PLEASE NOTE:


*

CCNet DIGEST, 19 May 1999
-------------------------

(1) NASA INCREASES IMPACT PROBABILITY FOR ASTEROID 1999 AN10 BY
    A FACTOR OF 100
    Benny J Peiser <b.j.peiser@livjm.ac.uk>

(2) THE CONTINUING STORY OF ASTEROID 1999 AN10
    Ron Baalke <baalke@ssd.jpl.nasa.gov>

(3) CONTROVERSIAL ASTEROID MAY MAKE CLOSE PASS IN 2027
    EXPLOREZONE, 18 May 1999

(4) NEW ASTEROID DATA SHOULD NOT BE PUBLICIZED
    Clark Chapman <cchapman@swri.edu>

(5) WERE SATELLITE OWNERS LUCKY LAST YEAR? MORE INTENSE LEONID BOMBARDMENT
    PREDICTED FOR 1999
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(6) US ASTRONOMER DISCOVERS 18TH MOON ORBITING URANUS
    Andrew Yee <ayee@nova.astro.utoronto.ca>


=============
(1) NASA INCREASES IMPACT PROBABILITY FOR ASTEROID 1999 AN10 BY
    A FACTOR OF 100

From Benny J Peiser <b.j.peiser@livjm.ac.uk>

In a press statement released yesterday (see below), Paul Chodas of NASA's
Near Earth Object Program Office confirmed the latest MPC calculations
regarding asteroid 1999 AN10. According to Chodas, the new observational
data provides a "considerably improved orbit" which shows that the
object might come as close as 37,000 km on August 7, 2027. Whilst the
probability of a collision in that year is "essentially zero", Paul Chodas
underlines that "the probability of collision in 2039 has now increased
to about 1 chance in 10 million."

It is important to stress that NASA's revision by a factor of 100 does
not make AN10 much more likely to be an actual threat in fourty years
time. A chance of 1 in 10 million is still extremely small. It seems
more likely that additional observations of AN10 in the next few months
will reduce rather than increase the overall impact risk.

In view of these new findings, Clark Chapman has again questioned the
wisdom of making this impact risk data public. Although his criticism
is clearly directed at the CCNet (see his statement below), it applies
just as much to the much wider publicity NASA has decided to give to
their own impact threat calculations.

Nevertheless, I hope this is the right place to answer Clark's main
objection as to *why* I believe that there was and is a legitimate
scientific argument for publicising the data in the first place.

When Andrea Milani, Steven Chesley and Giovanni Valsecchi, the authors
of the original paper on 1999 AN10, explained to the reviewers of their
paper why they did not wish to make their results public, they were
under the impression that "the asteroid is now almost impossible to
observe, and even if it were observed new astrometric positions taken
now would not contribute significantly to the improvement of the orbit"
(CCNet, 20 April 1999).

Richard Binzel (MIT) and David Morrison (NASA) simarly claimed that
there "was no reason for this finding to be disseminated publicly.
[...]  the asteroid is already in a part of the sky where it cannot
be observed for months, so there is no such urgency" (Boston Globe, 14
April 1999).

In contrast to these assumptions, an amateur astronomer in Australia has
had no problems whatsoever to observe 1999 AN10; what is more,
the new astrometric positions he provided have significantly improved
the asteroid's orbit. It would thus appear that the original assumption,
on which the decision not to publish the reviewed findings was made,
was mistaken.

At this point I should like to add a correction to yesterday's posting.
Frank Zoltowski, who made the observations, is not, as stated yesterday,
an Australian, but an American amateur astronomer currently working
in South Australia. His observations prove that 1999 AN10 can be easily
tracked even with a small 30-cm telescope - it's not like one needed
some huge professional telescope to solve this problem. However, it is
more than likely that Frank Zoltowski would never have searched for AN10
without the publicity surrounding the controversial web paper.

In fact, experience has shown that if one does not specifically draw
attention to a particularly interesting asteroid, it might simply not
get observed when visible in the sky (as in the classical example of
asteroid 1997 XF11). In short, the worst that could have happened in
the case of AN10 would be the lack of any additional observations prior
to the publication of the web paper.

