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The laws of the birth of stars in question

An international team led by CNRS researchers including a member of the LRA, the University of Grenoble Alpes and the CEA comes upset the idea that we had the formation of stars. The accuracy of the observations offered by the ALMA interferometer has made it possible to measure the quantity of massive star-forming cores in a very active far-away region of our galaxy, and thus to show that their proportion is higher than expected.

In space, behind the veil of nebulae, clouds of gas agglomerate and collapse on themselves to form the structures of the stars : the progenitor cores. They break up until a cluster of young stars of various masses appears, the distribution of which was described by Edwin Salpeter in the form of an astrophysical law in 1955.

Astronomers had observed that the proportion between massive and non-massive objects was the same in the groups of progenitor cores and those of newly formed stars. This suggested that the mass distribution of stars at birth, called IMF1, was simply the result of the mass distribution of the hearts that give birth to them, known as CMF2. But this conclusion is the result of the study of the molecular clouds closest to our solar system, which are not very dense and therefore not very representative of the cloud diversity of our galaxy.

The researchers in the collaboration focused on the cluster of W43-MM1 progenitor cores, whose structure is much more typical of the molecular clouds of our galaxy than those previously observed. Thanks to the unique sensitivity and spatial resolution of the ALMA antenna array installed in Chile, researchers have established a statistically robust core distribution over an unparalleled mass range, ranging from solar-like stars to stars 100 times more massive. Surprise : this distribution does not follow the law of 1955 ! Indeed, in the W43-MM1 cloud massive cores have been shown to be overabundant and heartbeats little under-represented.

Published in Nature Astronomy, these findings could challenge the widely accepted relationship between CMF and IMF, or even the assumed universality of the MFI. The scientific community will have to review its calculations on the formation of stars and eventually all estimates depending on the number of massive stars : chemical enrichment of the interstellar medium, number of black holes and supernovae ...

Source : CNRS National press release
Référence article : Nature Astronomy

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Figure : L’amas d’étoiles en formation W43-MM1, tel qu’observé avec le plus grand interféromètre millimétrique au monde, ALMA. Les très nombreux sites de formation d’étoiles, appelés cœurs et identifiés ici par des ellipses, témoignent de la forte activité de formation d’étoiles de cette région.

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© ESO/ALMA/F. Motte/T. Nony/F. Louvet/Nature Astronomy