A new model describes how conditions inside the giant molecular clouds where star formation occurs, drive the similarities and subtle differences observed in the properties of sibling stars. Stars are not born in isolation, but rather in groups that are gravitationally bound together in star clusters. Stars that form this way are often found to share similar properties, such as age, chemical composition, and mass. However, astronomers have also noticed some small but significant differences between these sibling stars.

"The question is, what physical process can simultaneously produce both the similarities and differences of stars within the same cluster?", said lead author Dr. Jinjin Li, from the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) and the University of Tokyo, Japan.

In the paper published in the Astrophysical Journal, Dr. Li proposes a new model that explains the observed properties of sibling stars by taking into account the internal dynamics and chaotic nature of the molecular clouds where stars are formed.

The model describes how the gas in the molecular cloud undergoes a series of fragmentations, leading to the formation of multiple dense cores and ultimately to the birth of individual stars. Different regions within the cloud can experience different physical conditions, such as density, temperature, and chemical composition, which cause variations in the resulting stars.

For example, the most massive star in a cluster tends to form in the densest core of the cloud, and it is typically surrounded by smaller stars that formed in less dense regions. This distribution can be reproduced by simulating the highly dynamic processes occurring inside molecular clouds, such as supersonic turbulent motions, inflows, outflows, and fragmentation.

The model successfully reproduces a range of observational results, including the distribution of stellar masses, the ratio of low-mass stars, and the frequency of binary star systems. It also explains certain peculiarities in the observed initial mass function (IMF) - the distribution of stellar masses for a given cluster - and offers insights into why some massive stars in a cluster have lower metallicities (higher abundance of primordial helium) than expected.

"Our study highlights the role of the cloud environment and the chaotic processes during cloud evolution in shaping the properties of stellar clusters", said Dr. Li. "This work provides a more comprehensive understanding of the complex interplay between the internal dynamics of molecular clouds and the emergence of stellar populations in the universe."