To postpone the publication of such relevant data until published in a
peer reviewed journal could have meant the witholding of this information
for up to six months. As a result, many observers might never have known
that the current problem with AN10 could be solved by observations this
summer. In this case, we might have had to wait until the object becomes
observable again in 2004.

That's why I believe Andrea Milani, Steven Chesley and Giovanni Valsecchi
should have informed the NEO search community and the general public about
their findings once they were generally confirmed by independent reviewers.

Benny J Peiser

==============
(2) THE CONTINUING STORY OF ASTEROID 1999 AN10

From Ron Baalke <baalke@ssd.jpl.nasa.gov>

The Continuing Story of Asteroid 1999 AN10
http://http://neo.jpl.nasa.gov/news/news017.html

New observations are now available for asteroid 1999 AN10, which is
gradually moving away from the glare of the Sun. The new data allow a
considerably improved orbit to be calculated for this potentially
hazardous object, and the revised predictions indicate that this
kilometer-size asteroid could pass particularly close to the Earth on
August 7, 2027. The passage in 2027 could be as close as 37,000 km from
the Earth's center (just 19,000 miles above the Earth's surface), but no
closer. The miss distance is still very uncertain, and the asteroid
could easily pass well outside the Moon's orbit. The probability of a
collision in 2027 is essentially zero.

The accompanying diagram (http://neo.jpl.nasa.gov/neo/an10.gif> shows
the uncertainty in the predicted close approach in 2027.  The asteroid
must pass through the plane of the diagram somewhere within an
extremely elongated uncertainty ellipse, which appears simply as a line
segment. (To be precise, the ellipse as drawn is a three-sigma linear
confidence boundary.) The center of the ellipse is indicated by the
plus sign, which is located at a nominal distance of 58,000 km from the
center of the Earth. The minimum distance between the ellipse and the
Earth center is 37,000 km.

There is still a very remote possibility that asteroid 1999 AN10 could
pass by Earth in 2027 in such a way as to return in the year 2039 on an
impacting trajectory.  First identified by researchers Andrea Milani,
Steven R. Chesley and Giovanni B. Valsecchi, this scenario is still
exceedingly unlikely, but the probability of collision in 2039 has now
increased to about 1 chance in 10 million. The post-2027 (Monte Carlo)
analysis of this object's motion will continue.

Paul W. Chodas
Research Scientist
Near Earth Object Program Office
Jet Propulsion Laboratory
May 18, 1999

==================
(3) CONTROVERSIAL ASTEROID MAY MAKE CLOSE PASS IN 2027

From EXPLOREZONE, 18 May 1999
http://www.explorezone.com/archives/99_05/18_asteroid_an10.htm

By Robert Roy Britt, explorezone.com

05/18/99: New observations and calculations show that an asteroid
scientists had previously warned had an extremely small chance of
hitting the Earth in 2039 may make a close pass in 2027. Researchers say
a close pass could cause the asteroid's path to be altered by Earth's
gravity, increasing the chances of an impact on some later orbit.

Asteroid 1999 AN10 first made news on April 13 of this year when Dr.
Benny J. Peiser, a researcher who focuses on neo-catastrophism at
Liverpool John Moores University, wrote in his newsletter about a
scientific paper on the asteroid. Peiser's newsletter, along with
explorezone.com's subsequent story, contributed to significant
controversy and debate over the publication of the research contained in
the paper, which was posted on a Web site but was not intended to be
made public. [See the original story]

Today, Peiser tells of new observational data that shows the asteroid,
which is a little less than a mile wide, may make a very close approach
in 2027 -- a mere 23,600 miles. Or, researchers said, the distance could
be much greater.

The fresh calculation for the possible close approach was made by Brian
Marsden and Gareth Williams of the Minor Planet Center at the
Smithsonian Astrophysical Observatory. The new data was supplied by
Australian astronomer F. Zoltowski.

"We already knew from the paper by Andrea Milani, Steven Chesley and
Giovanni Valsecchi that an impact was not possible in (2027)," Peiser
wrote in his newsletter today. "But the new calculations confirm their
initial speculation that the asteroid might approach within the Earth's
sphere of influence and thus could, theoretically, be perturbed in such
a way that it might impact some years later."

Peiser said uncertainty in the new calculations make it impossible to
know if the chances for an impact have increased. More observational
data will be required, he said.

