We live near a fusion reactor in space that provides all our heat and light. That reactor is also responsible for the creation of various elements heavier than hydrogen, and that’s true of all stars. So, how do we know that stars are element generators?
Many clues lie hidden in stellar spectra, since they contain fingerprints of various elements cooked up by the stars. Hints about the creation of carbon and oxygen in particular lay hidden for years in a data set taken in a search for planets around nearby stars. Astronomers have suggested that such stars could be promising places to look for exoplanets.
Thanks to a brainstorm by astronomer Darío González Picos of Leiden University in the Netherlands, he and a research team examined high-resolution spectra of nearby stars to look for rare isotopes of carbon and oxygen. The team studied 32 M dwarf-type stars, which are among the most common in the Galaxy.
M dwarf stars live for a long time on the main sequence, which is the period when a star fuses elements in its core. The atmospheres of these stars preserve the signatures of their chemical evolution from birth to their current state. The stars in the study showed rare isotopes of carbon and oxygen, revealing new details about their evolution.
The result of the team’s work represents a step forward in understanding the creation of elements and how they get dispersed during stellar evolution.
### Stellar Seeding of Elements
Carbon and oxygen are highly abundant in the Universe. We are carbon-based life forms, as is all life on our planet, which itself contains carbon in its makeup. We breathe oxygen, generated by other life forms on Earth. So, it’s natural to wonder how these two essential elements came about in the process of stellar evolution.
Understanding this means comprehending the complexities of element-making processes in stars.
“Nuclear fusion in stars is a complex process and is just the starting point of chemical evolution,” said Darío González Picos, who headed the research. This process, called stellar nucleosynthesis, occurs in all stars. Our Sun, for example, fuses hydrogen to make helium and will continue to do so for several billion years.
Eventually, the Sun will run out of hydrogen in its core and begin to fuse helium into heavier elements, such as isotopes of carbon and oxygen. At that point, it will become a reddish star, expelling its elements into space through strong stellar winds.
Stars much more massive than the Sun follow a similar path but go on to create even heavier elements when they explode as supernovae. Essentially, stars are part of a colossal cosmic recycling project, enriching their galaxies with material to form new stars and planets.
### Finding the Rare Fingerprints
González Picos collaborated with Ignas Snellen and Sam de Regt to detect and analyze the chemical fingerprints in starlight by using isotopes of carbon and oxygen. These isotopes are different varieties of those elements, distinguished by the number of neutrons in their atoms.
For example, on Earth, 99% of carbon atoms have 6 neutrons, but a small fraction has 7. The team successfully measured these isotope ratios for both carbon and oxygen in 32 nearby stars with unprecedented precision.
They accomplished this by sifting through data archives from the Canada-France-Hawai’i Telescope on Mauna Kea in Hawai’i. The data included stars with effective temperatures between 3000 and 3900 K, exhibiting strong signals for heavier elements (high metallicity in their atmospheres).
*Artist’s impression of isotopes in a red dwarf star.*
“This finding confirms what some models of galactic chemical evolution have predicted and now provides a new tool to rewind the chemical clock of the cosmos,” said the team.
“The observations were originally made for a completely different reason than the one we are using them for now,” noted Snellen. “It was entirely Darío’s idea to use the high-resolution spectra, which were initially intended for discovering planets, for this isotope research with impressive results.”
### Unlocking Cosmic Mysteries
As González Picos points out, this research offers another way to use stellar chemistry to trace various types of evolution in the Universe.
“This cosmic detective story is ultimately about our own origins, helping us to understand our place in the long chain of astrophysical events, and why our world looks the way it does,” he said.
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### For More Information
– “Rare Isotopes in Our Neighboring Stars Provide New Insights in the Origin of Carbon and Oxygen”
– “Chemical Evolution Imprints in the Rare Isotopes of Nearby M Dwarfs”
https://www.universetoday.com/articles/the-suns-red-dwarf-neighbors-provide-clues-to-origins-of-carbon-and-oxygen