"This is a fundamental new discovery about how our planet works," expert says.
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An illustration shows high-energy electrons
and positrons from Earth traveling into space.
Illustration courtesy J. Dwyer/FIT, NASA
Published January 11, 2011
Thunderstorms can shoot beams of antimatter into space
and the beams are so intense they can be spotted by
spacecraft thousands of miles away,
scientists have announced.
Most so-called normal matter is made of subatomic particles such as electrons
and protons.Antimatter, on the other hand, is made of particles that have
the same masses and spins
as their counterparts but with opposite charges and magnetic properties.
Recently,
radiation detectors on NASA's Fermi Gamma-ray Space Telescopelighted
up for about 30 milliseconds with the distinctive signature of positrons,
the antimatter counterparts of electrons.
Scientists were able to trace the concentrated burst of radiation to a l
away from the Earth-orbiting telescope,
which was passing above Egypt at the time. (See an Africa map.)
"This is a fundamental new discovery about how our planet works,"
said Steven Cummer, a lightning researcher from Duke University
who was not part of the study team.
"The idea that any planet has thunderstorms that can create
antimatter and launch it into space is something out of science fiction.
The fact that our own planet is doing it is truly amazing."
Intense Antimatter Beam a Shocker
Scientists already knew that thunderstorms can emit gamma rays
can create positrons through a process called pair formation.
When a gamma ray with the right amount
of energy interacts with an air atom,
energy from the gamma ray is converted into matter,
one electron and one positron,
lightning expert Joseph Dwyer said yesterday during a meeting
of theAmerican Astronomical Society in Seattle, Washington.
Scientists wouldn't have been surprised to see a few positrons
accompanying any intense gamma ray burst, added Dwyer,
of the Florida Institute of Technology in Melbourne.
But the lightning flash detected by Fermi appeared to
have produced about 100 trillion positrons: "That's a lot," he said.
What seems to have happened is that positrons created by the
lightning were herded into a tight beam by Earth's magnetic field,
said study leader Michael Briggs of the University of Alabama, Huntsville.
The beam funneled positrons from the Namibian storm to the Fermi spacecraft.
A few milliseconds after hitting the spacecraft,
the beam struck a more northerly section of Earth's magnetic field,
Briggs added. This caused some of the positrons to bounce back
the way they had come, hitting the spacecraft with a second beam,
like an echo.
Antimatter a Clue to Lightning
Earth is constantly being bombarded by radiation from the sun,
as well as cosmic rays from distant but violent events,
such as powerful supernovae.
Considering the amount of positrons in the beam Fermi detected,
the thunderstorm was briefly creating more radiation
in the form of positrons and gamma rays—than what hits
Earth's atmosphere from all other cosmic sources combined, Dwyer noted.
The researcher has previously said, however,
Duke's Cummer added that nobody knows why some
thunderstorms produce gamma rays while most do not.
"We really don't understand a lot of the details about how lighting works,
" he said. But discovering the creation of positrons "gives us a very,
very important clue as to what's happening."
A paper about the discovery of antimatter in
thunderstorms has been accepted for publication in the journal
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