Although massive stars are crucial in solving the cosmic puzzle as they are key contributors of ionizing radiation, metals, cosmic rays and dust and, when they die, of neutron stars, black holes, and gravitational waves, many competing factors, are thought to influence their observed properties and challenge our understanding of how these stars evolve and contribute to the Universe.

The Massive Stars Commission (G2) of the IAU’s Stars and Stellar Physics Division regularly organizes a symposium, typically every 4 years, to present the latest research findings in the field, discuss the status of current research in massive stars, and chart the way forward for future research. The first meeting was in Argentina in 1971, and in the last decade we organized “Massive Stars: from Alpha to Omega” in Greece (2013), “IAUS 329: The Lives and Death Throes of Massive Stars” in New Zealand (2016), and “IAUS 361: Massive Stars Near and Far” in Ireland (2020, postponed to 2022 due to the pandemic).

Since the last symposium organized by the G2 commission (IAUS 361, 2022), the James Webb Space Telescope is dramatically changing our understanding of the early Universe. Important discoveries at high redshift have been made, including galaxies that are too massive for their age, systems with oxygen abundances typical of much later epochs of the Universe, and possible signatures of Pop III stars at z=10. Massive stars, through population synthesis codes, are critical to simulate the evolution and early chemical enrichment of galaxies in the infant Universe, and to analyse the observed spectra of these very high redshift systems.