--------------------------------------   
               |                                    |   
               |         Biuletyn PTA nr 18         |   
               |                                    |   
               --------------------------------------   
   
  Biuletyn informacyjny Zarzadu Glownego Polskiego Towarzystwa Astro-   
  nomicznego (Adres kontaktowy: M. Ostrowski, pta@oa.uj.edu.pl ,  
  a w bardzo pilnych sprawach: mio@oa.uj.edu.pl )   
=======================================================================   
   
Spis tresci:   
   
   I.   Wstepny program Zjazdu PTA we wrzesniu 2001

   II.  Nowosci naukowe - nie wszystkie calkiem nowe 
 
=======================================================================   

I. Wstepna informacja o Zjezdzie PTA w Krakowie

Najblizszy zjazd PTA odbedzie sie w Krakowie, w Instytucie Badan 
Polonijnych UJ^*, w okresie 10 - 12 (13) wrzesnia 2001. Ponizej 
przedstawiono wstepna przymiarke do "rozkladu zajec" w trakcie
Zjazdu. Wszyscy wykladowcy wyrazili zgode na wygloszenie wykladu,
ale ich tytuly i czas moga w niektorych przypadkach ulec zmianie.  

Zarzad PTA bardzo prosi wszystkich czlonkow o wlaczenie udzialu 
w Zjezdzie w swoj kalendarz konferencji. Na Walnym Zgromadzeniu 
pragniemy w koncu doprowadzic do przeglosowania nowego statutu PTA.

----------------------------------------------------------------------
Poniedzialek 
10.09    10:00-13:00    LKO          Rejestracja, kwaterowanie
 
         15:00                   Otwarcie Zjazdu
         15:30   B. Paczynski    Monitorowanie zmiennosci calego nieba
         16:30                   Przerwa
         17:00   T. Kwiatkowski  Badania fizyczne planetoid
                                  200 lat po ich odkryciu
         18:00   K. Stepien      Spotkanie z reprezentantem w KBN
 
         20:00                   Spotkanie powitalne
-------------------------------------------------------------------------
Wtorek 
11.09    09:00   R. Wielebinski  Radiowe mapy nieba
         10:00   J. Kaluzny      Stare oraz młode gromady kuliste
         11:00                   Przerwa
         11:30   G. Madejski     Zrodla rentgenowskie
         12:30
 
         15:00   J. Gil          Zagadka promieniowania radiowego pulsarow
         16:00                   Przerwa
         16:15     ------        Walne Zebranie
         18:15
         18:30     ------        Spotkanie dyr. inst i przedst. w KBN
 
         20:00     ------        Przyjecie konferencyjne
--------------------------------------------------------------------------
Sroda 
12.09    09:00   M. Tomczak      Promieniowanie rentgenowskie
                                 rozblyskow slonecznych
         10:00   R. Juszkiewicz  Kosmologia
         11:00                   Przerwa
         11:30   J. Kreiner      Sesja dydaktyczna
         13:00
 
         14:30   M. Abramowicz   Klasyczna i kwantowa fizyka czarnych dziur
         15:30   A. Zdziarski    Sesja instrumentalna
         17:30

         19:00                   Teatr, koncert (?) 
-------------------------------------------------------------------------- 
Czwartek
13.09       - Wycieczka szlakiem zegarow slonecznych (J. Kreiner)
---------------------------------------------------------------------------

^* Miejsce Zjazdu znajduje sie na lesistych wzgorzach nad Wisla, niedaleko
   krakowskiego ZOO i Obserwatorium Astronomicznego UJ. Zakwaterowanie 
   mamy zapewnione w hotelu Instytutu Badan Polonijnych, a wyzywienie
   w restauracji "U Zijada" 150 m obok. Zarzad PTA i LOK (przewodniczacy 
   M. Urbanik) czynia starania, aby uzyskac fundusze na dofinansowanie
   kosztow konferencji dla wszystkich, ktorzy bede tego potrzebowali. 
  
From: Marek Urbanik <urb@oa.uj.edu.pl>
Informacja od M. Urbanika rozbudowana przez M. Ostrowskiego. 

