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How a “Proto-Cluster” of Stars Forms

Using high-performance computing and an analytical model, researchers from IRFU have shown that certain properties of a stellar cluster are already "inscribed" in the gaseous proto-cluster that precedes it and that hosts stars while they form. Gravity and turbulence play a major role in this cluster.
Published on 20 May 2017
 How does a molecular cloud transform into a stellar proto-cluster—a cloud that is still gaseous but denser at its center—and then becomes a cluster of stars? Despite several challenges, astrophysicists try to reconstitute the "film" of the formation of a stellar cluster. In particular, the available computing power did not allow for correctly simulating the metamorphosis of the cloud into proto-clusters until recently. It was actually impossible to simultaneously describe the dynamics at a small scale and the global movement of gas on a large scale, although the latter leaves a footprint on the stars in the making.

Thanks to massively parallel computers and adaptive mesh refinement, astrophysicists from IRFU have succeeded in simulating the complete transformation of the molecular cloud into stellar clusters. In particular, they have provided evidence for a gaseous proto-cluster whose structure is maintained during star formation.

From observations, the scientists were able to highlight a remarkable property of these gaseous proto-clusters: their mass is proportional to the square of their radius, for total masses varying from one hundred to ten thousand solar masses.

They have also developed a simplified analytical model that describes the main physical mechanisms at work. With this model, they were able to successfully reproduce the relationship between the mass and the radius of the cluster, as deduced from the observations, as well as the shape of the proto-clusters.

The next step will be to introduce the feedbacks of stars on their environment in computer simulations, such as stellar winds or supernova explosions. The evolution of the cluster will be reconstructed in a ways that are even closer to reality.

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