|
BALLOON
ABOVE CANADA SEARCHES FOR ANTIMATTER AND OTHER COSMIC PARTICLES
Caption:
Wallops Balloon With BESS Payload Prepares for Launch
BALLOON
ABOVE CANADA SEARCHES FOR ANTIMATTER AND OTHER COSMIC PARTICLES
High
above the Canadian plains, Japanese and U.S. scientists have
harvested another crop of antimatter particles, in the latest
flight of a balloon-borne experiment named BESS which has
flown nearly every summer since 1993 searching for evidence
of an antimatter domain within our Universe.
BESS
(Balloon-borne Experiment with a Superconducting Spectrometer)
lifted off from Lynn Lake in Manitoba, Canada, August 7 at
8:58 p.m. local time on a 22 hour flight. The 5,300-pound
experiment flew beneath a 40-million-cubic-foot balloon, NASA's
largest, at an average altitude of approximately 23 miles.
BESS was retrieved last night near Fort McMurray, Alberta,
and the team will now begin sorting through the new data.
Dr.
Akira Yamamoto of the High Energy Accelerator Research Organization
in Japan (known as KEK) and Dr. John Mitchell of NASA's Goddard
Space Flight Center in Greenbelt, Maryland, co-lead this international
experiment, which is jointly sponsored by the Ministry of
Education, Culture, Sports, Science and Technology (MEXT)
of Japan and NASA.
Antimatter
particles are forms of matter with electrical charges exactly
the opposite of their ordinary "sister" particles.
Whereas a proton has a positive charge and an electron has
a negative charge, an antiproton has a negative charge and
an antielectron (or positron) has a positive charge. The simplest
version of the Big Bang theory predicts there are equal amounts
of matter and antimatter in the Universe, yet scientists have
largely detected only ordinary matter.
BESS
contains an instrument that detects a variety of cosmic rays,
which are atomic particles moving through space at nearly
the speed of light. Some of these particles are antiprotons
created by collisions of ordinary matter deep in space. The
strong magnetic field of the BESS superconducting magnet in
conjunction with its high-resolution particle detectors enables
a very sensitive search for antimatter in the Universe.
If
BESS were to find a sophisticated form of antimatter, such
as an anti-helium nucleus, it would provide evidence that
antimatter galaxies exist. Anti-helium is virtually impossible
to create by any known process, such as an ordinary particle
collision, and would have to come from a source composed of
antimatter.
"It
is still a fundamental question why we do not observe antimatter
balancing with matter in the Universe," said Yamamoto.
"We have actually found no anti-helium in our data taken
during the seven flights from 1993 to 2000, while we have
detected seven million helium nuclei. That fact provides the
most direct evidence that our Galaxy and those nearby are
made solely of matter, not antimatter. Why does nature appear
to have not taken the simple path of matter and antimatter
balance?"
Theories
have been proposed to explain the apparent dearth of antimatter
in the Universe. Russian physicist Andrei Sakharov proposed
three conditions in 1967 that, if met, would allow a predominance
of matter over antimatter in the early Universe. In the laboratory
setting, physicists have demonstrated that some of these conditions
can be met, but it is not proven that all are met.
As
in years past, BESS' August 2002 catch will likely yield antiproton
cosmic rays among the millions of particles detected. Even
though most of the antiprotons are created as "secondaries"
in well-understood cosmic-ray collisions in deep space, there
might be a chance to detect antiprotons of cosmic-origin such
as primordial black holes that might be created in the very
early Universe.
"It
would be of extraordinary interest if BESS were to detect
antiprotons in excess of those expected as secondary particles,"
said Mitchell. "There are hints in the current data,
but, as always, more data is needed."
Balloons
offer an inexpensive platform to search for antimatter. After
each yearly flight, the BESS team improves the instrument
for the next flight, resulting in a steadily increasing number
of particles collected. The next BESS flight is anticipated
for Antarctica in December 2003 and January 2004, where scientists
hope to fly the experiment for two weeks continuously, collecting
a large amount of data.
The
BESS collaboration includes researchers at NASA Goddard and
the University of Maryland in the United States; and at the
High Energy Accelerator Research Organization, Kobe University,
the University of Tokyo, and the Institute of Space and Astronautical
Science, all in Japan.
The
balloon campaign in Canada is conduced by the National Scientific
Balloon Facility, Palestine, Texas, through the NASA Scientific
Balloon Project Office at Goddard's Wallops Flight Facility,
Wallops Island, Virginia. In addition to the BESS flight,
two flights will be conducted from Lynn Lake in August for
the University of Delaware.
Back
to Top
|
