Cosmic dust demystifies the origins of our solar system

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Feb 4, 2017

Stardust has finally solved a mystery as unfathomably old as the creation of our solar system.

Scientists from all over Europe collaborated at Italy's underground Laboratory for Underground Nuclear Astrophysics (LUNA) in a study that ended up illuminating more of the mystery behind the nebulous origins of our solar system. Published in the journal Nature Astronomy, this study has chemically linked cosmic dust found in meteorites to the immense dust cloud that astronomers believe our Solar system emerged from some 4.6 billion years ago. This stellar finding glows especially brightly because most of the grains that were thought to swirl in the chaos of that antediluvian dust cloud were destroyed as space rocks and planets were born.

"The long-standing question of the missing dust was making us very uncomfortable: it undermined what we know about the origin and evolution of dust in the Galaxy," said team lead Dr. Maria Lugaro of Hungary's Konkoly Observatory. "It is a relief to have finally identified this dust thanks to the renewed LUNA investigation of a crucial nuclear reaction."

Evidence of specific chemical reactions identified the dust as originating from Asymptotic Giant Branch (AGB) stars, celestial bodies 6-8 times the size of the sun that were in their death throes at the time of the embryonic solar system. After a star has been in the red giant phase for a stretch of time, its helium core contracts and heats up at an astonishing rate, eventually skyrocketing to temperatures hot enough to ignite what is called the helium flash. The star becomes a red giant again — entering the AGB phase — after the helium in its core eventually burns out. As these ancient stars degenerated, their outer layers were blown off into space and the refuse is believed to have accumulated into a cloud of cosmic gas and dust.

Artist’s rendering of an interstellar dust cloud.

Nuclear reactions specific to AGB stars left a lasting mark on the chemical composition of the dust grains for billions of years. Nuclear physicists were also surprised to determine that there had been twice as many fusion reactions between protons and type of oxygen known as 17O that is much heavier than that floating in the Earth's atmosphere (and nowhere near breathable). Proton-capture nucleosynthesis, in which protons are 'captured' and consumed by the nucleus of an atom, was one of the reactions they sought out the most. Stardust grains have the effect of such reactions imprinted in their astral DNA.

"It is a great satisfaction to know that we have helped to solve a long-standing puzzle on the origin of these key stardust grains," said UK team lead Professor Marialuisa Aliotta of the University of Edinburgh's School of Physics and Astronomy. "Our study proves once again the importance of precise and accurate measurements of the nuclear reactions that take place inside stars."

(via Science Daily)