Number 243, October 5, 1995 by Phillip F. Schewe and Ben Stein
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 2 x 10**19 eV reveals a nonuniformity; the
rays seem to arrive preferentially from the "supergalactic plane,"
which, according to Todor Stanev of the Bartol Institute (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 would
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 nearby radio galaxies. (Todor Stanev et al., 23 October 1995,
Physical Review Letters; Journalists: for a copy of the article, contact
AIP Public Information at physnews@aip.org)
ANTIMATTER TRAP. Theodor Hansch and his colleagues at the Max Planck
Institute and the University 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 physicists intend to stimulate the generation
of ordinary hydrogen from electrons and protons using a carbon dioxide
laser. (J. Walz et al., 30 October 1995, Physical Review Letters; contact
physnews@aip.org)
A PHOTONIC WIRE LASER , devised by a Northwestern-UC San Diego-Cornell
collaboration, consists of a tiny ring-shaped optical fiber (where the
laser light is generated) coupled to a U- shaped fiber for carrying the
light away. With a cross section of only 0.19 x 0.4 microns and an active
laser volume of only 0.27 cubic microns (making this essentially the smallest
laser ever realized) the ring is a one-dimensional waveguide which because
of its small dimension makes more efficient use of the stimulated emission
than many other lasers. The researchers expect that their device will help
them to build other novel photonic nanostructures. (J.P. Zhang et al.,
Phys. Rev. Lett., 2 Oct.)
A LASER IN THE SKY has been detected by the aircraft-mounted Kuiper
Observatory. Although astonomers has 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.)
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