Scientists have found the source of cosmic carbon, one of the main building blocks of life


Stars, like our Sun, not only provided a crucial environment for life during their lifetime, but it turns out that they also provide the main building blocks of life during their death. About 90% of all stars end up in white dwarfs while the others explode in supernovae.


As they collapsed, these stars scattered their ashes in the surrounding space through stellar winds enriched with chemical elements, including carbon, an element essential to all life in the Milky Way and in other galaxies.

Scientists have known for a long time that every carbon atom in the universe was created by stars, by the fusion of three helium nuclei. What they didn’t know was whether this carbon came from white dwarfs or supernovae.

Now, an international team of astronomers who analyzed white dwarfs in open star clusters in the Milky Way on the basis of astronomical observations concluded in a 2018 study at the WM Keck Observatory in Hawaii that dwarfs white are responsible for carbon.

The researchers achieved this by studying the relationship between the initial masses of stars and their final masses as white dwarfs, a relationship known as the initial-final mass relationship.

“From the analysis of the observed Keck spectra, it was possible to measure the masses of the white dwarfs. Using the theory of stellar evolution, we were able to trace back to the progenitor stars and derive their masses at birth, “said co-author of the new study Enrico Ramirez-Ruiz, professor of astronomy and astrophysics at UC Santa Cruz.

What they discovered was that the masses of newly discovered white dwarfs in the old open clusters were considerably larger than expected. “Our study interprets this peculiarity in the initial-final mass relationship as the signature of the synthesis of carbon made by stars of low mass in the Milky Way,” said lead author Paola Marigo at the University of Padua in Italy.

The researchers then discovered that stars with more than 2 solar masses also contribute to galactic carbon enrichment, unlike stars with less than 1.5 solar masses.

“Now we know that carbon comes from stars whose birth mass is not less than about 1.5 solar masses,” concluded Marigo. The study is published in the journal Nature astronomy.


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