Technion researchers propose solution to a long-standing mystery of the Sun (Forwarded)
- From: Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 23 Feb 2007 13:49:38 GMT
Technion - Israel Institute of Technology
Technion City, Israel
Technion spokesman:
Amos Levav, 052-4524873
November 14, 2006
2081/06
Technion researchers propose solution to a long-standing mystery of the
sun
It Is Possible That the Source of the Chemical Composition of the Sun's
Corona Lies in Past and Present Flares
Researchers in the Technion's Faculty of Physics are proposing a solution
to a long-standing mystery of the sun -- how the sun's corona was created
and how it reached temperatures of millions of degrees, a thousand times
more than the sun itself. In an article to be published in the scientific
journal Astronomy & Astrophysics, the researchers say that it is possible
that the source of the sun's corona lies in flares, both past and present,
which enriched it.
The sun's corona is the hot, thin envelop of the star around which we
orbit. The temperature of the sun's corona reaches some millions of
degrees, approximately a thousand times more than the sun's yellow
surface. In addition, the corona's chemical composition differs from that
of the sun's surface. How was the sun's corona created? How did it reach
such high temperatures? What is the process responsible for the corona's
having a different chemical composition from that of the sun? These are
mysteries that have engaged scientists for decades.
Raanan Nordon of the Technion's Faculty of Physics and his doctoral
advisor, Dr. Ehud Behar, analyzed a series of observations, using NASA's
space telescope Chandra, relating to six neighboring stars to the sun with
extensive corona activities some thousands of times more energetic than
that of the sun.
"The tremendous temperatures of the star's coronas makes it impossible to
see them with a regular telescope in visible light," they explain. "But
Chandra is a telescope that is very sensitive to energy radiation, X-rays.
Sometimes flares occur in the stars' coronas, in which the flow of X-rays
from the star and the gas temperatures are a few fold higher."
Using Chandra's sensitive spectrometers, the Technion researchers
succeeded in measuring the chemical composition of the radiation sources.
That is, the concentrations of various chemical elements, such as oxygen,
neon, silicon and iron. They were surprised to find that apparently the
chemical composition of the stars' coronas changes during flares in an
unanticipated manner. Moreover, the stars' chemical composition was found
to be identical in its structure to the difference in the chemical
composition between our sun and its corona. For a long time, it was known
that the sun's corona is richer than the sun itself in atoms from which it
is relatively easy to extract an electron (to ionize). In addition, in
flares that were observed by the Technion researchers in the other stars,
it was found that the concentrations of these elements rose dramatically
during flares.
"The full significance of the findings is still not totally clear. But it
is possible that the chemical structures discovered in the stars hint at a
solution to the long-standing mystery of the chemical composition of the
sun's corona," the researchers say. "If, as was discovered in this
research, the flares push towards the corona easily ionized elements, is
possible that the source of the sun's corona is in past and present flares
that enriched it with these elements."
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