PLEASE NOTE:
*
CCNet DIGEST, 12 April 1999
---------------------------
(1) LINK BETWEEN SOLAR CYCLE AND CLIMATE CHANGE
Andrew Yee <ayee@nova.astro.utoronto.ca>
(2) GIANT IMPACTS AND GLOBAL CLIMATE CHANGE ON VENUS
Michael Paine <mpaine@tpgi.com.au>
(3) ASTRONOMER WHO HELPED SAVE SPACECRAFT REWARDED WITH CELESTIAL
GIFT
Andrew Yee <ayee@nova.astro.utoronto.ca>
(4) ASTRONOMERS SOLVE THE CASE OF THE UNKNOWN STAR EXPLOSION
Andrew Yee <ayee@nova.astro.utoronto.ca>
(5) U.S. MISSILE WARNING SATELLITE IN WRONG ORIBIT
BBC Online Network, 12 April 1999
====================
(1) LINK BETWEEN SOLAR CYCLE AND CLIMATE CHANGE
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Lynn Chandler
Office of Public Affairs April 8, 1999
Goddard Space Flight Center
Greenbelt, Maryland 20771
Phone: 301-614-5562
RELEASE NO. 99-39
LINK BETWEEN SOLAR CYCLE AND CLIMATE IS BLOWIN' IN THE WIND
Researchers have found that the variations in the energy given
off from
the sun effect the Earth's wind patterns and thus the climate of
the
planet, according to results of a new study published in the
April 9 issue
of Science.
For decades, scientists have tried to understand the link between
winds
and temperature and the sun and its cycles. There were tell-tale
signs
of a connection. For instance, the Little Ice Age recorded in
Europe
between 1550 and 1700 happened during a time of very low solar
activity. But
how the sun and climate were linked continued to elude
researchers.
According to Drew Shindell, a climate researcher from NASA's
Goddard
Institute for Space Studies in New York, NY, and lead author of
the new
study, a key piece of the puzzle was missing. Previous studies
neglected
to take into account the effects of increased solar activity on
the
ozone layer or the complex chemistry of the upper atmosphere
where most of
the high-energy radiation, including ultra-violet radiation (the
kind
responsible for creating the ozone layer) gets absorbed.
"When we added the upper atmosphere's chemistry into our
climate model,
we found that during a solar maximum major climate changes occur
in
North America." The changes, according to Shindell, are
caused by
stronger westerly winds. Changes also occur in wind speeds and
directions
all over the Earth's surface.
"Solar variability changes the distribution of energy,"
said Shindell.
"Over an 11-year solar cycle, the total amount of energy has
not changed
very much. But where the energy goes changes as wind speeds and
directions
change." During the sun's 11-year cycle, from a solar
maximum to a solar
minimum, the energy released by the sun changes by only about a
tenth of a
percent.
When the solar cycle is at a maximum, it puts out a larger
percentage of
high-energy radiation, which increases the amount of ozone in the
upper
atmosphere. The increased ozone warms the upper atmosphere and
the warm air
affects winds all the way from the stratosphere (that region of
the
atmosphere that extends from about 6 to 30 miles high) to the
Earth's
surface. "The change in wind strength and direction creates
different
climate patterns around the globe," said Shindell.
According to Shindell, the new study also confirms that changing
levels
of energy from the sun are not a major cause of global warming.
Many scientists have argued that the radiation change in a solar
cycle
- an increase of two to three tenths of a percent over the 20th
century -
are not strong enough to account for the observed surface
temperature
increases. The GISS model agrees that the solar increases do not
have
the ability to cause large global temperature increases, leading
Shindell
to conclude that greenhouse gasses are indeed playing the
dominant role.
The general circulation model used in the study included solar
radiation
data from NASA's Upper Atmospheric Research Satellite, launched
in
1991. With data from UARS, which was used to calculate ozone
changes,
scientists have good measurements of how much radiation the sun
puts
out, increasing the accuracy of the new model.
==============
(2) GIANT IMPACTS AND GLOBAL CLIMATE CHANGE ON VENUS
From Michael Paine <mpaine@tpgi.com.au>
"Global climate change on Venus" by Mark A. Bullock and
David H.
Grinspoon [Scientific American, March 1999] describes evidence of
"a
geological event of global proportions [that] wiped out all the
old
craters some 800 million years ago". The article notes that
"the idea of
paving over an entire planet is unpalatable to many
geologists" and
explanations such as planet-wide volcanism are discussed. There
is,
however, an event that could result in the entire surface of a
planet
being "repaved" - an impact by a comet hundreds of
kilometres in
diameter. I understand that this would not necessarily cause a
recognizable impact "crater" but could severely disrupt
the crust and
trigger volcanism. Research into this possibility would need to
explain
how Venus subsequently acquired its very dense atmosphere, since
the
original atmosphere would have been stripped away, and what
happened to
the impact debris in space - why didn't a small moon or ring
form?
Perhaps 800 million years is sufficient time for Venus to
"recover".
