🚀 go-pugleaf

**********************************************************************

This is a "Physics News Update" distributed by Phillip Schewe of AIP
Public Information.  For those who want to receive PNUPs via email,
mail pfs2@aip.org with your address and you will be added to the
distribution list.

I am redistributing this with Mr. Schewe's permission.  Complaints or
suggestions about the Updates should go to him at pfs@aip.org.

Sendhil Revuluri (s-revuluri@uchicago.edu)
University of Chicago

**********************************************************************

PHYSICS NEWS UPDATE
A digest of physics news items prepared by Phillip F. Schewe, AIP
Public Information
Number 102   November 10, 1992

CRYSTALLIZED STARS.  Scientists have previously thought that
as white dwarf stars assumed their final repose, a wave of
crystallization would propagate outward from the interior, freezing
nuclei into a lattice.  Gilles Chabrier (Ecole Normale Superieure
de Lyon, France), Neal W. Ashcroft (Cornell), and Hugh E.
DeWitt (Livermore) believe that such an ensemble of particles
cannot be treated classically (as was the case) but must be
considered as a quantum liquid freezing into a quantum solid. 
The result of their re-evaluation would be to lower the freezing
temperature of heavier white dwarfs and to slow their cooling and
evolution.  This in turn would have implications for studies of the
galactic disk and halo.  (Nature, 5 Nov. 1992.)

DID A METEOR KILL THE DINOSAURS?  A new study
provides additional support for the idea that a buried impact basin
on the Yucatan peninsula was the site of an impact that was fatal
to many life forms at the (KT) boundary between the Cretaceous
and Tertiary periods 65 million years ago.  Scientists from the
Lunar and Planetary Institute (Houston), the U.S. Geological
Survey (Menlo Park, CA), and Geophysical Institute (Mexico City)
report new studies of melted rock, showing that the levels of
iridium and the ratios of argon isotopes at the Yucatan crater
agree with those of KT samples from around the world.  (Nature,
29 Oct. 1992.)  In contrast, other scientists, such as Charles Officer
of Dartmouth, continue to assert that an impact may not have
been the culprit and that instead certain artifacts, such as
anomalous iridium, could be produced in volcanic eruptions. 
(Science News, 7 Nov. 1992.)

SUPERMASSIVE BLACK HOLES probably exist, but
astronomers won't be convinced merely by the impressive increase
in luminosity of starlight toward the center of certain galaxies.  
According to Alan Dressler of the Carnegie Institution, conclusive
evidence for black holes would come from the spectroscopic study
of the movement of stars in the vicinity of the hole.  The necessary
high resolution may come with a rejuvenated Hubble Space
Telescope or with the new optical telescopes being built atop
Mauna Kea.  Based on preliminary studies of star motion, the
galaxies most likely to be harboring supermassive black holes are
Andromeda, its satellite galaxy M32, and NGC3115 (whose
candidate black hole would have a mass of more than a billion
solar masses).  In the long run, it may be easier to hunt for black
holes in relatively placid galaxies like these, where the lack of the
energy glare associated with active galaxies can only make easier
the task of viewing star motion near the galactic core.  As for our
own presumed resident black hole, studies of the Milky Way's
central precinct are hindered by viewing problem of another sort,
namely the presence of dust.  Nevertheless, indirect measurements
of star motion are consistent with the idea of a black hole at the
galactic core.  (Science News, 31 Oct. 1992.)

LARGE PARTICLE PHYSICS COLLABORATIONS, particularly
as they function as administrative and sociological organizations,
are the subject of a new report issued by AIP.  All the symptoms
that characterize big science are to be found here: increasing
paperwork, the importance of the national labs, mountains of data,
and PhD's ten years in the making, etc. (For more information
contact Joel Genuth at AIP: 212-661-9404.)

**********************************************************************

Sendhil Revuluri (s-revuluri@uchicago.edu)