Collisions of Dead Stars Spray Heavy Elements Throughout Small Galaxies

Caltech News tagged with “astronomy + exoplanets + JPL + planetary_science”

Caltech scientists have found, for the first time, that merging pairs of neutron stars—the burnt-out cores of stars that have exploded—create the majority of heavy elements in small “dwarf” galaxies. Heavy elements, such as silver and gold, are key for planet formation and even life itself. By studying these dwarf galaxies, the researchers hope to learn more about the primary sources of heavy elements for the whole universe. The origin of the majority of the heaviest elements of the periodic table, including 95 percent of all gold on Earth, has been debated for decades. It is now known that the heaviest elements are created when the nuclei of atoms in stars capture particles called neutrons. For most old stars, including those residing in the dwarf galaxies in this study, the process happens rapidly and is therefore called an “r-process,” where the “r” stands for rapid.There are two favored sites where the r-process is theorized to occur. The first potential site is a rare type of a stellar explosion, or supernova, that produces large magnetic fields—a magnetorotational supernova. The second site is at the merger, or collision, of two neutron stars. In August 2017, the National Science Foundation-funded Laser Interferometry Gravitational-wave Observatory (LIGO) and other ground-based telescopes detected one such neutron star collision in the act of creating the heaviest elements. But witnessing just one event doesn’t tell astronomers where the majority of these materials are created in galaxies. To look at heavy element production in galaxies as a whole, the Caltech researchers studied several nearby dwarf galaxies using the W. M. Keck Observatory on Maunakea in Hawaii. While our Milky Way is considered about average in size as far as galaxies go, these dwarf galaxies, which orbit around the Milky Way, have about 100,000 times less mass in stars than the Milky Way. The scientists looked at when the …

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