Rare cosmic reaction recreated
- Researchers recreated a rare cosmic nuclear reaction in the lab, according to social science posts. (x.com) - The experiment was highlighted for matching conditions that typically occur in exotic astrophysical environments. (x.com) - Lab recreation of cosmic reactions helps test models of stellar processes otherwise only inferred from observation. (x.com)
Stars make many heavy elements by adding neutrons, but a small set of proton-rich atoms follows a different route. In a new lab test, researchers directly measured one of those rare reactions for selenium-74. (frib.msu.edu) The team used a radioactive beam of arsenic-73 and sent it into a hydrogen-gas target at Michigan State University’s Facility for Rare Isotope Beams, or FRIB. When arsenic-73 captured a proton, it formed selenium-74, letting the group measure a reaction that had not been directly tested this way before. (frib.msu.edu) The results were published in *Physical Review Letters* on November 20, 2025, in a paper titled “Constraining the Synthesis of the Lightest p Nucleus 74Se.” The experiment measured the reaction at effective center-of-mass energies of 2.9 and 2.3 mega-electron volts per nucleon. (link.aps.org) Nuclear astrophysics studies how reactions inside stars and stellar explosions build the periodic table. Most nuclei heavier than iron are explained by slow or rapid neutron capture, but proton-rich “p-nuclei” such as selenium-74 are not. (frib.msu.edu) Selenium-74 is the lightest known p-nucleus, and its origin has been debated for decades. FRIB said the leading explanation is the gamma process in some supernova explosions, where intense gamma rays knock neutrons and other particles out of existing nuclei. (phys.org) That matters because models of the gamma process still rely heavily on theory for short-lived isotopes that are hard to make on Earth. Artemis Tsantiri, who led the work as a FRIB graduate student and is now at the University of Regina, said measurements of key reactions on short-lived isotopes are “almost non-existent.” (phys.org) The new measurement does not close the case on where selenium-74 comes from. The *Physical Review Letters* abstract says the data constrain a main destruction path for selenium-74 in explosive stellar environments and help pin down the reaction cross section in the upper “Gamow window,” the energy range where stellar reactions are most likely to occur. (link.aps.org) The project involved more than 45 researchers from 20 institutions in the United States, Canada, and Europe. For nuclear astrophysicists, the point of recreating a cosmic reaction in the lab is simple: replace one more theoretical estimate with a measured number. (frib.msu.edu)
