Physics Update
PHYSICS UPDATE
The American Institute of Physics
Bulletin of Physics News
ULTRAHIGH ENERGY COSMIC RAYS, those with energies above 10**19 eV, pose a
problem for astrophysicists. The rays can't originate from too far out in the
cosmos, otherwise interactions with photons in the cosmic microwave background
would have cooled down the cosmic rays to lower energies. Do they, as some
theorists propose,come from the decay of superheavy primordial particles? (See
the item in New Scientist, 26 August 1995) Addressing the subject of whether
the high energy cosmic rays come from relatively nearby, a new study of the
arrival directions of 143 cosmic ray events with energies of higher than
2x10**19 eV reveals a nonuniformity; the rays seem to arrive preferentially
from the "supergalactic plane," which, according to Todor Stanev of the Bartol
Insitute (temporary address in Italy: stanev@roma1.infn.it) is defined by the
agglomeration of nearby galaxies (redshift less than 0.03); in the northern
hemisphere this wold mean roughly the Virgo cluster of galaxies. This finding
supports the notion that the highest energy cosmic rays originate outside our
own galaxy, perhaps in relatively neraby radio glaxies. (Todor Stanev et al.,
upcoming article in Physical Review Letters; Journalists: for a copy of the
article, contact AIP Public Informatin at physnews@aip.org)
ANTIMATTER TRAP Theodor Hansch and his colleagues at the Max Planck Institute
and the Unviersity of Munich in Germany have for the first time trapped
simultaneously electrons and positively charged ions in the same small region
of space. The researchers consider this to be "an important step towards the
synthesis of antihydrogen." Making antihydrogen -- consisting of a positron in
orbit around an antiproton -- would allow scientists to test the laws of
physics all over again, this time with antimatter. The hybrid Munich apparatus
consists of a Penning trap (a homogeneous static magnetic field and a static
electric quadrupole field) for confining the ions and a Paul trap (the static
electric quadrupole plus an oscillating electric quadrupole field) for
confining the electrons. As practice for making antihydrogen, the German
physiscists intend to stimulate the generation of ordinary hydrogen from
electrons and protons using a carbon dioxide laser. (J. Walz et al., upcoming
article in Physical Review Letters; contact physnews@aip.org)
A LASER IN THE SKY has been detected by the aricraft-mounted Kuiper
Observatory. Although astronomers have previously detected celestial masers --
coherent microwave emissions coming from gas clouds surrounding certain stars
-- the higher energy laser equivalent has been difficult to spot until now. The
laser emission (at a near IR wavelength of 169 microns) originates at a star
about 4000 light years away, probably from hydrogen in a circumstellar disk.
(Science, 8 September 1995) (Compiled by Mark Elowitz)