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Topic Name: Fe-60 in the galaxy
Category: STAR (Space, Telecommunications & Radioscience)
Research persons: Wang W., Harris M., Diehl R., Halloin H., Cordier B., Strong A.W., Kretschmer K., Knödlseder J., Jean P., Lichti G.G., Roques J. - P., Schanne S., of Kienlin A., Weidenspointner G., Wunderer C
Location: Pouring brook route,85748 Garching,Max-Planck company, Munich,Fon: +49 (89) 30000 - 0, Germany
Details
With the European gamma satellite
scientists radioactive iron discovered INTEGRAL within the Milky Way. Although
the iron atoms are distributed in the interstellar gas - thus outside of the
stars -, permit it as it were a view in the inside of those massive suns, which
coin/shape our galaxy and its spiral arms. The proof of the isotope Fe-60
succeeded to a team around Roland Diehl of the institute for Max-Planck for
extraterrestrial physics in Garching with Munich.
For a long time the
researchers search for radioactive iron in the interstellar area. Before nearly
30 years there already radioactive aluminum was found, and 1999 discovered a
group of the technical University of Munich in a sample from the southPacific
ocean crust traces of Fe-60. This iron isotope should occur also in the
interstellar gas. Actually there were promising references, which were however
interpretation dependent in the past years and controversially were evaluated.
For their search the astrophysicists used now a gamma
spectrometer on INTEGRAL. Since October 2002 the satellite of the European space
travel agency ESA the sky in the light of gamma-rays high-energy misses. Now the
scientists sought out the finger marks of the material desired around Roland
Diehl by the institute for Max-Planck for extraterrestrial physics with the
observatory in the earth orbit: Signals with the two energies characteristic of
the radioactive decay of Eisen-60 1173 and 1333 Kilo electronvolts (keV). The
observed gamma lines develop, if Eisen-60 with a radioactive half-life of 1.5
million years first to short-lived Cobalt-60 and then (radioactive half-life 5.3
years) to stable Nickel-60 disintegrates.
Roland Diehl believes that thereby an important step succeeded
to understand the element emergence in massive stars: “We discussed lately
some reports to the alleged find of Eisen-60. But the spectrometer on board
INTEGRAL is meanwhile the only instrument, which can accomplish this measurement
exactly enough. Now are we surely that radioactive Eisen-60 in our galaxy exists
spaciously, this very day produce ourselves and disintegrate.”
The definite proof opens a window the most inside the most
massive stars of the Milky Way. These gas balls unite more than the tenfold
solar mass in itself and live briefly however intensively: From the birth to its
end in an enormous supernew fact explosion offense straight once 100 million
years. In the comparison to it ours is nearly five billion years old sun a
stellar Methusalem. The massive stars are the breeding places of most chemical
elements in the universe.
While the Big Bang essentially produced 13.7 billion years ago
hydrogen and helium, the interstellar gas enriched itself only in the course of
the time with the heavier elements, which again resulted in the respective star
generation from nuclear reactions. If massive stars contain then already small
quantities iron of later generations, neutron capture reactions can run off
there, which make the heavier Fe-60 from the sturdy iron isotopes.
So far the astrophysicists could rely with core-physical
studies of the emergence of new elements in the today's universe on only one
element: for the first time the Aluminium-26-Isotop sought out in the year 1978
of an American satellite. It disintegrates with a radioactive half-life of
740,000 years and meanwhile by several telescopes in different way was measured.
“Studies to radioactive Aluminium-26 developed to their own astronomical
range”, say Roland Diehl.
Eisen-60-Radioaktivität gives new possibilities, since it is
produced in the same star types as Aluminium-26, to the astrophysicists however
in other regions and to other development phases - later and further inside.
Massive stars go through successively phases of the nuclear fusion from first
easy to increasingly heavier elements (the latters call astronomers
“metals”) and develop so their characteristic bulb-flat-similar internal
structure.
Eisen-60 develops in the zones mixed well by convection, in which helium and
carbon fusion reactions run off. That happens however so late in the development
cycle of the star that the radioactive ash of these zones is only hurled by the
supernew facts at the end of the star life into free space. With radioactive
Aluminium-26 one assumes that already the products of early, also Aluminium-26
producing fusion phases contain the intensive star hoist of the so-called wolf
Rayet phase.
“Eisen-60 is our Eingangstor to the studies, which examine, say neutron
capture reactions in current star generations” Max-Planck researcher Diehl.
“Some nuclear physics laboratories again presented measurements, in order to
be examined and checked the radioactive decay of different iron isotopes, like
easily or heavily neutrons by these isotopes being caught can.”
With INTEGRAL in the past years new and highly detailed measurements succeeded
to Aluminium-26. Therefore the astrophysicists can the relationship of the gamma
radiation from Eisen-60 to Aluminium-26 now exactly intend - and thus the model
conceptions for the element emergence in these stars test. Studies predicted
values between 10 and 100 in the past decade for the isotope relationship,
whereby the newest forecasts stand fortunately with the integral measurements in
agreement. That could be however rather lucky adding. The results to Eisen-60
stimulated theoreticians and core physicists to take this test now again more
exactly under the magnifying glass.
Although INTEGRAL sees the gamma radiation of the interstellar Eisen-60 clear,
the intensity is still too small, in order to provide an image of the sky (an
intensity map). It would be interesting to compare the bright and dark places of
the Milky Way level in the gamma light of Eisen-60 with from Aluminium-26 to.
The next integral operational years want to use the Max-Planck researcher, in
order to receive first conceptions of it. “The cartography of the distribution
of Eisen-60 in our galaxy is a project for a future generation of gamma
telescopes”, says Roland Diehl.
About The Researcher-
Priv.Doz. Dr. Roland
Diehl
Institute
for Max-Planck for extraterrestrial physics, Garching
Tel.: +49 89 30000-3850
Fax: +49 89 30000-3569
E-Mail: rod@mpe.mpg.de
Funded-
Institute
for Max-Planck for extraterrestrial physics
Original
publication:
Wang W., Harris M., Diehl R., Halloin H., Cordier B., Strong
A.W., Kretschmer K., Knödlseder J., Jean P., Lichti G.G., Roques J. - P.,
Schanne S., of Kienlin A., Weidenspointner G., Wunderer C.
MIRROR-IMAGE observations OF the vague 60Fe emission into the
Galaxy
Astronomy & Astrophysics, DOI: 10.1051/0004 6361:
20066982; appeared in the ARXIV Preprint service as arXiv: 0704.3895
In The Images-
Priv.Doz. Dr. Roland
Diehl & The
finger mark of the radioactive decay of Fe-60 in the interstellar gas of our
galaxy: In this diagram both gamma lines are overlaid with their target being
(1173 and 1332 keV), in order to make the weak signal measured with INTEGRAL
visible.
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