[meteorite-list] NRL and Carnegie Institution Scientists Examine the Life Cycle Of Stars Encoded In Tiny Grains Of Dust

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Sep 13 16:25:55 2004
Message-ID: <200409132025.NAA23499_at_zagami.jpl.nasa.gov>

Public Affairs Office
Naval Research Laboratory
Washington, D.C.

9/2/2004

Press Release 45-04r

NRL and Carnegie Institution Scientists Examine the Life Cycle Of Stars Encoded
In Tiny Grains Of Dust

Scientists at the Naval Research Laboratory and the Carnegie Institution of
Washington are studying microscopic aluminum oxide stardust grains that predate
the Sun. The analysis of the grains gives unique insight into the processes by
which old stars shed dust that then becomes the raw material for the birth of
new stars.

Dr. Rhonda Stroud, a research physicist in NRL's Materials Science and
Technology Division, explains that the research team is "reverse engineering
stars," by analyzing the presolar dust grains. Dr. Larry Nittler and Dr. Conel
Alexander, from the Carnegie Institution of Washington, perform measurements of
the oxygen and magnesium isotopes in the dust grains. These measurements reveal
what kind of star the dust came from. Armed with these results, Dr. Stroud
extracts 100-nanometer thin sections from the dust grains using techniques
usually applied to site-specific defect analysis in microchips. Then she
analyzes the structure of the dust using a transmission electron microscope.
Once the structure of the dust is known, it is possible to infer the
environmental conditions of stellar outflows in which the dust formed.

The research team discovered that O-rich asymptotic giant branch (AGB) stars
produce aluminum oxide in crystalline and amorphous forms. These findings are
important for Department of Defense researchers interested in what kinds of
materials form in extreme environments, and can survive long-term exposure to
the harsh radiation environments of space.

The physical data from the grains is also useful to astrophysicists who have
been debating for 30 years the sequence of dust formation, and how materials get
recycled from stars and interstellar-space. Now the astrophysicists can directly
compare the data from the grains, to the predictions of the dust condensation
models. The data provide strong support to models of AGB stars that predict that
aluminum oxide phases are the first to condense. The observational astronomy
community will also benefit from having definitive evidence for the existence of
two forms of aluminum oxide. The interpretation of IR spectra from the dust
clouds around O-rich AGB stars has provoked intense debate over what type of
aluminum oxide, if any, exists in these clouds. The analysis of the NRL-Carnegie
team bridges the information gap faced by astrophysicists and astronomers by
providing complete chemical, isotopic, and structural profiles of individual
dust grains.

This research is being funded by the Office of Naval Research and the National
Aeronautics and Space Administration. The results of this research are published
in the 9/3/04 issue of Science.

IMAGE CAPTION:
[http://www.nrl.navy.mil/pao/PressReleases/2004/45-presolargrain.jpg (37KB)]
This scanning electron microscope image shows one of the aluminum oxide stardust
grains studied by the NRL/Carnegie Institution research team.
Received on Mon 13 Sep 2004 04:25:26 PM PDT