venerdì 24 aprile 2009


Sampling Interstellar Matter/La materia interstellare

Interstellar Probe will make the first comprehensive, direct measurements of the composition of interstellar dust, and of the elemental and isotopic composition of the ionized and neutral components of the interstellar gas.
The predominantly nearby interstellar medium contains elements that are ionized (e.g. C, S and Si), those that are to a large extent neutral (H, He, N, O, Ne and Ar), and others that are predominantly condensed into dust grains (Al, Ca, Mg and Fe). Of these, the lightest elements (H, He, and Li) were created in the Big Bang, while heavier elements are created by nucleosynthesis in stars and then ejected into interstellar space by stellar winds and supernova explosions.
The local cloud includes younger material than that of the presolar nebula.
It is therefore expected to be richer in heavier elements and neutron-rich isotopes as a result of continuing nucleosynthesis.
By sampling matter in all three states - solid (dust), gas (neutral) and plasma (ionized) - Interstellar Probe will obtain a complete sample of the elemental and isotopic abundances that can serve as a standard reference for the composition of interstellar material.
Comparisons of this benchmark with the solar system abundances and with abundances from more distant galactic regions will provide important constraints on theories of galactic chemical evolution.
Measurements of isotopic abundances, including 2H, 3He, 13C, 18O, 22Ne, 26Mg, and 30Si will constrain cosmological and nucleosynthesis models to provide a more accurate model of the evolution of the solar system, the galaxy, and the universe.

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