
Ontario.
* The University of Regina in Saskatchewan, Canada.
* U.S. Air Force LINEAR (Lincoln Near-Earth Asteroid Research) Observatory
in Socorro, N.M.
* Calar Alto Observatory near Almeria, Spain.
In addition to the observing teams, Marshall scientists, weather permitting,
will launch a 10-foot (3-meter) diameter weather balloon from Marshall's
Atmospheric Research Facility at 12:30 a.m. CST on Nov. 18. The balloon will
ascend approximately 20 miles (32 kilometers), carrying a sensitive camera
for capturing high-resolution television pictures of the meteors. During the
three-to- four-hour flight, the television pictures can be viewed online at
the Marshall Center's Science Directorate Web site at:
http://www.leonidslive.com
The balloon also will carry a very low frequency radio receiver that will
allow visitors to the Web site to hear the "whistlers" and other bizarre
noises that meteors might make as they enter the Earth's atmosphere.
On-board transmitters will allow local amateur radio operators, or "hams,"
to track and retrieve the balloon.
Note to Editors/News Directors: Media are invited to schedule a visit with
the Marshall Center's Leonids monitoring team during operations, including
the balloon launch on Nov. 18. To attend the balloon launch or talk with the
Leonids monitoring team, news media representatives should contact Steve Roy
of the Marshall Media Relations Department at (256) 544-0034, or beeper
1-800-821-9641. A cellular phone number will be made available to interested
media for 24-hour, up-to-date, information during the Leonids monitoring.
Interviews, photos and video supporting this release are available to news
media representatives by contacting Roy. For an electronic version of this
release, digital images or more information, visit Marshall's News Center on
the Web at:
http://www.msfc.nasadot gov/news
Print quality photos of the balloon launch preparations will be available
for downloading from the Marshall Center Web site at a future date.
[NOTE: An image supporting this release is available at
http://www1.msfc.nasadot gov/NEWSROOM/news/photos/2000/photos00-311.htm]
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