CONFIRMED - 11 November 1999


     "The observed peak time coincides almost perfectly with the peak
     time of 2:08 am Greenwich Mean Time predicted by Asher and
     McNaught, indicating that the activity was due to the dust trail
     created the Leonids' parent comet, Tempel-Tuttle, about 100 years
     ago (i.e., 3 revolutions ago of the Comet around the Sun)."
         -- Marc Gyssens, International Meteor Organization
            18 November 1999

    Benny J Peiser <>

    Marc Gyssens <>

    Ron Baalke <>




From Benny J Peiser <>

Britain woke up this morning to the usual lamentation about the
weather. What made things worse, however, was the fact that most people
in the country weren’t able to enjoy the display of the Leonids meteor
storm. Bad weather had hampered the view. Yet instead of moaning, we
should celebrate a remarkable accomplishment by two young British

David Asher, an English astronomer based at the Armagh Observatory 
(Northern Ireland) and Robert McNaught, a Scottish astronomer based in 
Siding Spring Observatory (Coonabarabran, Australia) have made history
by solving a scientific puzzle that has bewildered the astronomical
community for exactly one hundred years: How to forecast the seemingly
irregular Leonids meteor storms.

Ever since the widely predicted Leonids failed to appear in the morning
of November 16, 1899, their erratic behaviour has been viewed as
somewhat of an enigma that seemed difficult to elucidate. Looking back,
the unsuccessful prediction of 1899 led to a public relations fiasco
for the astronomical community: "... the failure of the Leonids to
return in 1899 was the worst blow ever suffered by astronomy in the
eyes of the public, and has indirectly done immense harm to the spread
of the science among our citizens." (Charles Olivier, Meteors, 1925)

After one hundred years of endeavours to get a grip on the capricious
Leonids, Asher and McNaught have pulled off a major success! Their
prediction for the 1999 Leonids, based on their "dust trail theory" has
been confirmed - at least regarding the exact timing of the peak
activity. McNaught & Asher predicted (see CCNet 10 November 1999) the
peak activity of the Leonids to occur this morning at about 2.08 am UT.

"For the 3-rev trail encounter in 1999, the time of maximum is
predicted to be at Nov 18, 02:08 UT in the Mediterranean region, with
an uncertainty of around 5 minutes. The time of maximum is dependent on
location, with the peak predicted at 01:58 in South Africa and 02:14 in
northern Scandinavia."

As Marc Gyssens from the International Meteor Organization points out
in the IMO press release (see below), the observed peak time coincides
almost perfectly with the peak time of 2:08 am Greenwich Mean Time
predicted by Asher and McNaught, "indicating that the activity was due
to the dust trail created the Leonids' parent comet, Tempel-Tuttle,
about 100 years ago (i.e., 3 revolutions ago of the Comet around the

While this is an impressive confirmation of their theory, it is
interesting to note that their prediction of the highest hourly rate
(Zenithal Hourly Rate, or ZHR), expected to be in the 500 range,
could not be validated: In fact, early reports suggest that the peak
activity corresponded with an hourly rate up to ten times higher than
the predicted number. Evidently, the Leonids never fail to surprise us.

The historical achievement by Asher & McNaught should not be
depreciated by this minor drawback. What their success proves is that
astronomical predictions are progressively improving. The time will
come when we will be able to sufficiently understand, and ultimately
yield control over, the dynamics of cometary and meteoric activity that
affect our cosmic environment.

Well done, David and Rob!

Benny J Peiser


From Marc Gyssens <>

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

Leonid meteor storm materializes around expected peak time (UPDATE)

Experienced visual observers watching near Malaga and at the Sierra
Nevada Observatory in Spain and near the Gorges du Verdon in the French
Provence report that Leonid meteor activity peaked at up to 30 meteors
per minute shortly after 2 am Greenwich Mean Time. This activity was
characterized by a lot of faint meteors and almost no fireballs.

