New method pioneered by international team could shed light on the origin of interstellar paricles

A new method being pioneered by nuclear physicists at the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory and an international team promises to help scientists studying the origin of particles found on meteorites to determine whether they came from novas or supernovas.

There are mainly two types of explosions that produce the particles, called presolar grains, according to a press release from the Argonne National Laboratory. Those are supernovas – the massive ejection of the majority of the material of a single star when it collapses – and novas.

Novas occur when a white dwarf – a star the size of earth but with the mass of our sun – in a binary system strips material from the star it is orbiting, according to the release. Every 1,000 to 100,000 years, the stripped material creates a thermonuclear explosion, ejecting mass approximately equal to 30 earths from the white dwarf.

The resulting material is deposited on meteorites as presolar grains, and scientists are able to retrieve meteorites that have crashed to earth in order to study the material.

“Tiny presolar grains, about one micron in size, are the residue from stellar explosions in the distant past, long before our solar system existed,” Dariusz Seweryniak, experimental nuclear physicist in Argonne’s Physics division, said in the press release. 

The team uses 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, according to the release. GRETINA is one of only two systems in the world able to trace the path of gamma rays emitted from a nuclear explosion.

With those resources, the team was able to conduct a detailed gamma ray spectroscopy study of argon-34 and use the data to calculate the nuclear reaction rate involving proton capture on a chlorine isotope (chlorine-33), according to the release.

“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,” Seweryniak said in the press release.