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What a dying star's ashes tells us about the birth of our solar system – ScienceDaily



A dust grain forged in the death row of a far-away star was discovered by a research group led by the University of Arizona.

The discovery challenges some of the current theories of how dying stars frog the universe with raw materials for the formation of planets and ultimately the precursor molecules of life.

Tucked inside a chondritic meteorite collected in Antarctica, the little mirror actually represents stardust, probably knocked out in the space of an exploding star before our own sun existed. Although such grains are thought to provide important raw materials that contribute to the blend from which the sun and our planets form, they rarely survive the turmoil that comes with the birth of a solar system.

"As actual dust from stars, such presolar grains give us insight into the building blocks of our solar system," says Pierre Haenecour, lead author of the paper scheduled for further online publication at Nature Astronomy & # 39; s website on April 29. "They also give us a direct snapshot of the conditions of a star at the time this grain was formed." Double LAP-1

49 represents the dust grain the only known composition of graphite and silicate grains that can be traced to a specific type of star explosion called a nova. It remarkably survived the journey through interstellar space and traveled to the area that would become our solar system about 4.5 billion years ago, perhaps earlier, when it was embedded in a primitive meteorite.

Novae are binary star systems where a core residue of a star, called a white dwarf, is about to fade out of the universe, while its companion is either a low mass main sequence star or a red giant. The white dwarf then begins to seep material out of his inflated companion. As it acclimatizes enough new star material, the white dwarfs ignite in periodic outbursts violently enough to forge new chemical elements from the stellar fuel and deeply penetrate them into space where they can travel to new star systems and be incorporated into their raw materials

. . Shortly after the Big Bang, when the universe consisted only of hydrogen, helium, and traces of lithium, star explosions have contributed to the cosmic chemical enrichment, resulting in the abundance of elements we see today.

Utilization of sophisticated ion and electron microscopy facilities at UA's Lunar and Planetary Laboratory, a research group led by Haenecour analyzed the microbial dust grain down to the atomic level. The tiny messenger from outer space proved to be truly foreign – greatly enriched in a carbon isotope called 13C.

"The carbon monoxide compositions in everything we've ever sampled that came from any planet or body in our solar system typically vary by a factor of the order of 50," said Haenecour, who will join Lunar and Planetary Laboratory as assistant professor in the fall. "The 13C we found in the LAP-149 is enriched more than 50,000 times. These results further provide laboratory evidence that both carbon dioxide and oxygen-rich grain from Novae contributed to the building blocks of our solar system."

Although their Parent's stars no longer exist, the isotopic and chemical compositions and microstructure of individual stardust grains identified in meteorites provide unique limitations to the formation of dust and thermodynamic states in stellar currents written by the authors.

Detailed analysis revealed even more unexpected secrets: Unlike similar dust grains which are considered to have been forged into dying stars, LAP-149 is the first known grain consisting of graphite containing an oxygen-rich silicate inclusion.

"Our findings give us a glimpse of a process we could never witness of Earth," Haenecour added. "It tells us how dust grains form and move inside as they are expelled by nova. We now know that carbonaceous and silicate dust grains can form in the same nova ejecta, and they are transported across chemically separated dust clumps within ejecta, something which was predicted by models of novae, but never found in a sample. "Unfortunately, LAP-149 does not contain enough atoms to determine its exact age, so researchers hope to find similar larger specimens in the future.

"If we could dance these items one day, we could get a better idea of ​​what our galaxy looked like in our region and what triggered the formation of the solar system," said Tom Zega, scientific director of UA's Kuiper Materials Imaging and Characterization Facility. and Lecturer in Lunar and Planetary Laboratory and UA Department of Materials Science and Engineering. "Perhaps we are due to our existence for a nearby supernova explosion that compresses gas and dust clouds with its shockwave, ignites stars and creates star schools, similar to what we see in Hubble's famous" Pillars of Creation "image."

The meteorite containing the tip of stardust is one of the most pristine meteorites in the Lunar and Planetary Laboratory's collection. Classified as a carbonaceous condondrite, it is believed to be analogous to the material on Bennu, the target asteroid of the UA-led OSIRIS-REx mission. By taking a sample of Bennu and bringing it back to earth, OSIRIS-REx's mission team hopes to provide researchers with material that has seen little, if any, change since the formation of our solar system.

Until then, scientists rely on rare findings such as LAP-149, which survived blown from an exploding star caught in a collapsing cloud of gas and dust that would become our solar system and baked in an asteroid before falling to the ground .

"It's remarkable when you think of all the roads along the way that should have killed this grain," Zega said.


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