archive: SETI FW: [ASTRO] PHYSICS NEWS UPDATE

SETI FW: [ASTRO] PHYSICS NEWS UPDATE

Larry Klaes ( lklaes@zoomtel.com )
Wed, 23 Sep 1998 13:29:58 -0400

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From: William J. Larson
Sent: Tuesday, September 22, 1998 11:53 PM
To: ASTRO
Subject: [ASTRO] PHYSICS NEWS UPDATE

PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 392 September 22, 1998 by Phillip F. Schewe and Ben
Stein

DO COSMIC RAYS COME FROM QUASARS? Cosmic ray
particles, which crash into Earth's atmosphere setting up huge
showers of particles detected on the ground, have mysterious
origins. Looking at the five most energetic events ever recorded
(energies above 10^20 eV), Glennys Farrar of NYU
(farrar@physics.nyu.edu) and Peter Bierman of the Max Planck
Institute for Radio Astronomy in Bonn have found that all the
events are consistent with the cosmic rays having originated in
radio-loud quasars with redshifts in the range 0.3-2.2, and
propagating undeflected and unattenuated in energy through the
intervening thousands of Mpc (Physical Review Letters, tentatively
19 October 1998). If the particles (conventionally assumed to be
protons) are indeed coming from a great distance then how do they
evade the Greisen-Zatsepin-Kuzmin (GZK) cutoff, according to
which cosmic rays with energies above about 10^19.5 eV would be
sapped of their energy through interactions with cosmic microwave
background photons if they traveled much more than 20 Mpc
(roughly 60 million light years)? Such interactions would typically
produce pions and electron-positron pairs. Some speculate that the
high-energy particles are not protons at all but some exotic new
particle. One explanation is that energetic neutrinos make the long
cosmic journey and then annihilate relatively near the Earth with
massive dark-matter neutrinos to create the cosmic ray primary
particle. Farrar herself is partial to the notion that the primary is
the neutral S particle, an amalgam of three quarks and a gluino (one
of the shadow particles associated with supersymmetry theory; see
Updates 86 and 265). With a mass two or three times that of the
proton, the S would not as readily produce pions in interactions
with microwave photons, thus ensuring for itself a more robust
passage through the cosmos. Thus the highest energy cosmic rays
could be produced at cosmological distances but still survive the trip
to Earth. (Physics Today, October 1998.) Future measurements
determining whether the primary is a photon or hadron will help
decide the question of whether the correlation between cosmic rays
and quasars holds up.

THE 25 GREATEST ASTRONOMICAL FINDINGS of all time,
according to the editors of Astronomy magazine (October 1998) are
as follows: the discovery of quasars (1963); the cosmic microwave
background (1965-66); pulsars (1967); Galileo's observations of the
phases of Venus, Jupiter's moons, and craters on the moon (c
1609); extrasolar planets (1992); supermassive black holes (early
1990s); Newton's Principia, formulating the mathematics of our
heliocentric system (1687); the discovery of Uranus (1781); the first
known asteroid (1801); discovery of Pluto (1930); Neptune (1846);
spectroscopic proof that nebulae are gaseous in nature (1864);
recognition of galaxies beyond our own (1923); the advent of radio
astronomy (1931-32); studies of globular clusters help to map the
Milky Way (1918); cometary explosion over Siberia (1908); an
accurate measurement of the speed of light (1675); Southern
Hemisphere celestial objects cataloged (1834-38); Cepheid-variable
period-luminosity relationship worked out (1912); Copernicus' De
Revolutionibus sets forth the heliocentric system (1543); Laplace's
theory on how the solar system formed (1796); a transit of Venus
suggests Venus has an atmosphere (1761); the Hertzsprung-Russell
diagram for understanding how stars age (1913); scheme for
classifying star types (1890); the use of parallax for finding a star's
distance from Earth (1838).