Michael Paine
The Planetary Society Australian Volunteers
============
(3) ASTRONOMER WHO HELPED SAVE SPACECRAFT REWARDED WITH CELESTIAL
GIFT
From Andrew Yee <ayee@nova.astro.utoronto.ca>
News Service
Cornell University
Hero astronomer who helped save spacecraft rewarded with
celestial gift
Contact: Blaine P. Friedlander, Jr.
Office: (607) 255-3290
E-Mail: bpf2@cornell.edu
FOR RELEASE: April 9, 1999
ITHACA, N.Y. -- A Cornell University astronomer who helped save a
$150
million space mission last December was rewarded at a surprise
party
this afternoon with a truly heavenly gift: A minor planet named
in her
honor.
The International Astronomical Union (IAU), the world's authority
on
celestial nomenclature, announced that minor planet 4896 P-L now
will be
known as Asteroid 9251 Harch. It is named for Ann P. Harch, a
research
specialist at Cornell's Center for Radiophysics and Space
Research,
whose efforts helped save the Near Earth Asteroid Rendezvous
(NEAR)
spacecraft mission.
"You guys are bad! You guys are bad!" said Harch after
she was told the
news at the party at Cornell's Space Sciences Building.
"I've worked really
hard on those asteroid flybys. It's really nice when your
colleagues
recognize you."
The NEAR spacecraft seemed to be doomed after contact was lost
Dec. 20,
just days prior to its flyby of the asteroid 433 Eros, about 240
million
miles from Earth. But after contact was renewed, scientists
quickly
formulated a new mission plan, largely due to Harch's ingenuity,
as well
as that of researchers at Cornell, NASA's Jet Propulsion
Laboratory
(JPL) in Pasadena, Calif., and Johns Hopkins University's Applied
Physics
Laboratory (APL) in Laurel, Md. As a result, signals were sent in
the
nick of time, enabling the spacecraft to capture images as it
approached
Eros.
Donald Yeomans, an astronomer with the JPL, nominated Harch for
her
expertise in designing spacecraft camera sequencing and pointing
commands -- giving researchers the ability to take pictures of
asteroids
during spacecraft flybys. She played a major role in obtaining
the first
spacecraft images of asteroids 951 Gaspra and 243 Ida during the
Galileo
mission flybys in the early 1990s. Harch also was the first to
notice
evidence for Ida's moon, Dactyl. In June 1997, during the NEAR
mission,
Harch succeeded in imaging 253 Mathilde and got the last-minute
shots
of Eros last December.
Brian Marsden, director of the IAU's Minor Planet Center in
Cambridge,
Mass., says that 9251 Harch is among the 223 asteroids given
names last
week, the biggest batch in astronomical history. Researcher Harch
joins
about a half-dozen other Cornellians whose names have been
bestowed
on celestial bodies.
Asteroid 9251 Harch is some 236 million miles from the sun,
somewhere
between the planets Mars and Jupiter. It began as nothing more
than a
pinpoint on a photographic plate, captured by Tom Gehrels, an
astronomer
at the University of Arizona, on Sept. 26, 1960, during a sky
survey
using the 48-inch Schmidt telescope at the Palomar Observatory on
Mount
Palomar, Calif.
Gehrels shipped the plates from his survey to astronomers Kees
van
Houten and Ingrid van Houten-Groeneveld at the Leiden Observatory
in the
Netherlands. Scanning the plates, the Dutch astronomers
discovered about
2,400 asteroids -- often described as minor planets -- and
calculated
their general orbits. An asteroid, later dubbed 4896 P-L, was
among
them.
But confirmation of the asteroid's orbit did not come until
spring 1997,
when astronomers at the Massachusetts Institute of Technology's
Lincoln
Laboratory conducted a sky survey with a charge-coupled device
(CCD)-enhanced telescope and found an object temporarily named
1997 HK12,
according to Marsden. Gareth Williams, the associate director of
the Minor
Planet Center, then calculated that 1997 HK12 and 4896 P-L
were one and the same.
Astronomical tradition dictates that discoverers get first crack
at
naming a celestial object. But the Dutch astronomers, who had
discovered
thousands of asteroids, ran out of ideas and, says Marsden,
"threw up
their hands."
The IAU agreed to name hundreds of these objects. Yeomans served
on
the IAU naming committee and suggested names for six of the
asteroids.
Harch's was among them.
Related World Wide Web sites:
The following sites provide additional information on this news
release.
* Cornell Astronomy: http://astrosun.tn.cornell.edu/index.html
-30-
PHOTO CAPTION:
[http://www.news.cornell.edu/releases/April99/PlanetHarch.bpf.html]
Joseph Ververka, Cornell professor of astronomy and leader of
NEAR
imaging team, congratulates Ann Harch after she learned that an
asteroid had been named for her. (Cornell News Service
photo)
================
(4) ASTRONOMERS SOLVE THE CASE OF THE UNKNOWN STAR EXPLOSION
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Bill Steigerwald
Goddard Space Flight Center April 8, 1999
Greenbelt, MD 20771
William.A.Steigerwald.1@gsfc.nasa.gov
Phone: 301-286-5017
RELEASE NO: 99-37
ASTRONOMERS SOLVE THE CASE OF THE UNKNOWN STAR EXPLOSION,
DISCOVER RARE
COUPLING OF ELEMENTS
Astronomers have pieced together the scene of a crime that no one
saw: a
700-year-old star explosion nearly as bright as a full moon,
undocumented by early stargazers and unknown to modern-day
astronomers until
only very recently. Clues came in the form of two radioactive
elements never
before seen together in such explosions, a rare event that offers
a new
avenue to test star explosion theories.