Meteor astronomers reduce the actual numbers of meteors seen to a
standard value, called the Zenithal Hourly Rate (ZHR), which takes
into account the quality of the sky as well as the direction from
which meteoroids enter the atmosphere. The peak activity reported by
the abovementioned groups of observers corresponds with a ZHR around
5000, which is considerably more than what most meteor observers had
hoped for (around 1000).

Preliminary reports of other observing groups at Tenerife, Canary
Islands, near Valencia in Spain, and in Jordan confirm the picture
sketched above.

Radio observations from Japan and the Czech Republic also indicate a
peak time between 2:00 and 2:10 am Greenwich Mean Time.

The observed peak time coincides almost perfectly with the peak time
of 2:08 am Greenwich Mean Time predicted by Asher and McNaught,
indicating that the activity was due to the dust trail created
the Leonids' parent comet, Tempel-Tuttle, about 100 years ago
(i.e., 3 revolutions ago of the Comet around the Sun).

Marc Gyssens
International Meteor Organization

Below is a more technical description of the observed Leonid peak


       I M O   S h o w e r   C i r c u l a r


               LEONID Activity 1999

Visual observations of the 1999 Leonids revealed
a distinctive peak with a ZHR of about 5000 on
November 18, 2h05m +/-10m UT (solar longitude
235.287 +/- 0.007, eq. 2000.0). ZHR levels
were above 1000 from roughly 1h30m UT to 3h00m UT
corresponding to 235.26 to 235.32 degrees in solar

All observers who were able to view the peak under good
sky conditions reported an abundance of faint meteors and
a relative absence of fireballs. Some observers noticed
a drop in the population index (i.e., a larger fraction of
brighter meteors) after the peak.

Reports from Mohammad Odeh (Jordanian Astronomical Society)
and Casper ter Kuile (Dutch Meteor Society, observing near
Valencia, Spain) are very consistent with the picture sketched

In addition, radio data from K. Maegawa (Toyokawa Meteor Observatory,
Aichi, Japan) reported by Kazuhiro Suzuki and the backscatter
radar data from Ondrejov Observatory (Czech Republic) reported by
Petr Pridal and Rosta Stork yield a peak time between 2h00m UT
and 2h10m UT.

It seems that the peak time of 2h08m UT predicted by Asher/McNaught
is confirmed within a margin of at most a few minutes, although the
observed activity is significantly higher. It is reasonable to
conclude that the peak activity has been caused by the 3-revolutions
old dust trail of 55P/Tempel-Tuttle.

The following observers have contributed data immediately
after the event, from which the ZHR profile given below
has been derived:

Per Aldrich, C.L. Chan, Asdai Diaz, Yuwei Fan, Fei Gao,
Lew Gramer, Andre Knoefel, Wen Kou, Alastair McBeath,
Tom Roelandts, Sirko Molau, Renke Song, Wanfang Song,
Honglin Tao, Dan Xia, Dongyan Zha, Jinghui Zhang, Yan
Zhang, Jin Zhu.

(For groups of observers, only the name of the contributing
observer has been mentioned.)

Date   Period (UT)  ZHR  +-
Nov 17  0600-1000   16    2
Nov 17  1600-2010   30    5
Nov 17  1900-2200   53   14
Nov 18  0030-0100  130   90
Nov 18  0100-0115  490  230
Nov 18  0115-0130  770  160
Nov 18  0130-0145 1040  660
Nov 18  0145-0202 4100  840
Nov 18  0200-0215 5000 1100
Nov 18  0212-0230 2400  280
Nov 18  0243-0247 1100  160
Nov 18  0320-0330  470   70
Nov 18  0420-0430  180   40

ZHRs are computed with a population index of 2.0, zenithal
exponent of 1.0.

Marc Gyssens, 1999 November 18, 7h UT.


From Ron Baalke <>

Huge Fireball Dazzles Midwest
Marshall Space Flight Center

November 17, 1999: Tuesday night, on an Illinois highway east of Chicago,
traffic slowed to a crawl as motorists peered at an extraordinary fireball
blazing overhead.