=======================================================================   

II.  Nowosci naukowe - nie wszystkie calkiem nowe 

STRANGE HALO ORBITS EXPECTED AT SATURN.  Consider
particles in orbit above a planet.  If the particles are uncharged or have a
very low charge-to-mass ratio, they will follow a conventional
("Keplerian") trajectory centered about the axis of the planet at the equator
(Saturn's rings are an example of such particles).  If, however, the
particles are highly charged, their motions are dominated by an
electromagnetic interaction with the planet's magnetic dipole (Earth's van
Allen belts are an example).  If the charge is somewhere in between these
two cases, and gravity and electromagnetic forces are comparable, then
strange orbits are possible.  Scientists at the University of Colorado
(Mihaly Horanyi and Jim Howard, 303-492-6903) and Loughborough
University (Holger Dullin) in the UK estimate that if conditions are just
right some particles could race around a planet in orbits (stable for as long
as 10 years) that never cross the planet's equatorial plane (see figure at
www.aip.org/physnews/graphics).  The dust analyzer on the Cassini craft
now gliding toward Saturn might be able to detect particles in these novel
orbits.  (Howard et al., upcoming article in Physical Review Letters;
Select Article.)

BEST MEASUREMENT OF THE GRAVITATIONAL
CONSTANT.  At this week's American Physical Society Meeting in
Long Beach, Jens H. Gundlach of the University of Washington
(paper P11.3) reported a long-awaited higher precision measurement
of the gravitational constant, usually denoted by the letter G. 
Although G has been of fundamental importance to physics and
astronomy ever since it was introduced by Isaac Newton in the
seventeenth century (the gravitational force between two objects
equals G times the masses of the two objects and divided by their
distance apart squared), it has been relatively hard to measure,
owing to the weakness of gravity.  Now a group at the University of
Washington has reduced the uncertainty in the value of G by almost
a factor of ten.  Their preliminary value is G=6.67390 x 10^-11 
m^3/kg/s^2 with an uncertainty of 0.0014%. Combining this new
value of G with measurements made with the Lageos satellite
(which uses laser ranging to keep track of its orbital position to
within a millimeter) permits the calculation of a brand new, highest
precision mass for the earth: 5.97223 (+/- .00008) x 10^24 kg. 
Similarly the new mass of the sun becomes 1.98843 (+/- .00003) x
10^30 kg. Gundlach's (206-543-4080, jens@phys.washington.edu)
setup is not unlike Cavendish's venerable torsion balance of two
hundred years ago: a hanging pendulum is obliged to twist under the
influence of some nearby test weights.  But in the Washington
experiment measurement uncertainties are greatly reduced by using
a feedback mechanism to move the test weights, keeping pendulum
twisting to a minimum.  (See Gundlach's written summary at
http://www.aps.org/meet/APR00/baps/vpr/layp11-03.html; figures at
www.aip.org/physnews/graphics.)

MAGNETIC FIELDS ARE EVERYWHERE.  The history of the
universe is usually described in terms of the distribution of matter:
first primordial knots, then clouds, galaxies, stars, and clusters.  A
parallel, and perhaps not unrelated, saga can be written for magnetic
fields. Basically, Philipp Kronberg (416-978-4971) of the University
of Toronto finds magnetic fields every place he has looked in the
cosmos: within the Milky Way (where the fields are typically about
5 microgauss), in intergalactic areas within galaxy clusters (1-2
microgauss for the Coma cluster, 350 million light years away), and
even outside clusters.  The latter observations are brand new and
were reported by Kronberg at the APS meeting
(http://www.aps.org/meet/APR00/baps/vpr/layb7-02.html). 
Detecting weak magnetic fields outside clusters was difficult and
required the use of new low-frequency receivers mounted on the
Very Large Array (VLA) radio telescope.  The radio range
employed, around 75 MHZ, is normally problematic owing to
scattering in the Earth's ionosphere, but new image processing
techniques have allowed a sharp VLA "deep field" image to be
formed.  From the intensity of the radio glow, Kronberg deduced a
magnetic field of about 10^-8 to 10^-7 gauss for a distant region
outside any galaxy cluster, a place (near the "Great Wall") where
fields had not been mapped before.  Where did such fields come
from?  Kronberg suggests that huge shock waves, formed where two
large streams of weakly magnetized gas come together, could
amplify existing fields to much higher levels, as well as playing a
part in the acceleration of cosmic rays.  Angela Olinto (paper B7.1)
of the University of Chicago (773-702-8206) discussed the idea of
primordial magnetism, fields that might have existed at or shortly
after the time of the big bang.  Such fields, she speculated, might
have come about through the development of some asymmetry (just
as matter came to predominate over antimatter) in the infant
universe.  Early magnetism might  then have influenced subsequent
galaxy formation or even the distribution of matter now seen
imprinted in the cosmic microwave background (CMB).  She said
that the surprising absence of subsidiary peaks in the CMB spectrum
(see Update 481) might be attributable to magnetic effects.  This
hypothesis could be addressed, Olinto said, by the Planck satellite
(launch date several years from now; see Update 342), dedicated to
mapping the CMB with unprecedented precision.