Marsden and Williams, in discussing the new calculations, said
"additional observations during the next several months will be useful,
because (after that) there are no other reasonable observing
opportunities until at least 2004." ez

================
(4) NEW ASTEROID DATA SHOULD NOT BE PUBLICIZED

From Clark Chapman <cchapman@swri.edu>

Dear Benny,

Your continuing emphasis on 1999 AN10 is incompatible with the facts
concerning that asteroid.  As your recent "Special" notes, there is no
chance of an impact in 2027 (or before) and there are plenty of
opportunities to observe it then, and long beforehand, to ascertain
where it might go in the decades beyond. So *why* are you so insistent
on the urgency of publicizing it. When any conceivable danger from AN10
(and a rather minucule chance, at that) is decades from now, why can't
the observers and orbit calculators take their time to reach the right,
verified conclusions, outside of the glare of public hype?

Thanks to lessons learned last year from XF11, PHA cases like AN10 are
now routinely having their future "near misses" calculated and there
was never cause for alarm.  There will be many future cases of
mile-wide NEO's being discovered that will have rather close passes to
the Earth during the next century, and even more cases of smaller NEO's
making such passes.  And quite a few of them will be calculated to have
impact probabilities with Earth during the next century in the range of
1 chance in a hundred thousand to 1 chance in  a million.  After all,
the probability of impact of any one of the ensemble of kilometer-sized
and larger NEO's striking Earth in the next century is something like 1
in a thousand. As we discover an increasing fraction of these bodies,
it is our duty to demonstrate that their probability of hitting is, in
fact, zero rather than a chance in a million...and we should go about
this task dispassionately. After all, there is thankfully only that
small, 1-in-a-thousand chance that any of them will actually be
found to be on a collision course.

If we continue to generate alarms and headlines each time a body is
found that, temporarily, has a 1-in-a-million chance of hitting, we
will have so bored and saturated the public with false alarms that we
might be in danger of having a *real* alarm discounted.

Clark R. Chapman
Southwest Research Inst., Boulder CO, USA

===============
(5) WERE SATELLITE OWNERS LUCKY LAST YEAR? MORE INTENSE LEONID BOMBARDMENT
    PREDICTED FOR 1999

From Andrew Yee <ayee@nova.astro.utoronto.ca>

Aerospace Corporation
El Segundo, California

News Release: May 16, 1999

Leonid Conference Participants Ask: "Were We Lucky Last Year?"

"Were we lucky last year?"

That is a question asked at the second Leonid Meteoroid and Satellite
Threat Conference held May 11-13 in Manhattan Beach, California.

The answer -- "maybe" -- was about as clear cut as possible given the
unpredictability of meteor showers.

About 100 satellite owners and operators from the international space
community attended the event, sponsored by The Aerospace Corporation and
the American Institute for Aeronautics and Astronautics. These included
civil, commercial and military participants.

None reported damage to their satellites from the Nov. 1998 Leonids
shower, though there were reports of impacts from the tiny but zippy
particles that make their presence known every 33 years or so.

Because the Leonids, the fastest meteoroids that visit Earth, normally
occur with strength in pairs of years, preparations are being made for
the 1999 event.

And some scientists at the conference predicted a more intense
bombardment on Nov. 17/18 than was experienced last year at the same
time.

This Year?

At least two conference presenters predicted a storm-level concentration
of meteoroids for Nov. 1999. But even at storm-level, the consensus was
that the 650 operational satellites on orbit will not be significantly
threatened, though the uncertainty factor leaves open the possibility.

Satellite controllers said they will be making plans for this year's
event based on their experience in 1998 and on what they learned at the
conference where a great deal of information was shared. Most operators
said they will make adjustments and improvements to their plans.

The 1998 Leonid shower galvanized those in the satellite community to
action and a new awareness about threats from the space environment has
emerged. One scientist at the conference said the 1998 event was "a
wakeup call" for satellite operators. This wakeup call and the response
by the satellite community represented "the real success" achieved,
another participant said.

Space Weather

Included in this year's conference was a session on solar activities and
the significant threat posed by the solar maximum due in the
spring-to-summer period in 2000.

David K. Lynch, Ph.D., technical chair of the conference, announced that
another Leonids conference will be held in 2000 with increased emphasis
on the areas of space weather, space debris and satellite operations.