A brilliant fireball attracted stares across the eastern U.S. Tuesday
night. It could be a taste of things to come when the Leonids meteor
shower peaks late Wednesday night and Thursday morning.

"It was of the most beautiful meteors I have ever seen," said Jamie
Dresser, who was driving home from work just after 6 pm CST. "It was so
bright that it lit up the sky for quite a distance. There was a blue
corona ... and it was actually trailing fire for quite a distance. I
sincerely look forward to driving home the next few nights!"

Above: The above 533 KB QuickTime simulation illustrates the
relationship during the Leonids meteor shower between the earth, comet
Tempel-Tuttle's dust field, and the constellation of Leo. The size of
the earth and sun have been exaggerated for clarity. When the earth
passes through Tempel-Tuttle's dust field every November 17-18, the
dust particles stream into our atmosphere and burn up as meteors. The
red arrow during the simulation indicates that a ground-based observer
would perceive the meteors as coming from a point (called the
"radiant") within Leo, hence the name Leonids.

Hundreds of reports like this one are pouring in from all over the mid
western United States. Thousands of commuters and star gazers saw what
astronomers call an "Earth grazer" -- a meteoroid or piece of space
debris that travels nearly parallel to Earth's surface as it
disintegrates in our atmosphere. Earth grazers are slow moving and
feature vibrant colors in their long beautiful tails. This one was
spotted between 5:50 and 6:05 CST as it sped over Wisconsin, Michigan,
Illinois, Ohio, Kentucky, New York and several other states.

Tuesday night's fireball was so bright that it was first noticed by
many observers while they were inside brightly lit buildings.

"I was sitting in a Wendy's facing outside and saw the bright orange
light in the sky," recounts Wendi S. Abbott of Cincinnati, OH. "I have
no idea how long it lasted, but I had time to jump up, race over to the
window and ask the family sitting there if they were seeing what I was
seeing. The father said it was just a reflection in the window, but
quickly changed his mind. It finally broke apart in about 3 or 4 pieces
before it died out. What an incredible sight! If this is any indication
of what's to come, this will definitely be a 'once in a lifetime

The trajectory of the fireball was similar in appearance to an
aircraft, flying low and level across the horizon from west to east.
Many observers reported seeing the meteor fragment into many iridescent
pieces that traveled in a line like a string of Christmas lights.

Could this be a taste of things to come in the next 24 hours? Possibly.
The Leonid meteor shower is expected to peak this Thursday morning when
the Earth slices through the debris stream of comet Tempel-Tuttle
around 0200 UT on November 18. Last year a shower of Leonid fireballs
(meteors brighter than magnitude -3) dazzled observers in Europe and
the Americas. In 1999 many experts anticipate an even better show. No
matter where you live, the best time to watch will be between midnight
and dawn on Thursday. On Wednesday evening, November 17, before the
constellation Leo rises, star gazers could be treated to more Earth
grazers as Leonid meteoroids arc over the horizon.

With the Leonids just around the corner, it may seem surprising that
Tuesday's fireball was probably not a Leonid. Leonid meteors emanate
from a point in the sky within the constellation Leo, which rises above
the eastern horizon around midnight. At the time of the fireball
sighting Leo was about 35 degrees below the northern horizon, which
means that Leonid Earth-skimmers appearing over the horizon would
travel roughly north to south. Most observers reported that the
November 16 fireball moved west to east. While it is possible that this
meteoroid was a part of the debris stream of comet Tempel-Tuttle (the
parent of the Leonids), it is far more likely to be an unrelated,
sporadic meteor or perhaps a piece of "space junk" decaying from
low-Earth orbit.

