Explosive nuclear astrophysics

Date:
August 10, 2020
Source:
DOE/Argonne National Laboratory
Summary:
An international team has made a key discovery related to 'presolar
grains' found in some meteorites. This discovery has shed light
on stellar explosions and the origin of chemical elements. It has
also provided a new method for astronomical research.



FULL STORY ========================================================================== Analysis of meteorite content has been crucial in advancing our knowledge
of the origin and evolution of our solar system. Some meteorites also
contain grains of stardust. These grains predate the formation of our
solar system and are now providing important insights into how the
elements in the universe formed.


========================================================================== Working in collaboration with an international team, nuclear physicists
at the U.S. Department of Energy's (DOE's) Argonne National Laboratory
have made a key discovery related to the analysis of "presolar grains"
found in some meteorites. This discovery has shed light on the nature
of stellar explosions and the origin of chemical elements. It has also
provided a new method for astronomical research.

"Tiny presolar grains, about one micron in size, are the residue from
stellar explosions in the distant past, long before our solar system
existed," said Dariusz Seweryniak, experimental nuclear physicist in
Argonne's Physics division. The stellar debris from the explosions
eventually became wedged into meteorites that crashed into the Earth.

The major stellar explosions are of two types. One called a "nova"
involves a binary star system, where a main star is orbiting a white dwarf star, an extremely dense star that can be the size of Earth but have the
mass of our sun. Matter from the main star is continually being pulled
away by the white dwarf because of its intense gravitational field. This deposited material initiates a thermonuclear explosion every 1,000 to
100,000 years, and the white dwarf ejects the equivalent of the mass
of more than thirty Earths into interstellar space. In a "supernova,"
a single collapsing star explodes and ejects most of its mass.

Nova and supernova are the sources of the most frequent and violent
stellar eruptions in our Galaxy, and for that reason, they have been the subject of intense astronomical investigations for decades. Much has been learned from them, for example, about the origin of the heavier elements.

"A new way of studying these phenomena is analyzing the chemical and
isotopic composition of the presolar grains in meteorites," explained Seweryniak. "Of particular importance to our research is a specific
nuclear reaction that occurs in nova and supernova -- proton capture on an isotope of chlorine - - which we can only indirectly study in the lab."
In conducting their research, the team pioneered a new approach for astrophysics research. It entails use of the Gamma-Ray Energy Tracking
In-beam Array (GRETINA) coupled to the Fragment Mass Analyzer at
the Argonne Tandem Linac Accelerator System (ATLAS), a DOE Office of
Science User Facility for nuclear physics. GRETINA is a state-of-the-art detection system able to trace the path of gamma rays emitted from
nuclear reactions. It is one of only two such systems in the world.

Using GRETINA, the team completed the first detailed gamma-ray
spectroscopy study of an astronomically important nucleus of an isotope, argon-34. From the data, they calculated the nuclear reaction rate
involving proton capture on a chlorine isotope (chlorine-33).

"In turn, we were able to calculate the ratios of various sulfur isotopes produced in stellar explosions, which will allow astrophysicists to
determine whether a particular presolar grain is of nova or supernova
origin," said Seweryniak. The team also applied their acquired data
to gain deeper understanding of the synthesis of elements in stellar explosions.

The team is planning to continue their research with GRETINA as part of a worldwide effort to reach a comprehensive understanding of nucleosynthesis
of the elements in stellar explosions.


========================================================================== Story Source: Materials provided by
DOE/Argonne_National_Laboratory. Original written by Joseph
E. Harmon. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. A. R. L. Kennington, G. Lotay, D. T. Doherty,
D.

Seweryniak, C. Andreoiu, K. Auranen, M. P. Carpenter,
W. N.

Catford, C. M. Deibel, K. Hadyńska-Klęk,
S. Hallam, D. E. M. Hoff, T. Huang,
R. V. F. Janssens, S. Jazrawi, J. Jose',
F. G. Kondev, T. Lauritsen, J. Li, A. M. Rogers,
J. Saiz, G. Savard, S. Stolze, G. L. Wilson, S. Zhu. Search
for Nova Presolar Grains: g-Ray Spectroscopy of Ar34 and its
Relevance for the Astrophysical Cl33(p,g) Reaction. Physical Review
Letters, 2020; 124 (25) DOI: 10.1103/PhysRevLett.124.252702 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200810141000.htm

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