Extreme conditions for star formation in local low metallicity environments

The challenge

Every star, including our own Sun, begins its life inside a cold cloud of gas and dust. Stars are not born in isolation; they form within the giant molecular clouds that contain dense clumps and compact cores where new stars are born. Although astronomers have made significant progress in understanding star formation in the Milky Way, one of the biggest challenges is explaining how the physical and chemical conditions within these small-scale structures are linked to the evolution of their parent molecular clouds. How do temperature, density, radiation, chemical composition, and metallicity (the abundance of elements heavier than hydrogen and helium) – work together to determine when and where stars are born?

This question becomes even more intriguing in the outer regions of the Milky Way, where molecular clouds have significantly lower metallicity than those closer to the Galactic Centre. The low-metallicity means less dust and fewer heavy elements to cool the gas, while ultraviolet radiation penetrates deeper into molecular clouds, destroying carbon monoxide (CO) and creating large reservoirs of “CO-dark” gas (molecular gas that is not easily traced by the commonly used CO molecule). These conditions closely resemble those in galaxies billions of years ago, when the Universe was forming stars at its highest rate. Unlike distant galaxies, however, molecular clouds in the outer Milky Way are close enough to be observed with much higher sensitivity and spatial resolution, allowing us to study the star formation process in unprecedented detail.

This project, funded by the Polish National Science Centre (NCN), will investigate how metallicity and the local environment influence star formation across a wide range of spatial scales—from dense cores and clumps to entire molecular clouds. By connecting the small-scale physics and chemistry of stellar birth with the large-scale evolution of molecular clouds, our research will improve our understanding of how stars and galaxies evolved across cosmic time.

Our approach

The project will use observations from two state-of-the-art submillimetre telescopes in the Atacama Desert, Chile—the 12-metre Atacama Pathfinder Experiment (APEX) and the 6-metre CCAT Fred Young Submillimeter Telescope (FYST). The research group will analyse molecular data obtained as part of the APEX Large Programme “Outer Galaxy High Resolution Survey (OGHReS)” and, in the near future, obtain complementary atomic gas tracers through the CCAT consortium. By studying the emission from molecules (e.g. hydrogen cyanide) and atoms (e.g. carbon), present in molecular clouds, the research group will constrain the chemical composition, and physical conditions and processes taking place in the birthplaces of stars.

Expected impact

This project will provide a deeper understanding of how star formation operates in low-metallicity environments by tracking variation of molecular abundances across the outer part of our Galaxy. Moreover, the project aims to detect a significant amount of “CO-dark gas” in these low-metallicity regions, produced by the destruction of molecules due to ultraviolet radiation. The research will also use state-of-the-art models of molecular clouds to study how ultraviolet radiation and cosmic rays shape the physical conditions of star-forming gas in the outer Milky Way, providing a framework that can be applied to other galaxies, such as the Large and Small Magellanic Cloud.