For Additional Information:
Dr. John Gregory, (205) 890-6028
Phillip Gentry, (205) 890-6414
[email protected]
Cosmic rays from the supernova next door?
Expanding outward for millenia, shock waves from exploding supernova
stars ram into atoms in interstellar space, sending their nuclei zipping
through the galaxy at almost the speed of light.
This theory satisfactorily explains the creation of most of the cosmic
rays which hit Earth's atmosphere. It cannot, however, explain the
creation of cosmic rays which carry the highest levels of energy.
"Standard cosmic ray theory says a single cosmic ray can't be accelerated
much beyond 10 to the 14th or 10 to the 15 electron volts, because
there's just so much power in a supernova," said Dr. John Gregory, a
professor of chemistry at The University of Alabama in Huntsville. Where
then is the origin of cosmic rays with higher energies?
Using detectors which "orbit" the Antarctic beneath giant balloons,
Gregory and Dr. Yoshiuki Takahashi, a research professor of physics, may
have collected enough rare high energy cosmic rays to answer that question.
While the number of cosmic rays decreases as energy increases, when the
UAH team looked at the highest energy cosmic rays they found more than
they expected. And the "mix" changed. While lower energy cosmic rays have
roughly the same mix of elements as the solar system, higher energy
cosmic rays have more "heavy" elements, such as iron and carbon, and less
hydrogen and helium.
"It's as if the source of lower energy particles has run out of steam and
we're looking at a new source," Gregory said. "Our data no longer fits
the standard model."
A new theory suggests that high energy cosmic rays come from binary star
systems containing a recent supernova and a giant star which has blown
most of the lighter elements off its surface. Heavier elements from the
giant star's core are expelled and further accelerated by strong shock
waves from its supernova neighbor. This may be the first hard evidence
for identifying specific stellar objects as cosmic ray sources.
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