WIMPZILLAS May Solve Cosmic Puzzles
Posted September 23, 2002
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FOR IMMEDIATE RELEASE - September 23, 2002 2002-09-19-AR
WIMPZILLAS May Solve Cosmic Puzzles
Ultra-high energy cosmic rays travelling at nearly the speed of light shoot
through the galaxy from all directions, striking Earth's atmosphere roughly
every six seconds. Most cosmic rays originate from stars, but the energy
source for these ultra-high energy rays has been a mystery -- until now.
University of Saskatchewan astrophysicist Rainer Dick and international
colleagues have proposed a new theory that may explain this momentous puzzle
in contemporary particle astrophysics.
"Scientists have been trying to determine the origin of ultra-high energy
cosmic rays for almost 40 years," said Dick. "These cosmic rays strike Earth
with such high energies (comparable to the energy of a tennis ball moving at
100 kilometres per hour) that we know they can't have travelled from another
galaxy. So they must have originated within our own."
Dick hypothesizes that super-heavy particles of dark matter called
WIMPZILLAS are responsible for the existence of ultra-high energy (UHE)
cosmic rays.
Dark matter is made of invisible particles generated at extremely high
temperatures mere seconds after the universe was created. These particles
usually don't give off or absorb light except when two of them collide and
annihilate in a burst of radiation.
WIMPZILLAS are the Godzilla-sized version of dark matter particles called
Weakly Interacting Massive Particles (WIMPS). WIMPZILLAS weigh only a
trillionth of a gram, but that's more than 100 billion times the mass of an
atom -- heavier than any other known elementary particle.
Dick thinks that WIMPZILLAS clump together in the dark matter halo
surrounding our galaxy. When two of them collide and are annihilated, they
release extremely high amounts of energy -- UHE cosmic rays.
His theory challenges a 1997 theory put forward by a Russian team and a
US-Italian-German collaboration that a single dark matter particle
deteriorates, resulting in UHE cosmic rays.
Cosmic rays were first discovered back in 1912, but UHE cosmic rays weren't
observed until the 1960s with the advent of ground-based cosmic ray
detectors.
New Scientist has published an article on WIMPZILLAS by Dick's team in its
June issue. A paper explaining their idea will appear in the September issue
of Astroparticle Physics.
The existence of WIMPZILLAS may also solve a second puzzle -- the missing
mass of the Universe.
Most of the matter in the universe is clustered into galaxies, but only a
tiny fraction of it, such as stars or planets, is visible. Scientists
measure the mass of a galaxy by determining how fast it rotates, or by
observing how light rays are bent in its gravitational field. What they
find is that galaxies weigh more than the sum of their stars.
"We know that the mass of the galaxy is made up of much more than stars,"
said Dick.
"Massive dark matter particles, WIMPZILLAS, account for the missing mass."
The theory will be tested at the Pierre Auger Observatory now under
construction in Argentina. Over the first three or four years of operation,
hundreds of UHE cosmic rays will be tracked and studied using 1,600 cosmic
ray detectors over 3,000 square kilometers.
Co-developers of the WIMPZILLA theory are Edward Kolb of the Enrico Fermi
Institute in Chicago and Pasquale Blasi of the Arcetri Astrophysical
Observatory in Florence, Italy.
Funding was provided by NSERC (Natural Sciences and Engineering Research
Council) and NASA/Fermilab Astrophysics Center.
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For more information, contact:
Professor Rainer Dick
Physics Department
University of Saskatchewan
(306) 966-6443
Kathryn Warden
Research Communications
University of Saskatchewan
(306) 966-2506
