Starbursts and slow burns

This is one of 74 nearby galaxies whose stellar nurseries were recently observed by the Atacama Large Millimeter/submillimeter Array, or ALMA, in an astronomical census called Physics at High Angular resolution in Nearby GalaxieS (PHANGS). So far, around 100 000 of these stellar nurseries have been imaged in over 750 hours of observation. ALMA’s remarkable sensitivity provides data at high enough resolution to study these regions in detail, and shows that some are bursting with new stars, while others evolve more gradually.

This anticipated diversity in the process of how stars form was the motivation behind this enormous effort. There have long been theories that aimed to explain how and why these differences might occur, some involving the characteristics of the home galaxy itself — properties such as size, age, and internal dynamics — but our lack of high-resolution data had been an obstacle to testing them.

The vast quantity and variety of data yielded by PHANGS are already helping astronomers to understand more, even though the census is only a third complete. The project aims to observe a total of about 300 000 stellar nurseries and by the end it should significantly advance our understanding of how a galaxy’s properties influence the way in which it forms new stars.