Whatever this fireball was, observers around the world have been seeing
genuine Leonids for over 24 hours. The Leonids Environment Operations
Center at the NASA/Marshall Space Flight Center is managing data from a
global network of observers coordinated by the US Air Force and the
University of Western Ontario. Since early Tuesday morning trained
spotters have filed reports of 8 to 86 meteors per hour (ZHR). In most
years, 86 meteors per hour would be considered a substantial shower,
but this could be the year for a full-fledged Leonids storm. Only time
will tell if predictions of more than 1000 meteors per hour will come
true. One thing is sure, the place to be before dawn on Thursday
morning, November 18, is outdoors and looking up!



Nov. 17, 1999
Kathleen Burton
NASA Ames Research Center, Moffett Field, CA
(Phone: 650/604-1731, 650/604-9000)

Laura Lewis
NASA Ames Research Center, Moffett Field, CA
(Phone:  650/604-2162, 650/604-9000)

RELEASE:  99-74


Astrobiologists began their first airborne observation night to study
the Leonid meteors on Nov. 16, as the Earth began to enter the debris
train left by the periodic comet 55P/Tempel-Tuttle.

At 21:50 GMT, on Nov. 16, the ARIA and FISTA, two United States Air
Force planes, departed from Mildenhall in the United Kingdom for Tel
Aviv Israel. During the overnight flight to Israel, the two aircraft
flew approximately 80-100 miles apart from each other and as high as
38,000 feet.

The mission flight path took the scientists southwest of Mildenhall,
over Lands End and out of the United Kingdom.  The aircraft then
turned south to fly over north central Spain, and then turned east to
fly over Barcelona. The flight continued over Corsica, across the
boot of Italy, over central Greece, and across the Mediterranean into
Israel.  ARIA and FISTA landed in Tel Aviv at 04:20 GMT Nov. 17.

The scientists and crew members aboard the FISTA and ARIA had a very
successful first night of their Astrobiology mission. In addition to
observing meteors, the team took measurements of air glow, observed
and recorded lightning over Spain, and saw Jupiter and Saturn clearly
in the night sky. They also successfully demonstrated that live
images of the meteors could be sent from the plane, over the TDRS
satellite, to the Internet.

The science team on the FISTA was thrilled with the collected data. 
"By the end of this first mission night we have already exceeded the
number of meteors we observed with our mid-infrared instruments
during the entire 1998 mission over Japan," said Peter Jenniskens,
Leonid mission chief scientist.

The mid-infrared spectrographs, contributed by the Aerospace
Corporation, are being used to detect the unique fingerprint of
complex organic matter - like that required for life - in meteors. 
The instruments are also expected to provide information on the
formation of solid particles and the heat of the meteors as they
enter the atmosphere.

"A total of 10 meteors crossed the field of view of our
spectrograph," reported George Rossano, a researcher on the FISTA
aircraft.  "I'm hopeful that these meteors will result in the first
successful mid-infrared fingerprint of a meteor."

On ARIA, the flux measurement team counted meteors without actually
looking out the window to see them; researchers wore goggles that
displayed images from cameras that were pointed out of the airplane's
windows.  The number of Leonid meteors and sporadic meteors counted
by each team member was entered into a laptop computer.

Jane Houston, a member of the flux measurement team and one of
several amateur astronomers on the mission, explained how the team
differentiated between Leonid and sporadic meteors. "The Leonid
meteors radiate from the constellation Leo, while sporadic meteors
fall randomly across the sky."

Each of the team members' laptop computers was linked to a central
laptop computer, and near real-time data indicating the total number
of meteors counted was provided. "The methods developed to count
meteors for this mission could revolutionize the way future meteor
showers are monitored," claimed Kelly Beatty, another amateur
astronomer on the flux measurement team.

At the end of the night, the flux team reported observing
approximately 14 sporadic meteors per hour and a Leonid zenith hourly
rate of approximately 15 meteors per hour. The zenith hourly rate is
the number of meteors an observer on the ground would see under
perfect observing conditions.

"These rates for Leonids are almost twice as high as those we would
normally see the night before the expected peak," explained Dr.
Jenneskins, "I'm optimistic this is an indication that we will see a
good storm tomorrow night."

