Every second, a star dies in the universe. But these star beings not only completely disappear, the stars always leave something behind.
Some stars explode into a supernova, turning into a black hole or neutron star, while most stars become white dwarfs, a nucleus of the star it used to be. However, a new study reveals that these white dwarfs contribute more to life in the cosmos than previously believed.
The study, published Monday in the journal. Astronomy of nature, suggests that white dwarf stars They are the main source of carbon atoms in the Milky Way, a chemical element known to be crucial to all life.
When stars like our own Sun, a yellow dwarf star, run out of fuel, they become a white dwarf. In fact, 90 percent of all stars in the universe end up as white dwarf stars.
White dwarfs are dense, hot stellar remains with temperatures reaching 100,000 Kelvin. Over time, billions of years, these stars cool and eventually darken as they lose their outer material. However, just before they collapse, their remains are transported through space by winds originating from their bodies.
These stellar ashes contain chemical elements such as carbon.
Carbon is the fourth most abundant chemical in the universe and is a key element in the formation of life, since it is the basic component of most cells.
All the carbon in the universe originated from stars, therefore the phrase that we are made of stars is not only poetic but rather accurate. However, astronomers could not agree on which type of star is responsible for diffusing the most carbon in the cosmos.
The scientists behind the new study used observations of white dwarfs in open star clusters, groups of a few thousand stars formed at roughly the same time, in the Milky Way by the WM Keck Observatory in Hawaii in 2018.
They measured the initial-final mass ratio of stars, which is the ratio of the masses of stars when they first formed to their masses as white dwarfs.
In general, the larger the star, the more massive a white dwarf will be. However, the study found that the masses of the stars as white dwarfs were larger than scientists had anticipated considering their initial mass when they were first formed.
“Our study interprets this twist in the initial-final mass ratio as the signature of carbon synthesis made by low-mass stars in the Milky Way,” Paola Marigo, researcher at the University of Padua in Italy, and lead author of The study said in a statement.
The team of scientists concluded that stars of more than 2 solar masses also contributed to galactic carbon enrichment, while stars of less than 1.5 solar masses did not.
“We now know that carbon comes from stars with a birth mass of not less than about 1.5 solar masses,” said Marigo.
The new study suggests that carbon was essentially trapped in the raw material that formed the Solar System 4.6 billion years ago.
Summary: The initial-final mass ratio (IFMR) links the birth mass of a star to the mass of the compact remnant remaining at its death. Although the relevance of the IFMR in astrophysics is universally recognized, all its details have not yet been resolved. A new analysis of some white carbon-oxygen dwarfs in old open clusters of the Milky Way led us to identify a knot in the IFMR, located in an initial mass range, 1.65 ≲METERme/ /METER⊙≲ 2.10. The peak of the white dwarf mass fold of approximately 0.70−0.75 METER⊙ is produced by stars withMETERme≈ 1.8−1.9METER⊙, corresponding to ages of approximately 1.8 to 1.7 Gyr. Interestingly, this peak coincides with the initial mass boundary between low-mass stars that develop a degenerate helium nucleus after central hydrogen depletion, and intermediate-mass stars that prevent electron degeneration. We interpret the IFMR twist as the signature of the formation of carbon stars in the Milky Way. This finding is critical to limit the evolution and chemical enrichment of low-mass stars, and their impact on the spectrophotometric properties of galaxies.