Meanwhile, scientists who monitored the Leonids in 1998 from Mongolia,
Australia, the air and other locations said they plan to repeat their
exercises this year, once again employing sophisticated sensors and
cameras.

Called For

Among actions called for at the conference were:

   * establishment of an independent "clearinghouse" for collection and
     distribution of information on meteoroids and other threats from the
     space environment
   * creation of better meteoroid prediction models
   * more focus on the role of sporadic meteoroids
   * a satellite-based meteor-watch capability
   * new techniques to track meteoroids

Other information on the Leonids phenomenon is available at
   http://www.aero.org/leonid/

==================
(6) US ASTRONOMER DISCOVERS 18TH MOON ORBITING URANUS

From Andrew Yee <ayee@nova.astro.utoronto.ca>

News Services
University of Arizona

Contact:

Erich Karkoschka Lunar and Planetary Lab
University of Arizona
Tucson, AZ 85721-0092
Phone: (520) 621-3994
Fax: (520) 621-4933
E-mail: erich@pirl.lpl.arizona.edu

May 18, 1999

UNIVERSITY OF ARIZONA RESEARCHER DISCOVERS 18TH MOON ORBITING URANUS

An Arizona scientist has discovered an 18th moon orbiting the planet
Uranus, the International Astronomical Union announced today. Until
now, Saturn has been the only planet in our solar system known to have
as many as 18 satellites.

Erich Karkoschka, a researcher at the Lunar and Planetary Lab of The
University of Arizona in Tucson, made the discovery. The newly found
moon is the first satellite of Uranus discovered in 1999 but will still
be designated as Satellite 1986 U 10 (short S/1986 U 10).

"This discovery is very unusual," Karkoschka said. "Typically,
satellites are found within days after the discovery image has been
taken. In this case, the discovery image is more than 13 years old."

The interplanetary spacecraft Voyager 2 took seven images of the new
satellite when it flew by Uranus in late January, 1986. These images
have been publicly available in digital format. However, nobody
recognized the satellite until Karkoschka investigated these images
recently. He has studied the Uranian satellites based on images taken
with the NASA/European Space Agency Hubble Space Telescope (HST) and
found the new satellite when he compared his HST results with images
taken by Voyager 2.

(The discovery image can be viewed from the links below. The second
link is a high resolution version.)

The image shows Uranus with its ring system and the 10 innermost
satellites. All but S/1986 U 10 were known at the time the image was
taken, based on Voyager images taken in January 1986. Arrows at the
edge of the image point to the 10 satellites. The other dots of light
are background stars of the constellation Sagittarius. (If you know
enough astronomy to want to look this up on a star chart, the bright
star next to Juliet is Kaus Borealis, Lambda Sagittarii.)

Belinda and S/1986 U 10, imaged near the upper right hand corner,
circle Uranus in almost identical orbits. They pass each other once a
month. This is the first example of two satellites in nearby orbits
passing each other so slowly.

Astronomers began discovering moons around other planets in our solar
system in the 17th century. Throughout the approximately 60 satellite
discoveries made over the four centuries since, either Jupiter or
Saturn has had the most known satellites. Saturn is known to have 18
moons. Jupiter has 16 known satellites, not counting the Galileo
spacecraft, an artificial satellite around that planet. Many scientists
had thought that these two largest planets in our solar system would
have more moons than smaller planets. Smaller Uranus now dispells that
belief.

The other known satellites orbit Neptune (8 satellites), Mars (2
satellites), and Earth, Pluto, and asteroids Ida and Eugenia (1 each).

Soon after England's William Herschel discovered Uranus in 1781, he
found its two largest satellites, which are about half the size of our
moon. In 1851, English astronomer William Lassell detected two more
Uranian satellites. In 1951, Gerard Kuiper of the University of Chicago
-- later founder of the UA Lunar and Planetary Lab -- discovered
Uranus' fifth satellite. The Voyager team found 10 more Uranian
satellites in 1985-86.

Two years ago, Philip Nicholson of Cornell University discovered the
16th and 17th satellites. These two satellites are some 100 times
farther away from Uranus than are the satellites discovered by the
Voyager team.

Nicholson and Karkoschka have been the only scientists to find new
moons around a major planet in the 1990s. However, during this decade,
the first two satellites of minor planets (Ida and Eugenia) were
imaged.

