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Sodium aids metallofullerene formation in stellar outflows

Ancient meteorites at times possess grains of graphite that pre-date the birth of the solar system. Past research found these grains are often mysteriously enriched with a form of neon known to be a byproduct of supernovae. Now scientists have discovered soccer-ball-like molecules known as buckyballs may act like cages that entrapped this neon within these grains, report findings detailed in the Proceedings of the National Academy of Sciences. The research should yield insight into how carbon stardust forms, the material that life on Earth is ultimately based on.

Past research found that pre-solar graphite particles in ancient meteorites carry the isotope neon-22. This neon results from the radioactive decay of the relatively short-lived isotope sodium-22, which is created by explosive nucleosynthesis during supernovae. This suggests this isotope gets rapidly trapped within carbon as it condenses in the aftermath of an exploding star, but investigators were uncertain how this could happen.

To discover how carbon might encapsulate this sodium isotope, scientists used lasers to blast a carbon rod laced with sodium in the presence of hydrogen and oxygen at Florida State University’s National High Magnetic Field Laboratory, matching condensing carbon conditions in stellar outflows. They discovered this generated buckminsterfullerene, a molecule also known as the buckyball made up of 60 carbon atoms bound together to form a ball in a pattern matching the panels on soccer balls.

“Fullerenes have been recently detected in many astrophysical environments in space,” says researcher Paul Dunk, a nano-carbon chemist at Florida State University in Tallahassee. “They are popping up everywhere in circumstellar and interstellar space.”

In addition, these experiments created metallofullerenes — buckyballs that encapsulate metals and other elements, in this case sodium — just as readily as their empty cousins. The sodium apparently helped trigger the formation of these metallofullerenes — laser-blasting regular carbon rods in the presence of neon-rich gas did not result in any metallofullerenes full of neon.

These findings help solve the long-standing mystery of how anomalous neon makes its way into ancient carbon grains. Furthermore, many other elements may trigger metallofullerene formation, suggesting that many different kinds of metallofullerenes could enrich stardust and help explain other celestial puzzles.

“The next challenge is to observationally detect metallofullerenes in space and investigate what other unsolved astrophysical problems metallofullerenes can explain,” Dunk says. “We have simulated their general spectroscopic fingerprints to aid astronomers in the search.”

Categories: Astronomy
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