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Human in the Mouse Mirror
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data support MACHOs
the January meeting of the American Astronomical Society in San
Diego, California, Livermore's Kem Cook and Cailin Nelson—reporting
on behalf of the 14-organization collaboration to detect and study
Massive Compact Halo Objects (MACHOs)—presented evidence of microlensing
events caused by MACHOs in the halo of the Milky Way. Microlensing
is a physical phenomenon that causes a star to appear to shift or
brighten when it lies on the same line of sight as another star.
The phenomenon is a way to detect MACHOs, which emit light below
current detection thresholds and must therefore be discovered by
other means. In MACHO microlensing, the MACHO passes through an
observer's line of sight to an ordinary, luminous star. The MACHO's
gravitational presence causes the light from the ordinary star to
bend and also temporarily increase in brightness. That brightened
star is called a source star.
MACHO project has been monitoring the sky with the 1.27-meter telescope
at Mount Stromlo Observatory in Australia to detect microlensing
events in a line of sight toward our neighboring Large Magellanic
Cloud galaxy, which provides a convenient backdrop of source stars.
When the microlensing events were detected, some astronomers speculated
that it was not MACHOs, but the faint stars in the Large Magellanic
Cloud that were lensing other stars. If MACHOs are the cause of
the microlensing, the source stars would be randomly distributed
in the Large Magellanic Cloud, but if the source stars were found
toward the far side of that galaxy, then the Large Magellanic Cloud
would likely be the cause of microlensing.
determine the cause of microlensing, the project collaborators turned
to Hubble Space Telescope data on the area surrounding each microlensing
event. Using the technique of difference image analysis, they were
able to identify the source star of each microlensing event and
therefore determine the arrangement of the source stars. The team
found no evidence that the source stars are not randomly distributed
in the Large Magellanic Cloud.
Contact: Kem Cook (925) 423-4634 (firstname.lastname@example.org).
150 high-proper-motion stars discovered
at the January meeting of the American Astronomical Association,
astronomer Andrew Drake presented results from studying fifty thousand
astronomical images of fifty-five million stars made by the Great
Melbourne Telescope in Canberra, Australia, over a 7-year period.
The telescope had been used during the 1990s to detect the gravitational
microlensing of stars.
reported finding 154 rapidly moving stars—called high-proper-motion
(HPM) stars—toward the center of our galaxy and that of our brightest
neighbor, the Large Magellanic Cloud. This finding is of special
interest because it is the first time that scientists have been
able to discover HPMs in front of the stars seen at our galactic
center, which is packed so densely with stars that images of the
stars seem merged, or in the Large Magellanic Cloud, which appears
as a faint nebulous patch in the sky.
find the HPMs, Drake identified the stars that appear to move and
measured their motions. The yearly motions of these objects are
estimated to be accurate to 6 milliarcseconds, which is equivalent
to the width of a human hair seen from the distance of a mile. Drake's
measurements led to the discovery of the HPMs.
astrometry, a branch of astronomy that deals with the measurement
of positions and movements and has produced a picture of the motions
of stars within our galaxy, Drake was able to predict that most
of his discovered HPM stars are between 100 and 1,000 light years
away. These measurements, however, are preliminary, and more studies
are needed to gather details about the HPM stars.
Contact: Andrew Drake (925) 424-6781 (email@example.com).
in war against chemical weapons
the behest of the U.S. State Department, Lawrence Livermore, home
to the Forensic Science Center, has begun the procedure to become
certified by the Organization for the Prohibition of Chemical Weapons
(OPCW). The organization implements the Chemical Weapons Convention
ratified by over 135 countries to outlaw chemical weapons and the
transfer of chemical-weapon-related technologies. As an accredited
laboratory, Livermore would participate in testing chemical samples
from around the world to determine whether samples contain chemical
weapons agents, their precursor chemicals, or their decomposition
the terms of the Convention, all chemical samples must be tested
at two OPCW-designated laboratories. Congress mandates that all
U.S. samples must be tested in the U.S. Currently, the nation has
one designated laboratory, the Edgewood Chemical and Biological
Forensic Analytical Center in Maryland. Livermore would become the
second laboratory required for this testing.
Richardson, deputy program leader for the Proliferation Prevention
and Arms Control Program, says that this work is "one more way the
Laboratory can contribute to national and international security."
Richardsons stresses that the samples for testing will "be extremely
dilute (that is, on the part-per-million level). So dilute that
they can be shipped commercially or sent through the mail." One
of the reasons the Laboratory was selected for this work is its
ability to characterize chemicals at ultratrace levels.
Contact: Jeff Richardson (925) 423-5187 (firstname.lastname@example.org).
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