GRAVITY HAS BEEN MEASURED AT THE SUB-
MILLIMETER SCALE for the first time.  Gravity has of course
long been studied over planetary distances but is more difficult to
gauge at the terrestrial scale, where intrusive electric and magnetic
fields, many orders of magnitude stronger than gravity fields, can be
overwhelming.  Nevertheless, Eric Adelberger and his colleagues at
the University of Washington have managed to measure the force of
gravity over distances as small as 150 microns using a disk-shaped
pendulum carefully suspended above another disk, with a copper
membrane stretched between them to help isolate electrical forces.
(This experiment should not be confused with another University of
Washington effort in which the gravitational constant is measured
with higher precision see Update 482).   Adelberger (206-543-
4294, eric@gluon.npl.washington.edu) presented one of several
talks at this week's APS meeting in Long Beach, California devoted
to short-range gravity, a subject which has suddenly attracted much
theoretical and experimental interest owing to a relatively new
model which supposes the existence of extra spatial dimensions in
which gravity, but not other forces, might be operating.  According
to Nima Arkani-Hamed of LBL (arkani@thsrv.lbl.gov, 510-486-
4665) this is why gravity is so weak: it dilutes itself in the extra
dimensions. In other words, ordinary particles are tethered to our
conventional spacetime, or "brane," while gravitons are free to roam
into otherwise unseeable dimensions.  One implication of the model,
testable with tabletop experiments such as Adelberger's, is that the
gravitational force might depart from Newton's inverse square law
(gravity inversely proportional to the square of the distance between
two objects) at close range. Adelberger did not observe such a
departure at distances down to tenths of a millimeter and will
continue to explore even shorter distances.  For a list of tabletop
experiments underway, see
http://gravity.phys.psu.edu/mog/mog15/node12.html.
     Another interesting implication of  the model introduced by
Arkani-Hamed (and others; see preprint hep-th 9803315) two years
ago is that the unification of the four known forces would not
necessarily occur at energies as high as 10^19 GeV but possibly at
energies as low as 10^4 GeV, an energy scale within reach of the
Large Hadron Collider under construction at CERN.  Extra
dimensions could, for example, manifest themselves in proton-
proton smashups as an apparent disappearance of energy, implying
that some of the collision energy had been converted into gravitons
(the particle form of gravity) which then disappear into the extra
dimensions.  The gravitons produced in this way might come back
into our conventional world of 3 spatial dimensions and decay into
two photons.  Physicists have already looked for this kind of event. 
Gregory Landsberg of Brown University (401-863-1464;
landsberg@hep.brown.edu) reported that at the D0 experiment at
Fermilab some energetic two-photon events have been observed
(including one in which the energy of the photons added up to 574
GeV, representing the highest composite mass ever seen in the D0
experiment) but not often enough to constitute evidence for extra
dimensions.  In fact this shortage of events has been translated into a
lower limit of 1300 GeV for the energy at which a prospective
unification of the forces could take place.