Drs. Wan Chen and Neil Gehrels [Tom's son] at NASA's Goddard
Space Flight
Center, Greenbelt, Md., calculated the explosion source to most
likely be a
star 15-times more massive than the Sun and a mere 500
light-years away. The
star, the astronomers said, must have depleted its nuclear fuel,
experienced
a core collapse, and exploded.
While the fact that no one documented this explosion until last
year is
interesting in itself, Drs. Chen and Gehrels were intrigued to
find that
radioactive titanium and aluminum detected in the region came
from the
same source. Previously, astronomers assumed they could only see
one
element or the other in an explosion remnant.
"Different models of supernova explosions offer different
yields of
titanium, aluminum and other elements," said Dr. Chen.
"When we have one
source producing both titanium and aluminum emission, it provides
tighter calculation constraints, and we can pretty much figure
out what kind
of star exploded."
The astronomers' calculations were based on X-ray light from hot
gas in
the remnant and gamma rays produced by decaying titanium-44,
detected
in 1998. Gamma ray astronomers had known about decaying
aluminum-26
in the region as early as 1992 and assumed the emission came from
the
Vela supernova, an older and more powerful, more distant
explosion. Drs.
Chen and Gehrels' interpretation of the older data showed that
the
aluminum-26 most likely originated in the more recent explosion,
and
this supported their initial calculations.
Dr. Chen said no one ever observed radioactive decay from two
elements
together in the same star (supernova) explosion because the
elements'
half-lives (the time required for half the amount of an element
to
undergo radioactive decay to a new form) are so different. The
half-life of
titanium, for example, is 60 years; for aluminum, it is 700,000
years.
That means that after an explosion, decaying titanium is
plentiful, but
decaying aluminum is not. After about a thousand years, most of
the titanium
is gone. So to see both elements at the same time, the explosion
must be
close enough to Earth to detect the small traces of decaying
aluminum and
recent enough to detect decaying titanium before it vanishes.
"The rate for supernovae in the entire Galaxy is about one
in every 50
to 100 years," said Dr. Chen. "If 'close' means within
1,500 light-years
from Earth, then given the size of the Milky Way, we'll have to
wait about
20,000 years for the next close event."
The newly discovered explosion is now known as supernova remnant
GRO/RX
J0852. The source has shown astronomers that rare events do
exist, and
that other supernova remnants could harbor the remains of other
combinations
of radioactive elements, which could further bolster supernova
modeling.
Dr. Anatoli Lyudin of the Max Planck Institute of
Extraterrestrial
Physics led an international team in first observing titanium
emission from
GRO/RX J0852 region in 1998 with the COMPTEL gamma-ray telescope
on NASA's
Compton Gamma Ray Observatory. Dr. Bernd Aschenbach, also at Max
Planck,
first observed the remnant in X-rays with instruments aboard the
German-operated ROSAT satellite (a German/US/UK joint venture).
Drs. Chen
and Gehrels based their calculations on these data.
Astronomers had never noticed the elusive remnant because a
massive
fiery gas cloud behind it from yet another supernova explosion,
the
11,000-year-old Vela remnant known for centuries, overshadowed
it.
Observing the region in a higher X-ray energy band brought out
the
features of the younger explosion. Likewise, observing the region
in gamma
rays revealed only the radioactive titanium from GRO/RX J0852,
for Vela had
long since lost its titanium.
The supernova explosion was close enough within the Milky Way to
be seen
by medieval astronomers near or below the equator for months,
even
during daylight hours. Yet there is no written record of the
event. Dr. Chen
is collecting theories from other astronomers on why this
happened. These
theories include, among many, cultural upheaval in Central and
South
America, social unrest and war in China, or simply records lost
over
time.
"It's a real mystery," said Dr. Chen. "This
supernova was very bright.
People had to have seen it, but we haven't found any written
records
yet."
The results of Drs. Chen and Gehrels' work appear in the April 1
issue
of The Astronomical Journal and are presented at the April 15
meeting of
the High Energy Astrophysics Division of the American
Astronomical Society.
EDITOR'S NOTE: Images to support this story are available on the
web at:
FTP://PAO.GSFC.NASA.GOV/newsmedia/HEAD/SN
==============
(5) US MISSILE WARNING SATELLITE IN WRONG ORIBIT
From the BBC Online Network, 12 April 1999
http://news.bbc.co.uk/hi/english/sci/tech/newsid_316000/316520.stm
A US missile warning satellite launched by the troubled Titan
rocket
programme is in the wrong orbit, according to the US Air Force.
The $250m Defence Support Programme satellite went up without a
hitch
from Cape Canaveral on Friday on board the unmanned Titan 4B
rocket.
FULL STORY at
http://news.bbc.co.uk/hi/english/sci/tech/newsid_316000/316520.stm
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