The new satellite is about 25 miles (40 km) in diameter, similar in
size to comet Hale-Bopp, and it may also have similar composition as
the comet, Karkoschka said.

"Hale-Bopp was a spectacular sight when it crossed the inner part of
the solar system two years ago," he said. "On the other hand, the new
satellite will never get spectacular since it will remain in the dark,
frigid parts of the solar system. It will remain a tiny speck of
light."

Uranus may well have more than 18 satellites, Karkoschka noted: Jupiter
and Saturn have satellites of about half the size of the new Uranian
satellite. No such small satellite has yet been discovered around
Uranus since the dim sunlight at Uranus makes the detection of such
small satellites very hard.

Based on the detection in seven images, Karkoschka concluded that the
satellite orbits Uranus once every 15 hours and 18 minutes. This is
similar to the rotation period of Uranus. The satellite hovers 32,000
miles (51,000 km) above the clouds of Uranus, or the same distance as
the diameter of Uranus. The motions of satellites of Uranus can be
viewed at the Space Telescope Science Institute from the link below.

When Voyager 2 took the discovery image on January 23, 1986, it was
650,000 miles (1 million km) from Uranus. This is 2,500 times closer
than the Earth ever gets to Uranus. Nineteen hours later, Voyager 2
flew by Uranus.

The 10 satellites shown in the new discovery picture have been in
continuous sunlight during the last 25 years. Starting next year,
Cordelia, the satellite inside the ring system, will enter the shadow
of Uranus during every orbit. The other satellites will follow. By
2002, all 10 innermost moons will enter the shadow of Uranus every
orbit. These eclipses occur during two intervals within the 84-year
long Uranus-year. Similarly, lunar eclipses on Earth occur twice within
each Earth-year, currently in January and July.

The new discovery image is a mosaic of 10 exposures, Karkoschka said.
The exposures of Uranus had shorter exposure times than the exposures
of the surrounding area containing the rings and satellites. Since
Uranus is a million times brighter than its satellites, Karkoschka
retained the darker planet image so the satellites would be visible.

"To an astronaut on board the Voyager spacecraft, the satellites would
have appeared as faint stars while Uranus in the center would have been
blazingly bright, as bright as the full moon on Earth," Karkoschka
said. "In visible light, Uranus seems to be a bland, quiet place. Only
two faint little cloud features can be found upon close examination of
the image. The true activity in the atmosphere of Uranus is only
revealed in infrared light." While the Voyager camera was not sensitive
to infrared light, the Hubble Space Telescope has imaged atmospheric
activity. The HST image can be viewed from the link below.

The colors in the image are close to realistic, he added. The newly
discovered moon won't be stuck with the name "S/1986U10" forever,
Karkoschka noted. The International Astronomical Union names satellites
and asteroids a year or more after discovery. In the past, the IAU has
often adopted a name suggested by the discoverer if that name fits in
the context of the system's previously named satellites. However,
anyone can suggest what the new moon might be named, Karkoschka added.

Brush up your Shakespeare. Uranus' other nine innermost moons are
Belinda, Bianca, Juliet, Rosalind, Ophelia, Cressida, Portia, Cordelia
and Desdemona.

LINKS:
http://science.opi.arizona.edu/pics/disc1.jpg
http://science.opi.arizona.edu/pics/disc2.jpg
http://oposite.stsci.edu/pubinfo/pr/1999/11/animations.html
http://oposite.stsci.edu/pubinfo/pr/1998/35/index.html

----------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
----------------------------------------
The CCNet is a scholarly electronic network. To subscribe/unsubscribe,
please contact the moderator Benny J Peiser <b.j.peiser@livjm.ac.uk>.
Information circulated on this network is for scholarly and
educational use only. The attached information may not be copied or
reproduced for any other purposes without prior permission of the
copyright holders. The fully indexed archive of the CCNet, from
February 1997 on, can be found at http://abob.libs.uga.edu/bobk/cccmenu.html



CCCMENU CCC for 1999

The content and opinions expressed on this Web page do not necessarily reflect the views of nor are they endorsed by the University of

The content and opinions expressed on this Web page do not necessarily reflect the views of nor are they endorsed by the University of Georgia or the University System of Georgia.