THE FIRST GLOBAL IMAGE OF THE EARTH'S
PLASMASPHERE, the shell of positively charged ions and
negatively charged electrons lying at the top of our atmosphere and
extending far out into space, has been recorded by the Imager for
Magnetosphere to Aurora Global Exploration (IMAGE) satellite. 
The ability to view the Earth and its environs through plasma-
colored glasses is important for understanding basic geophysics
properties of the Earth and for monitoring "space weather," the
general name for disturbances in our planet's vicinity caused by
fields and particles coming from the sun.  A violent storm on the
sun can, a few days later, pose hazards for satellites and even
ground-based power grids.  IMAGE performs its sentry duty by
photographing the glow caused when light or particles coming
directly from the sun or nearby particles whipped up to high
energies smash into atoms in our upper atmosphere.   Launched in
March 2000, the IMAGE spacecraft follows a highly eccentric
orbit which takes it far enough from the Earth that at times the
whole planet, and its fluorescing plasma, can be captured within
the photographic frame.  First data from the IMAGE mission were
reported this week by James Burch, Southwest Research Institute
(210-522-2526) and several colleagues at the American
Geophysical Union meeting in Washington, DC.   One surprise: a
picture of the helium glow around  the Earth at extreme ultraviolet
(EUV) wavelengths (see figure at
www.aip.org/physnews/graphics) exhibited unexplained lobe
structures. Another first: separate ultraviolet movies of electron
and proton auroras were shot simultaneously by using filters that
discriminate among fluorescence at different wavelengths coming
from hydrogen, oxygen, and nitrogen atoms in the atmosphere;
EUV at 121 nm, for instance, comes from energetic protons
resonantly scattering from hydrogen atoms.  To locate more
precisely the position and velocity of the plasma clouds being
viewed, IMAGE uses an immense cross-shaped radio antenna
(mission scientist James Green of Goddard Space Flight Center
called it a "radar cop in the sky") measuring 500 meters from tip to
tip (longer than the Empire State Building is tall, or equivalent to
three Washington Monuments laid end to end), making it the
longest manmade structure in space.  (See also the IMAGE
website: http://image.gsfc.nasa.gov/press_release/2000_05_31/.)

JUPITER'S MOON IO BEARS WATCHING.  The most
volcanically active object in the solar system, Io has recently been
visited again (in Feb 2000) by the Galileo spacecraft, and the
surface shows noticeable changes from a flyby made in Oct 1999.
Results reported at last week's American Geophysical Union
meeting in Washington, DC include the following:  John Spencer of
the Lowell Observatory summarized infrared observations of Loki,
Io's (and the solar system's) greatest volcano, whose immense lava
flow, the size of Connecticut, is unequaled on Earth in historic
times.  In the past few months the flow has warmed by 40 K and
greatly grown.  Rosaly Lopes-Gautier of JPL showed several new
hot spots (potential volcanos) discovered with a high-resolution
infrared spectrometer.  One might extrapolate from the density of
sources, she said, that Io might have more than 300 volcanos,
representing a colossal energy loss.  Meanwhile, Alfred McEwen of
the University of Arizona described the Chaac canyon which, with a
depth of 2.8 km and an average steepness of 70 degrees, is much
more dramatic than the Grand Canyon in Arizona (1.5 km deep and
30 degrees in steepness).  See also Science, 19 May 2000.


THE NEXT GENERATION SPACE TELESCOPE (NGST), 100
times more sensitive than the Hubble Space Telescope, sits at the
top of the list of desirable future observatories, a list formulated by
the National Academy of Sciences.  The billion-dollar NGST
should possess an 8-m mirror, an orbit 1 million miles from Earth,
and an ability to view the most distant (and earliest) stellar objects
in the universe at infrared wavelengths.  Next in order of priority is
the Giant Segmented Mirror Telescope (GSMT), a 30-m ground
based telescope for complementing with superb spectroscopy the
sharp imaging of the NGST; the $800 million Constellation-X
Observatory, specializing in x rays; an Expanded Very Large
Array (EVLA) radio telescope; the Large-aperture Synoptic
Survey Telescope (LSST), which would scan the whole sky, every
week for faint objects; and the Terrestrial Planet Finder (TPF), "the
most ambitious science mission ever attempted by NASA," whose
goal is to search for planets around nearby stars.  (NAS website:
http://www.nationalacademies.org/topnews/.)