The peak of the Leonid storm is expected at 02:00 GMT Nov. 18 over
Europe and the Middle East. The international science team studying
the Leonids will be flying from Tel Aviv to Lajes Airbase during the
storm peak. It may be possible to see the Leonid meteor storm in the
United States on the night of Nov. 17 (9:00 p.m. EST).  However, best
viewing may actually be in the predawn hours of Nov. 18.

The Leonid Multi-instrument Airborne Campaign is an Astrobiology
mission from NASA Ames Research Center at Moffett Field, CA.  The
campaign is jointly funded by the United States Air Force and the
National Aeronautics and Space Administration. Astrobiology is an
interdisciplinary field that studies the origin, evolution,
distribution and destiny of life in the universe.

For current information about the Leonid Multi-instrument Airborne
Campaign, and to watch live Leonid coverage on the Internet, visit:



Nov. 17, 1999
Kathleen Burton
NASA Ames Research Center, Moffett Field, CA
(Phone: 650/604-1731, 650/604-9000)

Jane Platt
Jet Propulsion Laboratory, Pasadena, CA
(Phone:  818/354-0880)

RELEASE:  99-75

Jupiter's history may be much older and colder than previously
believed, according to newly released findings from the descent probe
of NASA's Galileo spacecraft published in the Nov. 18 edition of the
journal Nature.

"This new information might shake up our view of how the solar system
formed," said Dr. Tobias Owen, astronomy professor at the Institute for
Astronomy of the University of Hawaii, Honolulu, HI, and a scientist on
the Galileo probe neutral mass spectrometer instrument team.  When
Galileo arrived at Jupiter on Dec. 7, 1995, and dropped a probe into
the atmosphere of the huge, gaseous planet, the mass spectrometer
measured the chemical composition of Jupiter's atmosphere.

The spectrometer detected in Jupiter's atmosphere higher than expected
concentrations of argon, krypton and xenon, three chemical elements
called noble gases because they are very independent and don't combine
with other chemicals. Tiny traces of these gases are found in Earth's
atmosphere, and argon is sometimes used like neon in advertising signs.

The discovery of these gases in such high quantities at Jupiter raises
questions about how they got there.  "In order to catch these gases,
Jupiter had to trap them physically by condensation or freezing," Owen
said.  This process, he said, requires extremely cold temperatures of
about -240 degrees Celsius (-400 degrees Fahrenheit), colder than the
surface of Pluto, the planet farthest from the Sun. Planetesimals
(small objects orbiting the Sun) in the Kuiper Belt beyond Pluto would
be this cold, but Jupiter is more than six times closer to the Sun and
thus is much warmer.  For this reason, Jupiter could not have been the
site where the three noble gases were originally trapped.

"This raises some intriguing possibilities," Owen said. "One
explanation suggests that Jupiter was formed out in the area around the
Kuiper Belt and dragged inward to its present location. Another
possibility is that the solar nebula, a huge cloud of gas and dust from
which our solar system formed, was much colder than scientists
believe," he said. -more-

"A third hypothesis proposes that the solid materials that brought
these noble gases to Jupiter began forming in the original huge,
interstellar cloud of gas and dust even before it collapsed to form the
solar nebula. That would make these icy materials older and more
primitive than we had expected," he said.

"If either of the last two hypotheses proves to be correct, it would
suggest that giant planets can form closer to their stars than current
theories predict," Owen said.  "This could help explain the new
observations of planetary systems around other stars, in which such
close-in giant planets are relatively common."

"These new Galileo probe results provide new insights into how planets
form in the solar system and around other stars," said Galileo project
scientist Dr. Torrence Johnson of NASA's Jet Propulsion Laboratory,
Pasadena, CA.

"Measuring the composition of Jupiter's atmosphere was a primary
scientific objective of the probe, because we knew it could change our
understanding of Jupiter's formation and evolution," said Galileo probe
project scientist Dr. Richard Young of NASA Ames Research Center,
Moffett Field, CA. "These latest probe results have done exactly that,
and the measurements are the sort that could only have been obtained by
in-situ measurements from an entry probe."

