Stars are known to be bonfires where all the elements of the periodic table melt. In particular, carbon owes its existence to the fusion of three helium nuclei, but there is no consensus on the specific type of star involved in the process. A new study by international researchers sheds a little light on this unknown with their analysis of white dwarfs in open star clusters in the Milky Way.

90% of the stars become white dwarfs when, in their final phase, they gradually cool down and turn off. They have had a fundamental role in the creation of carbon and, therefore, in the appearance of life in the Milky Way and in other galaxies, the new research assures.

The ratio of the initial and final mass (when they are already white dwarfs) of the stars is a key parameter for astronomers to understand their life cycle. Normally, the bigger the star is at birth, the bigger the white dwarf that is created when it dies, but these scientists have detected an alteration in that proportion in the case of the stars they have analyzed.

“Our study interprets this alteration in the relationship of the initial and final mass as the signature of the carbon synthesis generated by low-mass stars in the Milky Way,” says the study’s lead author, Paola Marigo, from the University of Padua in Italy.

It should be noted that when analyzing this change in the ratio of the mass, the astronomers concluded that the stars that have an equivalent to twice the solar mass-produce new carbon atoms inside that then spread through space due to the stellar wind. 

In this way, it can be said that white dwarfs that double the mass of the Sun contribute to the galactic enrichment of carbon, while in the case of those that have an equivalent to 1.5 times that of the star king, the process does not occur in sufficient quantity. So “we now know that carbon came from stars that had at birth a mass of at least 1.5 solar masses,” says Marigo.