It seems that most of the second generation stars were enriched with elements generated by supernovae from the first generation stars, born in clusters or binary systems. The discovery was made by researchers led by Tilman Hartwig of the University of Tokyo, who investigated the properties of these stars.
Different studies have shown that heavy elements, such as carbon, are produced inside stars, and that these elements are absent in those of the first generation, formed shortly after the Big Bang; those of the next generation, on the other hand, have a small amount of heavy elements, formed by the first stars.
Studying these stars helps researchers understand the “infancy” of the universe and, fortunately, second-generation stars are present in the Milky Way. For the study, the researchers studied some of them, as a way of trying to understand the physical properties of the first stars.
If the first stars were born in multiple star systems, elements from their supernovae must have been mixed and added into the new stars. So, to investigate their formation, they created a machine learning algorithm capable of differentiating whether the observed stars came from ejections from one or several supernovae, based on the elements of their spectrum.
They found that nearly 68% of observed low-metal stars have chemical signatures consistent with enrichment by previous supernovae. “The multiplicity of the first stars was predicted by numerical simulations, and there was no way to examine theoretical predictions with observations — until now,” Hartwig said.
According to him, the results suggest that most stars were formed in small clusters, and that several of the supernovae can contribute to the enrichment of the primordial interstellar medium. In other words, the findings indicate that the first stars were born with “neighbours”.
“The theory of the first stars tells us that the first stars should be more massive than the Sun, and the natural expectation was that the first star was born in a cloud of gas millions of times the mass of the Sun,” added Chiaki Kobayashi, a professor at the University of from Hertfordshire.
As the results suggest that the first stars were born inside clusters or binary or multiple star systems, they may have generated gravitational waves. For Chiaki, it may be possible to detect these waves through space missions or on the moon.
The article with the results of the study was published in the journal The Astrophysical Journal.
Source: The Astrophysical Journal; Via: Kavli Institute for the Physics and Mathematics of the Universe
