Scientific Balloon Circles South Pole on Search for Antimatter
BESS-Polar shortly before its
on Dec 13, 2004 from Antarctica.
(PHOTO CREDIT: NASA)
A group of Japanese and American scientists bundled in thick orange
jackets, hats, boots and gloves have ventured down to
Antarctica on a search for antimatter. With their high-altitude
balloon-borne instrument, they are in an exotic land to learn about
The instrument, called BESS-Polar, launched successfully on
December 13 from McMurdo Station, Antarctica beneath a
40-million-cubic-foot scientific balloon as big as a football
field. It remained aloft until December 21 at an average altitude
of 24 miles (39 kilometers), a near-space environment above 99%
of the atmosphere. The instrument traveled nearly once around
the South Pole.
The team seeks to understand the origin of cosmic antimatter and to
find evidence for the existence of Hawking radiation from "evaporating"
black holes, a theory proposed by Prof. Stephen Hawking of Cambridge
University in England. The long flight for BESS-Polar was intended to
maximize the possibility of finding this antimatter predicted by Hawking.
"Our earlier, shorter flights from northern Canada have provided
hints of the signature of Hawking radiation," said Principal
Investigator Prof. Akira Yamamoto of Japan's High Energy Accelerator
Research Organization (KEK). "With a longer flight and a greater
'harvest' of antiprotons, we might be able to show that Prof.
Hawking is right."
BESS-Polar is collaboration among scientists at KEK, the
University of Tokyo, Kobe University, and the Institute of
Space and Astronautical Science of the Japan Aerospace Exploration
Agency, along with NASA and the University of Maryland, College Park.
BESS stands for Balloon-borne Experiment with Superconducting
The BESS-Polar team in Antarctica
(PHOTO CREDIT: NASA)
Antimatter is made up of particles with equal but opposite
characteristics of the particles of matter we interact with
everyday. For example, protons have a positive charge, but
antiprotons have a negative charge. Antiprotons created in
space bombard the Earth in the form of cosmic rays, which are
elementary particles traveling at near light speed. When
matter and antimatter collide, they annihilate, creating
pure energy and no "ash".
The most basic form of the Big Bang theory predicts that
equal amounts of matter and antimatter were created. If so,
all matter would have annihilated and the Universe would be
empty. Somehow, matter dominated antimatter in the initial
moments following the Big Bang. One of the BESS-Polar project's
goals is to see if there is any evidence of antimatter domains
left over from the Big Bang.
Another of BESS-Polar's goals is to search for Hawking radiation.
Just outside the event horizon of a black hole, virtual particles
may be created for a very short amount of time from quantum
fluctuations in the vacuum of space. These particles are created in
matter-antimatter pairs. If this occurs close to the event horizon,
one of the members of the pair can fall into the black hole, while the
other remains outside. This produces a "radiation" from the black hole
that Hawking predicted.
The study of lower-energy antiproton particles is particularly
exciting, Yamamoto said, because they might have been created by
"evaporating" black holes which are emitting Hawking radiation.
This type of radiation has not
yet been seen in nature. This would be from primordial, microscopic
black holes created just after the Big Bang. Finding antiproton
particles in an abundance and energy range predicted by theory
would serve as compelling evidence.
"The northern and southern polar regions are the best places
to collect low-energy antiprotons," said U.S. Principal Investigator
Dr. John Mitchell of NASA Goddard Space Flight Center, at McMurdo
Station for the flight. "The Earth's magnetic field protects us
from antiprotons and other cosmic-ray particles from space. The
magnetic field funnels charged particles toward the Earth's poles,
so the concentration of lower-energy cosmic rays entering into
the Earth's atmosphere there is greater."
This is the first flight for BESS-Polar. Scientists have flown
an earlier version called BESS for daylong flights in northern
Canada once a year nearly every year from 1993 to 2002. That
instrument collected millions of cosmic rays and a few thousand
low-energy antiprotons. But more are needed for better analysis.
"We journeyed to the bottom of the world so that we could get
a nice, long flight," said Project Manager Prof. Tetsuya Yoshida
of KEK. "Longer flights mean better statistics." In addition, a
longer flight increases the ability to get to lower energy
antiprotons (which helps detect the Hawking radiation).
Constant daylight in Antarctica means no day-to-night temperature
fluctuations on the balloon craft, which helps the balloon stay at
a constant altitude for longer. The BESS-Polar team hopes to collect
enough antiprotons to characterize their absolute intensity (number
per square meter per second per solid angle) among other the cosmic
rays in terms of energy.
The Wallops Flight Facility, Wallops Island, Va., manages the
Scientific Balloon Program for NASA. The National Scientific Balloon
Facility located in Palestine, Texas, manages NASA's balloon launch
operations. The National Science Foundation Office of Polar Programs
operates McMurdo Station.
For more information and images from Antarctica, refer to http://bess-gsfc.gsfc.nasa.gov.
Visit the BESS homepage. (http://www.universe.nasa.gov/astroparticles/programs/bess/)