NEW MEASUREMENTS OF DEUTERIUM at the center of our
Milky Way galaxy confirm theoretical models that most deuterium,
the heavy isotope of hydrogen containing one proton and one neutron,
is primordial (made at the time of the big bang) and not subsequently
created in galaxies or stars.  A Hofstra-Williams-Colgate-Manchester
(UK) team of astronomers have used the National Radio Astronomy
Observatory 12-m radio telescope to scan a huge molecular cloud only 
30 light years from the galactic center.  In particular they look at the
spectra of hydrogen cyanide (HCN) and its deuterium counterpart
DCN.  In general stars are expected to be net consumers (not
producers) of deuterium: they burn it into helium.  But the galactic
center is the Times Square of the Milky Way; it is the scene of jets,
bursts, x-ray and gamma sources, a massive black hole, filaments,
arcs, and other material-processing objects.   From their observed ratio
of deuterium-to-hydrogen  D/H, the researchers (Don Lubowich, Jay
Pasachoff, Tom  Balonek, and Tom Millar) deduce three things:  (1)
The D/H ratio is higher than you would expect in the absence of a
source of  virginal unprocessed material  (high in  D,  low in heavier
elements).  This demonstrates that matter comparatively rich in D is
indeed raining down with the cloud onto the plane of our galaxy (see
figure at www.aip.org/physnews/graphics).  In other words, the
infalling matter is to the galaxy what comets are to our solar system:
specimens of relatively unprocessed, primitive material.  (2)  For all
that, the D/H ratio at the galactic center is lower than in all other
places in the galaxy.  This is important evidence confirming that D is
not made in stars and that what D we see is made by the big bang.  (3) 
>From models of D production in quasars, the observed D/H ratio
suggests that the Milky Way could not have harbored a quasar for at
least a billion years and probably not for four billion years. 
(Lubowich et al., Nature, 29 June 2000.)

MARTIAN GULLIES, perhaps as young as thousands of years old or
even newer, have been photographed by the orbiting Mars Global
Surveyor.  Evidence of ancient water action on the Martian surface
had been noted before, but the sharper resolving power of the Global
Surveyor shows that the water-cut features lie on top of older
rockforms.  The presence of recent, not just ancient, water flows will
certainly enter into discussions of the hypothetical existence and
nature of Martian life.  (NASA press release, 22 June; also Science, 29
June 2000.)  Meanwhile, the density of tiny water crystals in a
Martian meteorite recovered in Antarctica (a rock jarred loose from
Mars perhaps 3 million years ago) indicates that Mars might have a
below-surface reservoir of water two to three times higher than
previously thought.  (Laurie Leshin of Arizona State, reporting in the
15 July Geophysical Research Letters.)

A PLANETESIMAL AGGREGATION EXPERIMENT has been
carried out in the low gravity environment of the Space Shuttle to test
notions of how our solar system developed from a primordial cloud
of micron sized dust particles.  The experiment is the first direct re-
creation, under realistic solar-nebula conditions, of the proposition
that protoplanetary dust accumulates through sticky collisions amid
the random Brownian motion of the particles.   A consortium of
German and US scientists (contact Jurgen Blum, University of Jena,
Germany, 011-49-364-194-7515, blum@astro.uni-jena.de) observed
that the dust quickly aggregates.  The data bears out the main theory
of planetesimal formation, but there was one surprise: the structures
were expected to be somewhat fractal in nature, with a fractal
dimension d of about 1.8, meaning that the mass of the cluster should
be proportional to the cluster size raised to the d power.  Instead the
dimensionality turned out to be about 1.3, meaning the structures
were observed to be more linear and less sheetlike (see figure at
www.aip.org/physnews/graphics).  (Blum et al., Physical Review
Letters, 18 September 2000; Select Article.)           

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