Owen's co-authors on the Nature article are: Drs. Paul Mahaffy and
Hasso Niemann of NASA's Goddard Space Flight Center, Greenbelt, MD;
Drs. Sushil Atreya and Thomas Donahue of the University of Michigan,
Ann Arbor, MI; Dr. Akiva Bar-Nun of the University of Tel Aviv, Israel;
and Dr. Imke de Pater of the University of California, Berkeley, CA. 
Although the data were collected by the Galileo probe in December 1995,
careful and thorough analysis was necessary in Earth laboratories to
verify the findings.

When it dropped 156 kilometers (97 miles) through Jupiter's atmosphere,
the Galileo probe relayed data back to the main Galileo spacecraft more
than 209,215 kilometers (130,000 miles) overhead for storage and
transmission to Earth. The probe descended deeper into the atmosphere
than expected, but was finally overcome by Jupiter's high temperatures
and pressures.

The Galileo spacecraft, meanwhile, has been orbiting Jupiter and its
moons for nearly four years, beaming back to Earth thousands of
pictures and a wealth of scientific data. Its two-year, primary mission
ended in December 1997, but it was followed by the current, two-year
extended mission. The Galileo Project is managed by the Jet Propulsion
Laboratory, Pasadena, CA; the Galileo atmospheric probe is managed by
NASA Ames Research Center, Moffett Field, CA.  Further information and
images about the Galileo mission to Jupiter are available on the
Internet at:

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From Johannes Andersen <>

The character and purpose of the so-called "Torino Scale" and its
"adoption" by the IAU has been the subject of some recent discussion on
CCNet. While we cannot endeavour to correct every misunderstanding
arising in the grey literature, it seems useful to provide a
clarification here.

From our point of view, the Torino Scale is a useful concept in dealing
with the public and the media for two reasons. First, it highlights the
vast range of consequences associated with impacts of different
magnitude, all of which are possible at equally different, if all
microscopic levels of probability. And second, it immediately makes the
point that no known NEO presents any measurable danger to Earth in the
foreseeable future.

As such, it is a great improvement over the concept of "Potentially
Hazardous Asteroids" (PHAs), which was useful when orbit computation
methods were less refined and anything approaching was potentially
dangerous. At the current state of the art all PHAs are Perfectly
Harmless Asteroids, and the old interpretation of the acronym is
misleading to the public.

In a semi-scientific context, the Torino Scale is also useful in
conveying the message to the public that the offer of IAU peer review
extends to any discovery of an NEO that is not patently harmless.
Exactly how the experts decide what is what is a concern for those
experts. As a package, the review mechanism and the Scale are a real
contribution to the professional handling of both the scientific and
political aspects of NEO discoveries by the international community,
negotiated by the IAU Working Group on NEOs. We find this result to be
a credit to the IAU, and the public deserves to know that the Union is
acting responsibly on this sensitive issue.

In a purely scientific context, a classification scheme that places all
known objects in Category 0 is, of course, not exactly a breakthrough.
As knowledge progresses, we shall no doubt see either a revision (or
several) of the Torino Scale, or the development of more refined
schemes, based on the rich variety of orbital data that are now
becoming available. This will go on happily within the IAU NEO
community as a continuing process as scientific frontiers expand.
Attempts to interpret the IAU "adoption" of the Scale as explained
above as a sanctification of every technical aspect of its first
incarnation or as an iron rule on its use in scientific studies of NEOs
is, first, misguided, and second, doomed to failure in the real world
of science - the home territory of the IAU.

Johannes Andersen                           Hans Rickman    
General Secretary, IAU             Assistant General Secretary, IAU

IAU/UAI Secretariat
Institut d'Astrophysique              Tel:     +33 1 4325 8358
98bis, Bld. Arago                     Fax:     +33 1 4325 2616
F - 75014 Paris                       E-mail:
France                                WWW:

CCCMENU CCC for 1999

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