ALMA WITNESSES STAR BIRTH BEYOND THE EDGES OF THE MILKY WAY
Credits: A. Traficante et al.
Rome, 22 April 2026 - An international team, led by the Italian National Institute for Astrophysics (INAF), has mapped for the first time—with unprecedented resolution — the mass distribution of the gas and dust clumps from which new stars will ignite (the so-called core mass function or CMF) in a star-forming region outside the Milky Way. The study, published in Nature Communications, focused on the 30 Dor-10 region within the Large Magellanic Cloud and was made possible by highly detailed observations conducted with the ALMA radio telescope (Atacama Large Millimeter/submillimeter Array) in Chile.
To achieve this result, the research team pushed ALMA to the limits of its capabilities for this type of study, obtaining an extreme angular resolution of 0.05 arcseconds—equivalent to spotting a one-euro coin from a distance of 100 km. This precision allowed the team to distinguish details as small as 2,000 astronomical units (2,000 times the Earth-Sun distance) at approximately 160,000 light-years from us. Within 30Dor-10, 70 dense gas and dust cores—the precursors to stars—were identified, distributed across four protoclusters. To eliminate contamination caused by the ionised gas typical of such extremely dense and active regions, it was essential to combine ALMA data with observations from the Hubble and James Webb space telescopes, which also confirmed that these cores are still in a relatively early stage of their evolution.
“We are truly excited about the results achieved with this study. Thanks to ALMA, studying core masses in our Galaxy is becoming almost ‘routine,’ suggesting in particular that the mass of our cores seems to evolve, especially in high-mass regions,” comments Alessio Traficante, a researcher at INAF in Rome and lead author of the paper. “Until now, no one had attempted to push this type of research into extra-galactic regions, which require significantly higher resolution and sensitivity than studies conducted within the Milky Way (which are already particularly demanding). The identification of more than 70 cores in 30Dor-10 was by no means guaranteed, considering we were observing an environment with an interstellar medium whose characteristics are profoundly different from those found in the main massive star-forming regions of our Galaxy. We had no idea what to expect before seeing the stunning images obtained by ALMA at a scale of 2,000 astronomical units in this region”.
A comparison between the mass distribution of the cores observed in the Large Magellanic Cloud and those in the Milky Way during their initial stages has shown that both follow a similar pattern, known as Salpeter’s Law, despite the vastly different environmental conditions in this region regarding metallicity, turbulence regimes, and ionisation of the interstellar medium. The discovery suggests that the initial fragmentation mechanisms of molecular clouds are independent of the surrounding environment. Even though, in such extreme regions, the initial mass function (IMF) of stars can evolve with an excess of massive stars, the early phase of core formation seems to remain consistent with observations in our Galaxy—namely, that these young cores can continue to accrete mass over time.
This work, linked to ALMA Large Programs such as ALMA-IMF and ALMAGAL, paves the way for a systematic study of star formation in other galaxies, using techniques and methodologies previously applied only within the Milky Way. This result finally allows us to begin verifying whether the laws governing the birth of stars remain the same across different, more remote environments throughout our Universe.
RELATED JOURNAL ARTICLE:
“The fragmentation properties of massive star-forming regions in 30Dor-10 at 2000 au resolution”, A. Traficante, M. J. Jiménez-Donaire, R. Indebetouw, T. Wong, A. Nucara, R. Klessen, P. Hennebelle, U. Lebreuilly, C. Mininni, S. Molinari, E. Sabbi, J. Soler, published online in Nature Communications.
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The image shown in this webpage can be used to cover this topic. Please include credits as follows.
Figure 1: The image shows the 30Dor-10 region in the Large Magellanic Cloud, as seen by the James Webb Space Telescope using a filter that highlights emission associated with ionised gas. The box on the left represents one of the two clusters considered in this study, "Clump 52," as seen by ALMA before these new results, at a resolution of approximately 20,000 astronomical units. The box on the right shows the stunning new images at 2,000 astronomical units, where the cluster can be seen separating into two protoclusters. The brightest and most massive one is in the bottom-right box. Credits: A. Traficante et al.
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